The Trials of Life
Encyclopedia
The Trials of Life: A Natural History of Behaviour is a BBC
nature documentary
series written and presented by David Attenborough
, first transmitted in the UK
from 4 October 1990.
A study in animal behaviour, it was the third in a trilogy of major series (beginning with Life on Earth) that took a broad overview of nature, rather than the more specialised surveys of Attenborough's later productions. Each of the twelve 50-minute episodes features a different aspect of the journey through life, from birth to adulthood and continuation of the species through reproduction.
The series was produced in conjunction with the Australian Broadcasting Service
and Turner Broadcasting System
Inc. The executive producer was Peter Jones and the music was composed by George Fenton
.
Part of David Attenborough's 'Life' series, it was preceded by The Living Planet
(1984) and followed by Life in the Freezer
(1993).
The sequence of chimpanzee
s hunting colobus monkey
s was only possible through the efforts of Hedwige and Christophe Boesch
, who had spent five years studying the apes in the Ivory Coast
forests of West Africa
.
Meanwhile, a bivouac
of army ant
s in Panama
was able to be filmed internally with the aid of a medical endoscope
. Furthermore, a new type of camera lens enabled tree ants to be filmed in enlarged close-up just in front of Attenborough — with both subjects in sharp focus. This gave the illusion that the insects were much larger than their actual size.
Filming critical moments in the life of a herd of elephant
s necessitated the expertise of Cynthia Moss
, who had devoted 25 years to researching the animals in Kenya
. She was able to advise the production team on the right moments to film specific events.
The camera team had only one chance to film a 60,000-strong flock of wader
s flying over David Attenborough's head in Norfolk
, and the RSPB
was enlisted to predict their flightpath. By contrast, the Florida scrub jay
s couldn't have been more co-operative: since the particular group being filmed had been studied closely and were used to humans, a bird could land on Attenborough's hand right on cue.
The inside of a termite
mound proved especially challenging for Attenborough: it was so cramped that he could only face in one direction. He therefore had to slowly crawl backwards out of shot when performing re-takes.
Behaviour seen for the first time included the sequence that was eventually selected to illustrate the series' DVD cover: that of a killer whale
pouncing on a colony of sea lion
s on a Patagonia
n beach and 'playing' with its young prey before consuming it. This meant some risks being taken by the cameramen, as they placed themselves in the water just feet away from the creatures in order to obtain close-ups of an attack run.
Broadcast 4 October 1990, the first episode examines the various methods by which creatures come into the world. Attenborough’s opening statement alludes to the annual spawning of the Christmas Island red crab
, of which there are estimated to be some 120 million. The exercise is all the more hazardous since the species is a land crab, and the eggs have to be deposited in the sea — where the most ancient animals on the planet still live and breed. One of the most prolific aquatic egg producers is the giant clam
, but some land animals also lay vast quantities, and the mantis
is one example. In the Western United States
, Attenborough observes a wasp
that digs a burrow, conceals it, and stocks it with fresh caterpillar
s for her emerging young. The grubs of another start life inside caterpillars, and eat the unsuspecting hosts
. The problems of larger animals are illustrated by snow geese
in the Arctic
, which have to defend their eggs from arctic fox
es. The process of embryo
nic growth inside the egg, from laying to hatching, is shown in detail. The malleefowl
warms its eggs with rotting leaves
, and Attenborough demonstrates the care with which it regulates them by adding sand to its mound — to have it kicked back in his face. The sea louse is a crustacean
that commits suicide: its grubs consume so much of the mother’s energies that she dies after birth. Mammal
s shown giving birth to fully formed young include wildebeest
, antelope
, sea lion
s and chinchilla
s.
as an animal that experiences a compressed childhood, being abandoned after three weeks and left for up to another eight alone, while it becomes large enough to be able to swim. For tern
s, there is safety in numbers as the dense population works together to drive out marauding gull
s. The snow geese in the Russia
n Arctic show intense devotion as they escort their goslings by foot to the coast some 50 kilometres away. Scorpion
s carry their young on their backs, while a shrew
will leave hers under a stone while she goes to feed. The eider duck
is one creature that shares responsibility for its offspring: females regularly supervise the ducklings of others in a group. The mara
is another that uses a crèche
system, as does the bat
, whose nurseries can be up to a million strong. The Florida scrub jay has a complex system of raising young known as cooperative breeding
, where young stay on as helpers at the nest of their parents. Such behaviour is exhibited on a larger scale by elephants, where all females take an interest in raising a single calf. A chimpanzee’s childhood is socially complicated, as an individual must learn how to behave towards others, as well as master the use of tools. Albatross
es must be accomplished fliers as soon as possible — chicks are shown being hunted by tiger shark
s.
n rainforest
, where the proliferation of animal and plant life does not necessarily make it easy to find food. Some leaves are poisonous, and so those that eat them have to be careful. Other plants use food (or nectar) as a bribe to get their pollen
transported, and several species of hummingbird
have developed exclusive relationships with certain of them. Fruit is also on offer, again as a means of reproduction, and creatures such as squirrel monkey
s eat little else. Meanwhile, parrot
s and macaw
s take kaolin
as an antidote to their diet of toxic seeds. Attenborough witnesses a 60,000 strong flock of knot
and dunlin
suddenly take advantage of a low tide to feed on tiny mud-dwelling molluscs. Barracuda
hunt small fish, and drive shoals of them into bays to be eaten by pelican
s, which are besieged by gulls that attempt to steal their catches. One species of gecko
is able to differentiate between worker termite
s and the more dangerous soldiers. The web of the orb spider
is hailed as one of the most elegant food catching devices, and the methods of two others, nephila
and its kleptoparasite
visitor, argyrodes
, are explored in detail. Finally, tropicbirds, their crop
s full with food en route back to their nests, are ambushed in mid-air by a group of frigatebird
s, whose aim is to make them surrender their cargo.
Broadcast 25 October 1990, this episode looks at those that hunt other creatures and ways of avoiding capture. Attenborough is attacked by a pair of skua
s as he approaches their nest, which demonstrates this particular bird's aggressive behaviour, both when taking food and defending its young. Off the shores of Patagonia, the same group of killer whales returns each year to ambush sea lion
pups, which stray out of the safer shallow waters. Having grabbed their prey, they take it back out to sea and 'play
' with it for some time before killing it. Poison
can be used both as a weapon and a deterrent, such as by the viper
and tomato frog
respectively. Some animals advertise their defensive measures in advance, in case deployment occurs too late. Among them are the skunk
, which discharges an appalling smell, and some salamander
s that display their toxicity by remaining stationary, with their warning markings
visible. Several species of stick insect
and their elaborate camouflage are shown. However, none of these methods of protection pose problems to army ant
s, which can subdue any of their prey, simply by virtue of their size and vast numbers. The Harris hawk
is unusual, since it hunts in teams, and a group of six are shown practising their skill in the desert
of New Mexico
. The final sequence depicts a troop of chimpanzee
s displaying strategy and co-ordination as it successfully pursues colobus monkeys through a forest in the Ivory Coast.
at dusk, by describing some of the species that don't rely on sight
. The spotted hyena
uses its acute sense of smell
to guide it while it hunts nocturnally, while galago
s urinate on their hands so they can completely mark their movements. Some animals use echolocation
and these include swiftlet
s, bats and river dolphin
s. By contrast, electric eel
s use fields of electricity to sense their environment. During the hours of daylight, other methods are employed: the rufous elephant shrew
, with its carefully cleared network of pathways, has a sharp mental picture of its habitat — even knowing the various shortcuts with which to evade capture. Attenborough visits the Sahara
to illustrate a species that makes the longest overland journey of any insect: cataglyphis
, an ant that uses the sun
's position to enable it to return to its nest in a straight line. Lobster
s in the Bahamas
are shown marching in columns to escape stormy waters. In its search for perpetual daylight in which to fish, the Arctic tern
makes a 19,000-kilometre journey from one end of the Earth
to the other. The albatross
is highlighted as one of the most skilled navigators: it can travel up to 1300 kilometres over sea in search of food for its chicks, and still find its way back to the nest. Finally, Attenborough stands on a waterfall in Ireland
to tell of the three-year, 10,000-kilometre journey made by elver
s.
