Whitetip reef shark
Encyclopedia
The whitetip reef shark (Triaenodon obesus) is a species
of requiem shark
, family
Carcharhinidae, and the only member of its genus
. A small shark usually not exceeding 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostril
s, oval eyes with vertical pupils, and white-tipped dorsal
and caudal fins. One of the most common sharks found on Indo-Pacific
coral reef
s, the whitetip reef shark occurs as far west as South Africa
and as far east as Central America
. It is typically found on or near the bottom in clear water, at a depth of 8 metre.
During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gill
s and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, crustacean
s, and octopus
in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individual whitetip reef sharks may stay within a particular area of the reef for months to years, time and again returning to the same shelter. This species is viviparous, in which the developing embryo
s sustained by a placenta
l connection to their mother. One of the few sharks in which mating
has been observed in the wild, receptive female whitetip reef sharks are followed by prospective males, who attempt to grasp her pectoral fin and maneuver the two of them into positions suitable for copulation. Females give birth to 1–6 pups every other year, after a gestation period
of 10–13 months.
Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though there are reports of ciguatera poisoning resulting from its consumption. The International Union for Conservation of Nature (IUCN) has assessed the whitetip reef shark as Near Threatened
, noting that its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to over-exploitation
.
as Carcharias obesus, in the 1837 Fische des Rothen Meeres (Fishes of the Red Sea). His choice of the specific epithet obesus was curious, given that this shark is actually quite slender. Later in 1837, Johannes Müller
and Friedrich Henle
moved this species into its own genus Triaenodon, from the Greek
triaena meaning "trident", and odon meaning "tooth". As Rüppell did not originally designate a holotype
, in 1960 a 31 cm (12.2 in) long specimen caught off Jeddah
, Saudi Arabia
was made the species lectotype
. Other common name
s for this shark include blunthead shark, light-tip shark, reef whitetip shark, and whitetip shark.
Once placed in the family Triakidae, the whitetip reef shark is now recognized by most authors as belonging to the family Carcharhinidae on the basis of morphological
characters such as a full nictitating membrane
, well-developed precaudal pit, strong lower caudal fin lobe, and scroll-like intestinal
valves. Morphological and molecular phylogenetic analyses suggest that the whitetip reef shark is grouped with the lemon sharks
(Negaprion) and the sliteye shark
(Loxodon) in occupying an intermediate position on the carcharhinid evolutionary tree, between most basal
genera (Galeocerdo, Rhizoprionodon
, and Scoliodon) and the most derived
(Carcharhinus
and Sphyrna
).
region. In the Indian Ocean, it occurs from northern KwaZulu-Natal
, South Africa
to the Red Sea
and the Indian subcontinent
, including Madagascar
, Mauritius
, the Comoros
, the Aldabra Group
, the Seychelles
, Sri Lanka
, and the Chagos Archipelago
. In the western and central Pacific, it is occurs from off southern China
, Taiwan
, and the Ryukyu Islands
, to the Philippines
, Southeast Asia
, and Indonesia
, to northern Australia
, and is also found around numerous islands in Melanesia
, Micronesia
, and Polynesia
, as far as Hawaii
to the north and the Pitcairn Islands
to the southeast. In the eastern Pacific, it occurs from Costa Rica
to Panama
, and off the Galápagos Islands
.
Associated almost exclusively with coral reef
habitat
s, whitetip reef sharks are most often encountered around coral heads and ledges with high vertical relief, and additionally over sandy flats, in lagoon
s, and near drop-offs to deeper water. They prefer very clear water and rarely swim far from the bottom. This species is most common at a depth of 8 metre. On occasion they may enter water less than a meter deep, and there is an exceptional record of a whitetip reef shark being captured from a depth of 330 m (1,082.7 ft) in the Ryukyu Islands.
s and prominent ridges above, and are often followed by a small notch. The mouth has a distinct downward slant (imparting a disgruntled expression to the shark), with short furrows at the corners. There are 42–50 tooth rows in the upper jaw and 42–48 tooth rows in the lower jaw. Each tooth has a single narrow, smooth-edged cusp at the center, flanked by a pair of much smaller cusplets.
The first dorsal fin
is positioned well back on the body, closer to the pelvic than the pectoral fins. The second dorsal and anal fins are large, about half to three-quarters as high as the first dorsal fin. The broad, triangular pectoral fins originate at or slightly before the level of the fifth gill slit
. There is no ridge between the first and second dorsal fins. The lower lobe of the caudal fin is half the length of the upper, which has a strong notch near the tip. The dermal denticles are small and overlapping, usually with 7 horizontal ridges, giving the skin a smooth feel. The coloration is grayish to brownish above and white below, with a pattern of scattered small, dark spots unique to each individual. The tips of the first dorsal fin and upper caudal fin lobe, and sometimes also the second dorsal fin and lower caudal fin lobe, are bright white.
(Carcharhinus melanopterus) and the grey reef shark (Carcharhinus amblyrhynchos). The habitat preferences of this species overlap those of the other two, though it does not tend to frequent very shallow water like the blacktip reef shark, nor the outer reef like the grey reef shark. The whitetip reef shark swims with strong undulations of its body, and unlike other requiem sharks can lie motionless on the bottom and actively pump water over its gills for respiration
. This species is most active at night or during slack tide, and spends much of the day resting inside caves singly or in small groups, arranged in parallel or stacked atop one another. Off Hawaii, these sharks may be found sheltering inside underwater lava tube
s, while off Costa Rica they are often seen lying in the open on sandy flats.