, an elaborate construction that has its own air conditioning system. Silk
is such a valuable commodity that those that can't make it steal it instead. The hermit hummingbird
uses it to attach its nest to the underside of a leaf, while the Indian tailorbird
stitches two leaves together. However, the expert in complex nest-building is the weaverbird which makes its abode from over 1,000 strips of grass that are perfectly interwoven — and dismantling it if it fails to attract a mate. The beaver
is responsible for one of the biggest animal dwellings: its wooden lodge that rises from the river bed stays in place from one generation to the next, and so requires constant maintenance. Some stingless bee
s use their wax
and the resin
of tree bark to create labyrinthine structures containing various compartments. Mud
is also used by several creatures, such as the potter wasp
and the cliff swallow
. The termite
s' intricate creations allow for security, heating, air conditioning, self-contained nurseries and gardens, and sanitation systems. Attenborough hails the species as the consummate home maker, and explores a 15-foot colony in West Africa that contains 1.5 million insects: he crawls right inside to examine its method of ventilation.
Broadcast 15 November 1990, this episode focuses on those species that co-operate and depend on (or exploit) others. Spotted deer
follow langur monkey
s as they travel from tree to tree, eating any leaves that get dropped from above. In return, the deer serve as a lookout when the primates are feeding on the ground. Underwater, a hermit crab
is shown adding sea anemone
s to its shell in order to protect itself from attack by an octopus
, and a goby
assists a virtually blind shrimp
. Flea
s, lice
and mite
s are parasites
: they share no mutual partnership and instead take advantage of creatures for food or shelter. However, parasites have their predators, and an example are the finch
es of the Galápagos Islands
that clear the resident giant tortoise
s of their tick
s, and oxpecker
s, which do the same for giraffe
s in Africa (and even use its fur to line their nests). Some fish regularly clean others, and wrasse
and shrimp appear to specialise in this regard, as do remora
, which permanently hang on to their hosts. One parasite that grows inside its host is the fluke
, and one is shown gestating inside a snail
, having previously been unknowingly eaten. Because it needs to transfer to a bird's gut to develop further, it causes the snail to advertise its presence to allow itself to be consumed — thus completing the circle. However, some microscopic creatures inhabit the stomachs of large herbivores in order to break down the cellulose of their diet, thereby aiding their digestion.
by placing a stuffed specimen nearby, only to have it speared by its opponent's bill. The midas cichlid
on the other hand, has no weapons to speak of, and so uses its mouth to hold on for trials of strength. By contrast, the forelegs of a mantis shrimp
are powerful enough to crack the shell of another crustacean
: therefore disputes or courtship are fraught with danger. Animals that possess lethal food-gathering weapons usually don't use them against one another, as neither side wishes to risk death. For example, one venomous snake
will aim to floor the other, rather than bite. Wolves and big cat
s largely use snarls and body posture to convey their threat. There are no holds barred between rival zebra
s: kicking and biting is employed until a victor emerges, whereas giraffes slam their necks against each other. Normally peaceful mountain gorilla
s are shown squabbling when play gets out of hand, and one of them communicates real fright by urinating uncontrollably. Large herbivore
s that have horns or antler
s are naturally inclined to use them to assert their dominance over the females in a herd. Duelling male ibex and Alaskan bull moose
undergo some of the most ferocious engagements — sometimes to the death.
is contrasted with whooper swan
s landing in Scotland
after a 1,600-kilometre journey from Iceland
. Once arrived, they must battle for territory with those already there, and pairs or families are usually victorious. Attenborough uses a group of farmyard chicken
s to demonstrate a pecking order
. Caciques
are shown cooperating to deter predators, despite their fighta amongst themselves to establish a pecking order. A pride of lion
s is shown co-operating to subdue a buffalo
. Afterwards, each animal peacefully awaits its turn at the carcass. Baboon
s live in troops of up to 150, and their complex dominance hierarchy
is examined in detail. Vampire bat
s display reciprocal altruism
by regurgitating blood
for any neighbour that has missed out on a night's feeding. Dwarf mongoose
s live in family groups of around a dozen. While some look for food or sleep, others are always posted on the lookout for predators and quickly raise the alarm if necessary. Meanwhile, some of the most extreme co-operation is demonstrated by the underground naked mole rat
, whose 80-strong clusters are divided into workers (who tunnel perpetually), soldiers (who only act when danger threatens), and a single queen for breeding. Leafcutter ant
s are shown transporting their food deep below ground: it has to be planted in a special fungus
to convert its indigestible cellulose
into something edible, and each stage of the operation is carried out by a different caste
of individuals.
Broadcast 6 December 1990, this episode concentrates on animal communication
. In Kenya
, Attenborough accompanies a tribesman who calls to a honeyguide
, which in turn answers him and leads the pair to a bees' nest. The tribesman extracts the honey
, and some is left to reward the bird. African hunting dog
s are shown hunting gazelle
s, of which the target is the individual that leaps
lowest. Lark
s evade merlin
by sending a similar message: by continuing to sing while being chased, it tells the pursuer that its prey is fit and therefore will be difficult to catch (see handicap principle
). (In 80% of cases this turns out to be true.) Vervet monkey
s' cries are among the most complex. Their utterances are effectively words: a vocabulary that defines each of their predators, so an alarm call
is specific to a particular threat. Some creatures transmit their presence by display, and Attenborough observes thousands of fireflies
illuminating the darkness. Sounds travel faster and further underwater, and over 200 species of fish use them to communicate. In turn, sea lion
s have become adept at sensing their proximity. However, the most visual aquatic animal is the squid
, which uses colour change
and posture to communicate. Finally, Attenborough swims with spotted dolphin
s. They converse with a series of ultrasonic
clicks, and each has a family call inherited from its mother: effectively a 'surname
'. They also use normal sound, body posture and touch — in short, in terms of ability to communicate, they are man
's closest rival.
inhabits long grass, and so is difficult to see. In order to gain attention, it 'trampolines' in the same spot for up to 400 times a day. Whale
s sing to their prospective partners, and the female's calls can be heard by suitors for over eight kilometres. When animals send out signals of attraction, they must also ensure that they don't entice the wrong species, and so have markings that differ prominently. Attenborough highlights the booby
as an example: there are around half a dozen species, all of which may occupy the same island. However, the blue-footed booby
reassures its chosen mate by continually lifting its feet. Tropicbird
s and marsh harrier
s are shown providing graceful aerobatic displays, while the sac-winged bat
uses a strong perfume to lure a companion. Among those birds that produce the most spectacular visual displays are the lyrebird
(which also has an elaborate song), the peacock
, and the riflebird (and indeed most other birds of paradise). The bowerbird
invites potential partners to inspect its bower: a specially prepared area that contains a hut or walkway augmented by strikingly coloured objects. The intricate dances performed by manakin
s in Trinidad
are also examined. Finally, Attenborough observes the topi
's display courts, whose sharply defined boundaries are jealously guarded by rival males.
s are passed on to the next generation. It is a universal problem, but one which has given rise to a variety of solutions. Barnacle
s cannot move, but each has both male
and female
sex cells, allowing each neighbour to be a potential mate. On the other end of the scale, a female elephant undergoes a long pregnancy
— 22 months — and so wishes to ensure that her calf is fathered by a strong and proven male. She is therefore very choosy about her partner. A female chinchilla
is even more so, and rejects an unwanted suitor by squirting urine
in its face. Mating is a dangerous business when weapons are involved, and a male tarantula
approaches his intended with trepidation. Only when he succeeds in holding off her poison
fangs is he able to progress any further. For some, the right moments to get together are few and far between: a male crab
, for example, must wait until a female moult
s her shell before he is able to fertilise her. Male sea lions are shown fighting over a harem
, and some use the battle to their advantage by making off with reluctant females. Attenborough observes that the monogamous
relationships enjoyed by humans are rare within the animal kingdom, but he highlights the Royal albatross
as a "beautiful" exception. The pair of birds featured met as five-year-olds, and have been together for twenty years.
. Erroneously entitled Trials of Life, its sole extra feature is a 50-minute documentary: The Making of The Trials of Life. It was previously released in 2002 as an abridged 3-disc set, with each episode cut to 35 minutes.
The accompanying book, The Trials of Life: A Natural History of Behaviour by David Attenborough (ISBN 0-00-219912-2), was published by BBC Books on 4 October 1990 and was shortlisted for the 1991 Rhône-Poulenc Prize. It is currently out of print.
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
nature documentary
Nature documentary
A natural history film or wildlife film is a documentary film about animals, plants, or other non-human living creatures, usually concentrating on film taken in their natural habitat...
series written and presented by David Attenborough
David Attenborough
Sir David Frederick Attenborough OM, CH, CVO, CBE, FRS, FZS, FSA is a British broadcaster and naturalist. His career as the face and voice of natural history programmes has endured for more than 50 years...
, first transmitted in the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
from 4 October 1990.
A study in animal behaviour, it was the third in a trilogy of major series (beginning with Life on Earth) that took a broad overview of nature, rather than the more specialised surveys of Attenborough's later productions. Each of the twelve 50-minute episodes features a different aspect of the journey through life, from birth to adulthood and continuation of the species through reproduction.
The series was produced in conjunction with the Australian Broadcasting Service
Australian Broadcasting Corporation
The Australian Broadcasting Corporation, commonly referred to as "the ABC" , is Australia's national public broadcaster...
and Turner Broadcasting System
Turner Broadcasting System
Turner Broadcasting System, Inc. is the Time Warner subsidiary managing the collection of cable networks and properties started and acquired by Robert Edward "Ted" Turner starting in the mid-1970s. The company has its headquarters in the CNN Center in Atlanta, Georgia. TBS, Inc...
Inc. The executive producer was Peter Jones and the music was composed by George Fenton
George Fenton
George Fenton is a British composer best known for his work writing film scores and music for television, although he also writes music for the theatre. His real name is George Howe but he is better known by his pseudonym of George Fenton.-Selected film and television credits:Fenton has composed...
.
Part of David Attenborough's 'Life' series, it was preceded by The Living Planet
The Living Planet
The Living Planet: A Portrait of the Earth is a BBC nature documentary series written and presented by David Attenborough, first transmitted in the UK from 19 January 1984....
(1984) and followed by Life in the Freezer
Life in the Freezer
Life in the Freezer is a BBC nature documentary series written and presented by David Attenborough, first transmitted in the UK from 18 November 1993....
(1993).
Background
The series took over three-and-a-half years to film, during which time Attenborough travelled almost a quarter of a million miles. The production team sought to further push the boundaries of natural history filmmaking, following on from the advances made in The Living Planet, and were provided with several new challenges.The sequence of chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s hunting colobus monkey
Western Red Colobus
The western red colobus is a species of Old World monkey found in West African forests from Senegal to Ghana. All other species of red colobuses have formerly been considered subspecies of P. badius. It is often hunted by the common chimpanzee...
s was only possible through the efforts of Hedwige and Christophe Boesch
Christophe Boesch
Christophe Boesch is a primatologist who studies chimpanzees. He and his wife work together, and he has both written articles and directed documentaries about chimpanzees....
, who had spent five years studying the apes in the Ivory Coast
Côte d'Ivoire
The Republic of Côte d'Ivoire or Ivory Coast is a country in West Africa. It has an area of , and borders the countries Liberia, Guinea, Mali, Burkina Faso and Ghana; its southern boundary is along the Gulf of Guinea. The country's population was 15,366,672 in 1998 and was estimated to be...
forests of West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
.
Meanwhile, a bivouac
Bivouac (ants)
A bivouac is a structure formed by migratory army ant and driver ant colonies, where a nest is constructed out of the living ant worker's own bodies to protect the queen and larvae, and is later deconstructed as the ants move on....
of army ant
Army ant
The name army ant is applied to over 200 ant species, in different lineages, due to their aggressive predatory foraging groups, known as "raids", in which huge numbers of ants forage simultaneously over a certain area, attacking prey en masse.Another shared feature is that, unlike most ant...
s in Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
was able to be filmed internally with the aid of a medical endoscope
Endoscopy
Endoscopy means looking inside and typically refers to looking inside the body for medical reasons using an endoscope , an instrument used to examine the interior of a hollow organ or cavity of the body. Unlike most other medical imaging devices, endoscopes are inserted directly into the organ...
. Furthermore, a new type of camera lens enabled tree ants to be filmed in enlarged close-up just in front of Attenborough — with both subjects in sharp focus. This gave the illusion that the insects were much larger than their actual size.
Filming critical moments in the life of a herd of elephant
Elephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...
s necessitated the expertise of Cynthia Moss
Cynthia Moss
Cynthia Moss is an American conservationist, wildlife researcher and writer, who specialises in elephant behaviour. She has published several books including Portraits in the Wild: Animal Behaviour in East Africa .-Life and work:Moss graduated at Smith College in Massachusetts in 1962, majoring in...
, who had devoted 25 years to researching the animals in Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
. She was able to advise the production team on the right moments to film specific events.
The camera team had only one chance to film a 60,000-strong flock of wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...
s flying over David Attenborough's head in Norfolk
Norfolk
Norfolk is a low-lying county in the East of England. It has borders with Lincolnshire to the west, Cambridgeshire to the west and southwest and Suffolk to the south. Its northern and eastern boundaries are the North Sea coast and to the north-west the county is bordered by The Wash. The county...
, and the RSPB
Royal Society for the Protection of Birds
Bird Notes and News was first published in April 1903.The title changed to 'Bird Notes' in 1947. In the 1950s, there were four copies per year . Each volume covered two years, spread over three calendar years...
was enlisted to predict their flightpath. By contrast, the Florida scrub jay
Florida Scrub Jay
The Florida Scrub-Jay is one of the species of scrub-jay native to North America. It is the only species of bird endemic to the U.S. state of Florida. Because of this, it is heavily sought by birders who travel from across the country to observe this unique species...
s couldn't have been more co-operative: since the particular group being filmed had been studied closely and were used to humans, a bird could land on Attenborough's hand right on cue.
The inside of a termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
mound proved especially challenging for Attenborough: it was so cramped that he could only face in one direction. He therefore had to slowly crawl backwards out of shot when performing re-takes.
Behaviour seen for the first time included the sequence that was eventually selected to illustrate the series' DVD cover: that of a killer whale
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
pouncing on a colony of sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
s on a Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
n beach and 'playing' with its young prey before consuming it. This meant some risks being taken by the cameramen, as they placed themselves in the water just feet away from the creatures in order to obtain close-ups of an attack run.
Episodes
1. "Arriving"
Christmas Island red crab
The Christmas Island red crab, Gecarcoidea natalis, is a species of land crab that is endemic to Christmas Island and the Cocos Islands in the Indian Ocean...
, of which there are estimated to be some 120 million. The exercise is all the more hazardous since the species is a land crab, and the eggs have to be deposited in the sea — where the most ancient animals on the planet still live and breed. One of the most prolific aquatic egg producers is the giant clam
Giant clam
The giant clam, Tridacna gigas , is the largest living bivalve mollusc. T. gigas is one of the most endangered clam species. It was mentioned as early as 1825 in scientific reports...
, but some land animals also lay vast quantities, and the mantis
Mantis
Mantis is the common name of any insect in the order Mantodea, also commonly known as praying mantises. The word itself means "prophet" in Latin and Greek...
is one example. In the Western United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, Attenborough observes a wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
that digs a burrow, conceals it, and stocks it with fresh caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
s for her emerging young. The grubs of another start life inside caterpillars, and eat the unsuspecting hosts
Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
. The problems of larger animals are illustrated by snow geese
Snow Goose
The Snow Goose , also known as the Blue Goose, is a North American species of goose. Its name derives from the typically white plumage. The genus of this bird is disputed...
in the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
, which have to defend their eggs from arctic fox
Arctic fox
The arctic fox , also known as the white fox, polar fox or snow fox, is a small fox native to Arctic regions of the Northern Hemisphere and is common throughout the Arctic tundra biome. The Greek word alopex, means a fox and Vulpes is the Latin version...
es. The process of embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
nic growth inside the egg, from laying to hatching, is shown in detail. The malleefowl
Malleefowl
The Malleefowl is a stocky ground-dwelling Australian bird about the size of a domestic chicken...
warms its eggs with rotting leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
, and Attenborough demonstrates the care with which it regulates them by adding sand to its mound — to have it kicked back in his face. The sea louse is a crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
that commits suicide: its grubs consume so much of the mother’s energies that she dies after birth. Mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s shown giving birth to fully formed young include wildebeest
Wildebeest
The wildebeest , also called the gnu is an antelope of the genus Connochaetes. It is a hooved mammal...
, antelope
Antelope
Antelope is a term referring to many even-toed ungulate species indigenous to various regions in Africa and Eurasia. Antelopes comprise a miscellaneous group within the family Bovidae, encompassing those old-world species that are neither cattle, sheep, buffalo, bison, nor goats...
, sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
s and chinchilla
Chinchilla
Chinchillas are crepuscular rodents, slightly larger and more robust than ground squirrels, and are native to the Andes mountains in South America. Along with their relatives, viscachas, they make up the family Chinchillidae....
s.
2. "Growing Up"
Broadcast 11 October 1990, this programme describes the ways that various species care for their young. Attenborough defines childhood as achieving two tasks: growing and surviving. He highlights the elephant sealElephant seal
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...
as an animal that experiences a compressed childhood, being abandoned after three weeks and left for up to another eight alone, while it becomes large enough to be able to swim. For tern
Tern
Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...
s, there is safety in numbers as the dense population works together to drive out marauding gull
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
s. The snow geese in the Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n Arctic show intense devotion as they escort their goslings by foot to the coast some 50 kilometres away. Scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s carry their young on their backs, while a shrew
Shrew
A shrew or shrew mouse is a small molelike mammal classified in the order Soricomorpha. True shrews are also not to be confused with West Indies shrews, treeshrews, otter shrews, or elephant shrews, which belong to different families or orders.Although its external appearance is generally that of...
will leave hers under a stone while she goes to feed. The eider duck
Common Eider
The Common Eider, Somateria mollissima, is a large sea-duck that is distributed over the northern coasts of Europe, North America and eastern Siberia. It breeds in Arctic and some northern temperate regions, but winters somewhat farther south in temperate zones, when it can form large flocks on...
is one creature that shares responsibility for its offspring: females regularly supervise the ducklings of others in a group. The mara
Mara (mammal)
The maras are a genus of the cavy family. They are the sole representatives of the subfamily Dolichotinae. These large relatives of guinea pigs are common in the Patagonian steppes of Argentina but live in other areas of South America as well such as Paraguay...
is another that uses a crèche
Crèche (zoology)
The Crèche in zoology refers to care of another's offspring, for instance in a colony. This term is used in the study of bird colonies...
system, as does the bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
, whose nurseries can be up to a million strong. The Florida scrub jay has a complex system of raising young known as cooperative breeding
Cooperative breeding
Cooperative breeding is a social system in which individuals contribute care to offspring that are not their own at the expense of their own reproduction . When reproduction is monopolized by one or few of the adult group members and most adults do not reproduce, but help rear the breeder’s...
, where young stay on as helpers at the nest of their parents. Such behaviour is exhibited on a larger scale by elephants, where all females take an interest in raising a single calf. A chimpanzee’s childhood is socially complicated, as an individual must learn how to behave towards others, as well as master the use of tools. Albatross
Albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
es must be accomplished fliers as soon as possible — chicks are shown being hunted by tiger shark
Tiger shark
The tiger sharks, Galeocerdo cuvier, is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as sea tigers, tiger sharks are relatively large macropredators, capable of attaining a length of over . It is found in many tropical and temperate waters, and is...
s.
3. "Finding Food"
Broadcast 18 October 1990, the next instalment is devoted to the ways in which animals gather their sustenance. Attenborough begins in the South AmericaSouth America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n rainforest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
, where the proliferation of animal and plant life does not necessarily make it easy to find food. Some leaves are poisonous, and so those that eat them have to be careful. Other plants use food (or nectar) as a bribe to get their pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
transported, and several species of hummingbird
Hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...
have developed exclusive relationships with certain of them. Fruit is also on offer, again as a means of reproduction, and creatures such as squirrel monkey
Squirrel monkey
The squirrel monkeys are the New World monkeys of the genus Saimiri. They are the only genus in the subfamily Saimirinae.Squirrel monkeys live in the tropical forests of Central and South America in the canopy layer. Most species have parapatric or allopatric ranges in the Amazon, while S...
s eat little else. Meanwhile, parrot
Parrot
Parrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae , the Cacatuidae and the Strigopidae...
s and macaw
Macaw
Macaws are small to large, often colourful New World parrots. Of the many different Psittacidae genera, six are classified as macaws: Ara, Anodorhynchus, Cyanopsitta, Primolius, Orthopsittaca, and Diopsittaca...
s take kaolin
Kaolinite
Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra...
as an antidote to their diet of toxic seeds. Attenborough witnesses a 60,000 strong flock of knot
Red Knot
The Red Knot, Calidris canutus , is a medium sized shorebird which breeds in tundra and the Arctic Cordillera in the far north of Canada, Europe, and Russia. It is a large member of the Calidris sandpipers, second only to the Great Knot...
and dunlin
Dunlin
The Dunlin, Calidris alpina, is a small wader, sometimes separated with the other "stints" in Erolia. It is a circumpolar breeder in Arctic or subarctic regions. Birds that breed in northern Europe and Asia are long-distance migrants, wintering south to Africa, southeast Asia and the Middle East...
suddenly take advantage of a low tide to feed on tiny mud-dwelling molluscs. Barracuda
Barracuda
The barracuda is a ray-finned fish known for its large size and fearsome appearance. Its body is long, fairly compressed, and covered with small, smooth scales. Some species could reach up to 1.8m in length and 30 cm in width...
hunt small fish, and drive shoals of them into bays to be eaten by pelican
Pelican
A pelican, derived from the Greek word πελεκυς pelekys is a large water bird with a large throat pouch, belonging to the bird family Pelecanidae....
s, which are besieged by gulls that attempt to steal their catches. One species of gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
is able to differentiate between worker termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s and the more dangerous soldiers. The web of the orb spider
Orb-weaver spider
The "typical" orb-weaver spiders are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields and forests...
is hailed as one of the most elegant food catching devices, and the methods of two others, nephila
Golden silk orb-weaver
The golden silk orb-weavers are a genus of araneomorph spiders noted for the impressive webs they weave. Nephila consists of numerous individual species found around the world. They are also commonly called golden orb-weavers, giant wood spiders, or banana spiders...
and its kleptoparasite
Kleptoparasitism
Kleptoparasitism or cleptoparasitism is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food...
visitor, argyrodes
Argyrodes
Spiders of the genus Argyrodes , also called dewdrop spiders, occur worldwide. They are best known as kleptoparasites: they steal other spiders' prey. They invade and reside in their host's web even though they can spin their own webs...
, are explored in detail. Finally, tropicbirds, their crop
Crop (anatomy)
A crop is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion that is found in many animals, including gastropods, earthworms, leeches, insects, birds, and even some dinosaurs.- Bees :Cropping is used by bees to temporarily store nectar of flowers...
s full with food en route back to their nests, are ambushed in mid-air by a group of frigatebird
Frigatebird
The frigatebirds are a family, Fregatidae, of seabirds. There are five species in the single genus Fregata. They are also sometimes called Man of War birds or Pirate birds. Since they are related to the pelicans, the term "frigate pelican" is also a name applied to them...
s, whose aim is to make them surrender their cargo.
4. "Hunting and Escaping"
Skua
The skuas are a group of seabirds with about seven species forming the family Stercorariidae and the genus Stercorarius. The three smaller skuas are called jaegers in North America....
s as he approaches their nest, which demonstrates this particular bird's aggressive behaviour, both when taking food and defending its young. Off the shores of Patagonia, the same group of killer whales returns each year to ambush sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
pups, which stray out of the safer shallow waters. Having grabbed their prey, they take it back out to sea and 'play
Play (activity)
Play is a term employed in ethology and psychology to describe to a range of voluntary, intrinsically motivated activities normally associated with pleasure and enjoyment...
' with it for some time before killing it. Poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....
can be used both as a weapon and a deterrent, such as by the viper
Viperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
and tomato frog
Tomato frog
The 'Tomato frog' is any one of the three species of genus Dyscophus : D. antongilii, D. insularis, or D. guineti.The tomato frog originally came from Madagascar. The common name comes from the frog's bright red color. When threatened, a tomato frog puffs up its body...
respectively. Some animals advertise their defensive measures in advance, in case deployment occurs too late. Among them are the skunk
Skunk
Skunks are mammals best known for their ability to secrete a liquid with a strong, foul odor. General appearance varies from species to species, from black-and-white to brown or cream colored. Skunks belong to the family Mephitidae and to the order Carnivora...
, which discharges an appalling smell, and some salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
s that display their toxicity by remaining stationary, with their warning markings
Aposematism
Aposematism , perhaps most commonly known in the context of warning colouration, describes a family of antipredator adaptations where a warning signal is associated with the unprofitability of a prey item to potential predators...
visible. Several species of stick insect
Phasmatodea
The Phasmatodea are an order of insects, whose members are variously known as stick insects , walking sticks or stick-bugs , phasmids, ghost insects and leaf insects...
and their elaborate camouflage are shown. However, none of these methods of protection pose problems to army ant
Army ant
The name army ant is applied to over 200 ant species, in different lineages, due to their aggressive predatory foraging groups, known as "raids", in which huge numbers of ants forage simultaneously over a certain area, attacking prey en masse.Another shared feature is that, unlike most ant...
s, which can subdue any of their prey, simply by virtue of their size and vast numbers. The Harris hawk
Harris's Hawk
The Harris's Hawk or Harris Hawk formerly known as the Bay-winged Hawk or Dusky Hawk, is a medium-large bird of prey which breeds from the southwestern United States south to Chile and central Argentina...
is unusual, since it hunts in teams, and a group of six are shown practising their skill in the desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
of New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. The final sequence depicts a troop of chimpanzee
Common Chimpanzee
The common chimpanzee , also known as the robust chimpanzee, is a great ape. Colloquially, the common chimpanzee is often called the chimpanzee , though technically this term refers to both species in the genus Pan: the common chimpanzee and the closely related bonobo, formerly called the pygmy...
s displaying strategy and co-ordination as it successfully pursues colobus monkeys through a forest in the Ivory Coast.
5. "Finding the Way"
Broadcast 1 November 1990, this programme explores forms of navigation. Attenborough starts in AfricaAfrica
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
at dusk, by describing some of the species that don't rely on sight
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
. The spotted hyena
Spotted Hyena
The spotted hyena also known as laughing hyena, is a carnivorous mammal of the family Hyaenidae, of which it is the largest extant member. Though the species' prehistoric range included Eurasia extending from Atlantic Europe to China, it now only occurs in all of Africa south of the Sahara save...
uses its acute sense of smell
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
to guide it while it hunts nocturnally, while galago
Galago
Galagos , also known as bushbabies, bush babies or nagapies , are small, nocturnal primates native to continental Africa, and make up the family Galagidae...
s urinate on their hands so they can completely mark their movements. Some animals use echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
and these include swiftlet
Swiftlet
Swiftlets are birds contained within the four genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia. They form the Collocaliini tribe within the swift family Apodidae. The group contains around thirty species mostly confined to southern Asia, south Pacific islands, and northeastern...
s, bats and river dolphin
River dolphin
River dolphins are the four living species of dolphin that reside in freshwater rivers and estuaries. River dolphins inhabit areas of Asia and South America. They are classed in the Platanistoidea superfamily of cetaceans. Three species live in fresh water rivers. The fourth species, the La Plata...
s. By contrast, electric eel
Electric eel
The electric eel , is an electric fish, and the only species of the genus Electrophorus. It is capable of generating powerful electric shocks, of up to six hundred volts, which it uses for both hunting and self-defense. It is an apex predator in its South American range...
s use fields of electricity to sense their environment. During the hours of daylight, other methods are employed: the rufous elephant shrew
Elephant shrew
Elephant shrews or jumping shrews are small insectivorous mammals native to Africa, belonging to the family Macroscelididae, in the order Macroscelidea...
, with its carefully cleared network of pathways, has a sharp mental picture of its habitat — even knowing the various shortcuts with which to evade capture. Attenborough visits the Sahara
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...
to illustrate a species that makes the longest overland journey of any insect: cataglyphis
Sahara desert ant
The Sahara Desert ant is a desert-dwelling ant of the genus Cataglyphis. It inhabits the Sahara Desert and is one of the most heat tolerant animals known to date. However, there are at least four other species of Cataglyphis living in the Sahara desert, for example C. bombycina, C. savigny, C....
, an ant that uses the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
's position to enable it to return to its nest in a straight line. Lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
s in the Bahamas
The Bahamas
The Bahamas , officially the Commonwealth of the Bahamas, is a nation consisting of 29 islands, 661 cays, and 2,387 islets . It is located in the Atlantic Ocean north of Cuba and Hispaniola , northwest of the Turks and Caicos Islands, and southeast of the United States...
are shown marching in columns to escape stormy waters. In its search for perpetual daylight in which to fish, the Arctic tern
Arctic Tern
The Arctic Tern is a seabird of the tern family Sternidae. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe, Asia, and North America...
makes a 19,000-kilometre journey from one end of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
to the other. The albatross
Albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
is highlighted as one of the most skilled navigators: it can travel up to 1300 kilometres over sea in search of food for its chicks, and still find its way back to the nest. Finally, Attenborough stands on a waterfall in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
to tell of the three-year, 10,000-kilometre journey made by elver
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...
s.
6. "Home Making"
Broadcast 8 November 1990, this instalment deals with how animals construct their shelters from the elements and predators. Burrows and holes can provide considerable refuge, and Attenborough inspects the home of the American prairie dogPrairie dog
Prairie dogs are burrowing rodents native to the grasslands of North America. There are five different species of prairie dogs: black-tailed, white-tailed, Gunnison's, Utah and Mexican prairie dogs. They are a type of ground squirrel, found in the United States, Canada and Mexico...
, an elaborate construction that has its own air conditioning system. Silk
Silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...
is such a valuable commodity that those that can't make it steal it instead. The hermit hummingbird
Hermit (hummingbird)
The hermits are tropical and subtropical hummingbirds in the subfamily Phaethornithinae, comprising 30–40 species in six genera. They occur from southern Mexico, through Central America, to South America as far south as northern Argentina....
uses it to attach its nest to the underside of a leaf, while the Indian tailorbird
Tailorbird
Tailorbirds are small birds belonging to the genus Orthotomus often placed in the Old World warbler family Sylviidae. However, recent research suggests they more likely belong in the Cisticolidae and they are treated as such in Del Hoyo et al....
stitches two leaves together. However, the expert in complex nest-building is the weaverbird which makes its abode from over 1,000 strips of grass that are perfectly interwoven — and dismantling it if it fails to attract a mate. The beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
is responsible for one of the biggest animal dwellings: its wooden lodge that rises from the river bed stays in place from one generation to the next, and so requires constant maintenance. Some stingless bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
s use their wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...
and the resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
of tree bark to create labyrinthine structures containing various compartments. Mud
Mud
Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone . When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds...
is also used by several creatures, such as the potter wasp
Potter wasp
Potter wasps are a cosmopolitan wasp group presently treated as a subfamily of Vespidae, but sometimes recognized in the past as a separate family, Eumenidae.-Recognition:...
and the cliff swallow
Cliff Swallow
The Cliff Swallow is a member of the passerine bird family Hirundinidae — the swallows and martins.It breeds in North America, and is migratory, wintering in western South America from Venezuela southwards to northeast Argentina...
. The termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s' intricate creations allow for security, heating, air conditioning, self-contained nurseries and gardens, and sanitation systems. Attenborough hails the species as the consummate home maker, and explores a 15-foot colony in West Africa that contains 1.5 million insects: he crawls right inside to examine its method of ventilation.
7. "Living Together"
Chital
The chital or cheetal , also known as chital deer, spotted deer or axis deer is a deer which commonly inhabits wooded regions of Sri Lanka, Nepal, Bangladesh, Bhutan, India, and in small numbers in Pakistan...
follow langur monkey
Gray langur
Gray langurs or Hanuman langurs, the most widespread langurs of South Asia, are a group of Old World monkeys constituting the entirety of the genus Semnopithecus. All taxa have traditionally been placed in the single species Semnopithecus entellus...
s as they travel from tree to tree, eating any leaves that get dropped from above. In return, the deer serve as a lookout when the primates are feeding on the ground. Underwater, a hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...
is shown adding sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
s to its shell in order to protect itself from attack by an octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
, and a goby
Goby
The gobies form the family Gobiidae, which is one of the largest families of fish, with more than 2,000 species in more than 200 genera. Most are relatively small, typically less than 10 cm in length...
assists a virtually blind shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
. Flea
Flea
Flea is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood...
s, lice
Louse
Lice is the common name for over 3,000 species of wingless insects of the order Phthiraptera; three of which are classified as human disease agents...
and mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
s are parasites
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
: they share no mutual partnership and instead take advantage of creatures for food or shelter. However, parasites have their predators, and an example are the finch
Finch
The true finches are passerine birds in the family Fringillidae. They are predominantly seed-eating songbirds. Most are native to the Northern Hemisphere, but one subfamily is endemic to the Neotropics, one to the Hawaiian Islands, and one subfamily – monotypic at genus level – is found...
es of the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
that clear the resident giant tortoise
Giant tortoise
Giant tortoises are characteristic reptiles of certain tropical islands. Often reaching enormous size—they can weigh as much as 300 kg and can grow to be 1.3 m long—they live, or lived , in the Seychelles, the Mascarenes and the Galapagos...
s of their tick
Tick
Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...
s, and oxpecker
Oxpecker
The oxpeckers are two species of bird which make up the family Buphagidae. Some ornithologists regard them as a subfamily Buphaginae within the starling family Sturnidae but they appear to be quite distinct. Oxpeckers are endemic to the savanna of Sub-Saharan Africa...
s, which do the same for giraffe
Giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...
s in Africa (and even use its fur to line their nests). Some fish regularly clean others, and wrasse
Wrasse
The wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 82 genera, which are divided into nine subgroups or tribes....
and shrimp appear to specialise in this regard, as do remora
Remora
The remora , sometimes called a suckerfish or sharksucker, is an elongated, brown fish in the order Perciformes and family Echeneidae...
, which permanently hang on to their hosts. One parasite that grows inside its host is the fluke
Trematoda
Trematoda is a class within the phylum Platyhelminthes that contains two groups of parasitic flatworms, commonly referred to as "flukes".-Taxonomy and biodiversity:...
, and one is shown gestating inside a snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
, having previously been unknowingly eaten. Because it needs to transfer to a bird's gut to develop further, it causes the snail to advertise its presence to allow itself to be consumed — thus completing the circle. However, some microscopic creatures inhabit the stomachs of large herbivores in order to break down the cellulose of their diet, thereby aiding their digestion.
8. "Fighting"
Broadcast 22 November 1990, this programme details how fighting — both physical and psychological — is used for food, land or to gain a mate. Territorial conflict is demonstrated by the hummingbird, and Attenborough illustrates its aggressivenessAggression
In psychology, as well as other social and behavioral sciences, aggression refers to behavior between members of the same species that is intended to cause humiliation, pain, or harm. Ferguson and Beaver defined aggressive behavior as "Behavior which is intended to increase the social dominance of...
by placing a stuffed specimen nearby, only to have it speared by its opponent's bill. The midas cichlid
Cichlid
Cichlids are fishes from the family Cichlidae in the order Perciformes. Cichlids are members of a group known as the Labroidei along with the wrasses , damselfish , and surfperches . This family is both large and diverse. At least 1,300 species have been scientifically described, making it one of...
on the other hand, has no weapons to speak of, and so uses its mouth to hold on for trials of strength. By contrast, the forelegs of a mantis shrimp
Mantis shrimp
Mantis shrimp or stomatopods are marine crustaceans, the members of the order Stomatopoda. They are neither shrimp nor mantids, but receive their name purely from the physical resemblance to both the terrestrial praying mantis and the shrimp. They may reach in length, although exceptional cases of...
are powerful enough to crack the shell of another crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
: therefore disputes or courtship are fraught with danger. Animals that possess lethal food-gathering weapons usually don't use them against one another, as neither side wishes to risk death. For example, one venomous snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
will aim to floor the other, rather than bite. Wolves and big cat
Big cat
The term big cat – which is not a biological classification – is used informally to distinguish the larger felid species from smaller ones. One definition of "big cat" includes the four members of the genus Panthera: the tiger, lion, jaguar, and leopard. Members of this genus are the only cats able...
s largely use snarls and body posture to convey their threat. There are no holds barred between rival zebra
Zebra
Zebras are several species of African equids united by their distinctive black and white stripes. Their stripes come in different patterns unique to each individual. They are generally social animals that live in small harems to large herds...
s: kicking and biting is employed until a victor emerges, whereas giraffes slam their necks against each other. Normally peaceful mountain gorilla
Mountain Gorilla
The Mountain Gorilla is one of the two subspecies of the Eastern Gorilla. There are two populations. One is found in the Virunga volcanic mountains of Central Africa, within three National Parks: Mgahinga, in south-west Uganda; Volcanoes, in north-west Rwanda; and Virunga in the eastern Democratic...
s are shown squabbling when play gets out of hand, and one of them communicates real fright by urinating uncontrollably. Large herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s that have horns or antler
Antler
Antlers are the usually large, branching bony appendages on the heads of most deer species.-Etymology:Antler originally meant the lowest tine, the "brow tine"...
s are naturally inclined to use them to assert their dominance over the females in a herd. Duelling male ibex and Alaskan bull moose
Moose
The moose or Eurasian elk is the largest extant species in the deer family. Moose are distinguished by the palmate antlers of the males; other members of the family have antlers with a dendritic configuration...
undergo some of the most ferocious engagements — sometimes to the death.
9. "Friends and Rivals"
Broadcast 29 November 1990, this instalment investigates the ways in which those animals that live in social groups interact with each other. The solitary eagleEagle
Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...
is contrasted with whooper swan
Whooper Swan
The Whooper Swan , Cygnus cygnus, is a large Northern Hemisphere swan. It is the Eurasian counterpart of the North American Trumpeter Swan. An old name for the Whooper Swan is Elk; it is so called in Francis Willughby and John Ray's Ornithology of 1676.-Description:The Whooper Swan is similar in...
s landing in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
after a 1,600-kilometre journey from Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
. Once arrived, they must battle for territory with those already there, and pairs or families are usually victorious. Attenborough uses a group of farmyard chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
s to demonstrate a pecking order
Pecking order
Pecking order or just peck order is the colloquial term for a hierarchical system of social organization in chickens. It was first described from the behaviour of poultry by Thorleif Schjelderup-Ebbe in 1921 under the German terms Hackordnung or Hackliste' ...
. Caciques
Cacique (bird)
The caciques are passerine birds in the New World blackbird family. Members of the family are resident breeders in tropical South America and north to Mexico. All of the group are in the genus Cacicus, except the aberrant Yellow-billed Cacique , which constitutes a monotypic genus...
are shown cooperating to deter predators, despite their fighta amongst themselves to establish a pecking order. A pride of lion
Lion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...
s is shown co-operating to subdue a buffalo
African Buffalo
The African buffalo, affalo, nyati, Mbogo or Cape buffalo is a large African bovine. It is not closely related to the slightly larger wild Asian water buffalo, but its ancestry remains unclear...
. Afterwards, each animal peacefully awaits its turn at the carcass. Baboon
Baboon
Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominoid members of the primate order; only the mandrill and the drill are larger...
s live in troops of up to 150, and their complex dominance hierarchy
Dominance hierarchy
A dominance hierarchy is the organization of individuals in a group that occurs when competition for resources leads to aggression...
is examined in detail. Vampire bat
Vampire bat
Vampire bats are bats whose food source is blood, a dietary trait called hematophagy. There are three bat species that feed solely on blood: the Common Vampire Bat , the Hairy-legged Vampire Bat , and the White-winged Vampire Bat .All three species are native to the Americas, ranging from Mexico to...
s display reciprocal altruism
Reciprocal altruism
In evolutionary biology, reciprocal altruism is a behaviour whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, with the expectation that the other organism will act in a similar manner at a later time...
by regurgitating blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
for any neighbour that has missed out on a night's feeding. Dwarf mongoose
Mongoose
Mongoose are a family of 33 living species of small carnivorans from southern Eurasia and mainland Africa. Four additional species from Madagascar in the subfamily Galidiinae, which were previously classified in this family, are also referred to as "mongooses" or "mongoose-like"...
s live in family groups of around a dozen. While some look for food or sleep, others are always posted on the lookout for predators and quickly raise the alarm if necessary. Meanwhile, some of the most extreme co-operation is demonstrated by the underground naked mole rat
Naked Mole Rat
The naked mole rat , also known as the sand puppy or desert mole rat, is a burrowing rodent native to parts of East Africa and the only species currently classified in the genus Heterocephalus...
, whose 80-strong clusters are divided into workers (who tunnel perpetually), soldiers (who only act when danger threatens), and a single queen for breeding. Leafcutter ant
Leafcutter ant
Leafcutter ants, a non-generic name, are any of 47 species of leaf-chewing ants belonging to the two genera Atta and Acromyrmex.These species of tropical, fungus-growing ants are all endemic to South, Central America, Mexico and parts of the southern United States.The Acromyrmex and Atta ants have...
s are shown transporting their food deep below ground: it has to be planted in a special fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
to convert its indigestible cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
into something edible, and each stage of the operation is carried out by a different caste
Eusociality
Eusociality is a term used for the highest level of social organization in a hierarchical classification....
of individuals.
10. "Talking to Strangers"
Animal communication
Animal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...
. In Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
, Attenborough accompanies a tribesman who calls to a honeyguide
Honeyguide
Honeyguides are near passerine bird species of the order Piciformes. They are also known as indicator birds, or honey birds, although the latter term is also used more narrowly to refer to species of the genus Prodotiscus. They have an Old World tropical distribution, with the greatest number of...
, which in turn answers him and leads the pair to a bees' nest. The tribesman extracts the honey
Honey
Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...
, and some is left to reward the bird. African hunting dog
African Wild Dog
Lycaon pictus is a large canid found only in Africa, especially in savannas and lightly wooded areas. It is variously called the African wild dog, African hunting dog, Cape hunting dog, painted dog, painted wolf, painted hunting dog, spotted dog, or ornate wolf...
s are shown hunting gazelle
Gazelle
A gazelle is any of many antelope species in the genus Gazella, or formerly considered to belong to it. Six species are included in two genera, Eudorcas and Nanger, which were formerly considered subgenera...
s, of which the target is the individual that leaps
Stotting
Stotting is a gait of quadrupeds, particularly gazelles , involving jumping high into the air by lifting all four feet off the ground simultaneously. This may occur during pursuit by a predator...
lowest. Lark
Lark
Larks are passerine birds of the family Alaudidae. All species occur in the Old World, and in northern and eastern Australia; only one, the Shore Lark, has spread to North America, where it is called the Horned Lark...
s evade merlin
Merlin (bird)
The Merlin is a small species of falcon from the Northern Hemisphere. A bird of prey once known colloquially as a pigeon hawk in North America, the Merlin breeds in the northern Holarctic; some migrate to subtropical and northern tropical regions in winter.-European and North American...
by sending a similar message: by continuing to sing while being chased, it tells the pursuer that its prey is fit and therefore will be difficult to catch (see handicap principle
Handicap principle
The handicap principle is a hypothesis originally proposed in 1975 by biologist Amotz Zahavi to explain how evolution may lead to "honest" or reliable signaling between animals who have an obvious motivation to bluff or deceive each other...
). (In 80% of cases this turns out to be true.) Vervet monkey
Chlorocebus
Chlorocebus is a genus of medium-sized primates from the family of Old World monkeys. There are six species currently recognized, although some classify them all as a single species with numerous subspecies...
s' cries are among the most complex. Their utterances are effectively words: a vocabulary that defines each of their predators, so an alarm call
Alarm call
In the field of animal communication, an alarm signal is an antipredator adaptation referring to various signals emitted by social animals in response to danger. Many primates and birds have elaborate alarm calls for warning conspecifics of approaching predators. For example, the characteristic...
is specific to a particular threat. Some creatures transmit their presence by display, and Attenborough observes thousands of fireflies
Firefly
Lampyridae is a family of insects in the beetle order Coleoptera. They are winged beetles, and commonly called fireflies or lightning bugs for their conspicuous crepuscular use of bioluminescence to attract mates or prey. Fireflies produce a "cold light", with no infrared or ultraviolet frequencies...
illuminating the darkness. Sounds travel faster and further underwater, and over 200 species of fish use them to communicate. In turn, sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
s have become adept at sensing their proximity. However, the most visual aquatic animal is the squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
, which uses colour change
Chromatophore
Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development...
and posture to communicate. Finally, Attenborough swims with spotted dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s. They converse with a series of ultrasonic
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
clicks, and each has a family call inherited from its mother: effectively a 'surname
Surname
A surname is a name added to a given name and is part of a personal name. In many cases, a surname is a family name. Many dictionaries define "surname" as a synonym of "family name"...
'. They also use normal sound, body posture and touch — in short, in terms of ability to communicate, they are man
Human
Humans are the only living species in the Homo genus...
's closest rival.
11. "Courting"
Broadcast 13 December 1990, this programme surveys the methods employed in attracting a mate, mainly those of birds. The Indian floricanLesser Florican
The Lesser Florican , also known as the Likh, is a large bird in the bustard family and the only member of the genus Sypheotides. It is endemic to the Indian Subcontinent where it is found in tall grasslands and is best known for the leaping breeding displays made by the males during the Monsoon...
inhabits long grass, and so is difficult to see. In order to gain attention, it 'trampolines' in the same spot for up to 400 times a day. Whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s sing to their prospective partners, and the female's calls can be heard by suitors for over eight kilometres. When animals send out signals of attraction, they must also ensure that they don't entice the wrong species, and so have markings that differ prominently. Attenborough highlights the booby
Booby
A booby is a seabird in the genus Sula, part of the Sulidae family. Boobies are closely related to the gannets , which were formerly included in Sula.-Description:...
as an example: there are around half a dozen species, all of which may occupy the same island. However, the blue-footed booby
Blue-footed Booby
The Blue-footed Booby is a bird in the Sulidae family which comprises ten species of long-winged seabirds. The natural breeding habitat of the Blue-footed Booby is tropical and subtropical islands off the Pacific Ocean, most famously, the Galápagos Islands, Ecuador.- Etymology :The name booby...
reassures its chosen mate by continually lifting its feet. Tropicbird
Tropicbird
Tropicbirds are a family, Phaethontidae, of tropical pelagic seabirds now classified in their own order Phaethontiformes. Their relationship to other living birds is unclear, and they appear to have no close relatives. There are three species in one genus, Phaethon...
s and marsh harrier
Marsh harrier
The marsh harriers are birds of prey of the harrier subfamily. They are medium-sized raptors and the largest and broadest-winged harriers. Most of them are associated with marshland and dense reedbeds...
s are shown providing graceful aerobatic displays, while the sac-winged bat
Sac-winged bat
The 51 species of sac-winged or sheath-tailed bats constitute the family Emballonuridae, and can be found in tropical and subtropical regions all over the world. Emballonurids include some of the smallest of all bats, and range from 3.5 to 10 cm in body length...
uses a strong perfume to lure a companion. Among those birds that produce the most spectacular visual displays are the lyrebird
Lyrebird
A Lyrebird is either of two species of ground-dwelling Australian birds, that form the genus, Menura, and the family Menuridae. They are most notable for their superb ability to mimic natural and artificial sounds from their environment. Lyrebirds have unique plumes of neutral coloured...
(which also has an elaborate song), the peacock
Peafowl
Peafowl are two Asiatic species of flying birds in the genus Pavo of the pheasant family, Phasianidae, best known for the male's extravagant eye-spotted tail, which it displays as part of courtship. The male is called a peacock, the female a peahen, and the offspring peachicks. The adult female...
, and the riflebird (and indeed most other birds of paradise). The bowerbird
Bowerbird
Bowerbirds make up the bird family Ptilonorhynchidae. The family has 20 species in eight genera. These are medium-sized passerines, ranging from the Golden Bowerbird to the Great Bowerbird...
invites potential partners to inspect its bower: a specially prepared area that contains a hut or walkway augmented by strikingly coloured objects. The intricate dances performed by manakin
Manakin
The manakins are a family, Pipridae, of unique small suboscine passerine birds. The family contains some 60 species. They are distributed through the American tropics...
s in Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...
are also examined. Finally, Attenborough observes the topi
Topi
The Tsessebe , is one of five subspecies in the binomial class D. lunatus. The other subspecies include Korrigum , Tiang , Coastal Topi , and Topi . Tesessebe are found primarily in Zambia, Namibia, Botswana, Zimbabwe, and South Africa...
's display courts, whose sharply defined boundaries are jealously guarded by rival males.
12. "Continuing the Line"
Broadcast 20 December 1990, the final instalment illustrates how species fulfil their ultimate raison d'être and ensure that their geneGene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s are passed on to the next generation. It is a universal problem, but one which has given rise to a variety of solutions. Barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s cannot move, but each has both male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
and female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
sex cells, allowing each neighbour to be a potential mate. On the other end of the scale, a female elephant undergoes a long pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
— 22 months — and so wishes to ensure that her calf is fathered by a strong and proven male. She is therefore very choosy about her partner. A female chinchilla
Chinchilla
Chinchillas are crepuscular rodents, slightly larger and more robust than ground squirrels, and are native to the Andes mountains in South America. Along with their relatives, viscachas, they make up the family Chinchillidae....
is even more so, and rejects an unwanted suitor by squirting urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
in its face. Mating is a dangerous business when weapons are involved, and a male tarantula
Tarantula
Tarantulas comprise a group of often hairy and often very large arachnids belonging to the family Theraphosidae, of which approximately 900 species have been identified. Some members of the same Suborder may also be called "tarantulas" in the common parlance. This article will restrict itself to...
approaches his intended with trepidation. Only when he succeeds in holding off her poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....
fangs is he able to progress any further. For some, the right moments to get together are few and far between: a male crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
, for example, must wait until a female moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
s her shell before he is able to fertilise her. Male sea lions are shown fighting over a harem
Polygyny
Polygyny is a form of marriage in which a man has two or more wives at the same time. In countries where the practice is illegal, the man is referred to as a bigamist or a polygamist...
, and some use the battle to their advantage by making off with reluctant females. Attenborough observes that the monogamous
Monogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
relationships enjoyed by humans are rare within the animal kingdom, but he highlights the Royal albatross
Southern Royal Albatross
The Southern Royal Albatross, Diomedea epomophora, is a large seabird from the albatross family. At an average wingspan of around , it is the second largest albatross, behind the Wandering Albatross.-Taxonomy:...
as a "beautiful" exception. The pair of birds featured met as five-year-olds, and have been together for twenty years.
DVD and book
The series is available in the UK for Regions 2 and 4 as a 4-disc DVD set (BBCDVD1428, released 27 September 2004) and as part of The Life CollectionThe Life Collection
The Life Collection is a 24-disc DVD box set of eight titles from David Attenborough's 'Life' series of BBC natural history programmes. It was released in the UK on 5 December 2005 and has also been made available on Region 4 DVD in Australia and New Zealand. The Region 4 DVD contains four fewer...
. Erroneously entitled Trials of Life, its sole extra feature is a 50-minute documentary: The Making of The Trials of Life. It was previously released in 2002 as an abridged 3-disc set, with each episode cut to 35 minutes.
The accompanying book, The Trials of Life: A Natural History of Behaviour by David Attenborough (ISBN 0-00-219912-2), was published by BBC Books on 4 October 1990 and was shortlisted for the 1991 Rhône-Poulenc Prize. It is currently out of print.