Whitetip reef sharks generally remain within a highly localized area; only rarely do they undertake long movements, wandering for a while before settling down somewhere new. One study at Johnston Atoll
found that none of the sharks examined had moved more than 3 km (1.9 mi) away from their original capture location over periods of up to a year. Another study at Rangiroa Atoll in French Polynesia
found that, after more than three years, around 40% of the originally tagged sharks were still present on the same reef where they were first captured. An individual shark may rest inside the same cave for months to years. The daytime home range
of a whitetip reef shark is limited to approximately 0.05 square kilometre; at night this range increases to 1 square kilometre. These sharks are not territorial and share their home ranges with others of their species; they do not perform threat displays
.
Important predators of the whitetip reef shark include tiger shark
s (Galeocerdo cuvier), Galapagos shark
s (Carcharhinus galapagensis), and possibly also silvertip shark
s (Carcharhinus albimarginatus), though they usually occur at depths greater than those favored by whitetip reef sharks. An 80 cm (31.5 in) long whitetip reef shark has also been found in the stomach of a giant grouper
(Epinephelus lanceolatus), though these groupers are unlikely to be significant predators of this species due to their rarity. Known parasites of the whitetip reef shark include the copepod
Paralebion elongatus and the praniza (parasitic) larva
e of the isopod Gnathia grandilaris. While resting during the day, these sharks have been observed being cleaned by the wrasse
Bodianus diplotaenia and the goby
Elacatinus puncticulatus
. Unusually, there is also a report of seven whitetip reef sharks adopting a cleaning posture (mouth agape and gills flared) in the midst of a swarm of non-cleaning hyperiid
amphipods; the mechanical stimulation from the moving amphipods are thought to have evoked this behavior through their similarity to actual cleaner organisms.
s, squirrelfishes, snapper
s, damselfish
es, parrotfish
es, surgeonfishes, triggerfish
es, and goatfish
es, as well as octopus
, spiny lobster
s, and crab
s. The whitetip reef shark is highly responsive to the olfactory
, acoustic
, and electrical cues given off by potential prey, while its visual system is attuned more to movement and/or contrast than to object details. It is especially sensitive to natural and artificial low-frequency sounds in the 25–100 Hz range, which evoke struggling fish.
Whitetip reef sharks hunt primarily at night, when many fishes are asleep and easily taken. After dusk, groups of sharks methodically scour the reef, often breaking off pieces of coral in their vigorous pursuit of prey. Multiple sharks may target the same prey item, covering every exit route from a particular coral head. Each shark hunts for itself and in competition with the others in its group. Unlike blacktip reef sharks and grey reef sharks, whitetip reef sharks do not become more excited when feeding in groups and are unlikely to be stirred into a feeding frenzy
. Despite their nocturnal habits, whitetip reef sharks will hunt opportunistically in daytime. Off Borneo
, this species gathers around reef drop-offs to feed on food brought up by the rising current. Off Hawaii
, they follow Hawaiian monk seal
s (Monachus schauinslandi) and attempt to steal their catches. A whitetip reef shark can survive for six weeks without food.
s exhaust their supply of yolk, the yolk sac
is converted into a placenta
l connection through which the mother delivers nourishment for the remainder of gestation
. Mature females have a single functional ovary
, on the left side, and two functional uterus
es. The reproductive cycle is biennial.
Mating is initiated when up to five males follow closely behind a female and bite at her fins and body, possibly cued by pheromone
s indicating the female's readiness. Each male attempts to seize the female by engulfing one of her pectoral fins; at times two males might grasp a female on both sides simultaneously. Once engaged, the sharks sink to the bottom, whereupon the male (or males) rotates one of his claspers forward, inflates the associated siphon sac (a subcutaneous abdominal organ that takes in seawater that is used to flush sperm
into the female), and attempts to make contact with the female's vent. In many cases, the female resists by pressing her belly against the bottom and arching her tail; this may reflect mate choice
on her part. The male has a limited time in which to achieve copulation, as while he is holding the female's pectoral fin in his mouth he is being deprived of oxygen
. On the other hand, if the female is willing, the pair settles side-by-side with their heads pressed against the bottom and their bodies at an upward angle.
After a gestation period
of 10–13 months, females give birth to litters of 1–6 (usually 2–3) pups. The number of offspring is not correlated with female size; each female produces an estimated average of 12 pups over her entire lifetime. Parturition occurs from May to August (autumn and winter) in French Polynesia, in July (summer) off Enewetak Atoll, and in October (summer) off Australia. Females give birth while swimming, making violent twists and turns of their bodies; each pup takes under an hour to fully emerge. The newborns measure 52–60 cm (20.5–23.6 in) long and have relatively longer caudal fins than adults. This shark develops slowly compared to other requiem sharks; newborns grow at a rate of 16 cm (6.3 in) per year while adults grow as a rate of 2–4 cm (0.78740157480315–1.6 in) per year. Sexual maturity
is reached at a length of around 1.1 m (3.6 ft) and an age of 8–9 years, though mature males as small as 95 cm (37.4 in) long have been recorded from the Maldives
, suggesting regional variation in maturation size. On the Great Barrier Reef
, males live to 14 years and females to 19 years; the maximum lifespan of this shark may be upwards of 25 years. In 2008, a whitetip reef shark produced a single pup through possibly asexual
means at the Nyiregyhaza Centre in Hungary
; previous instances of asexual reproduction in sharks have been reported in the bonnethead
(Sphyrna tiburo) and the blacktip shark
(Carcharhinus limbatus).
discharge or a boat dropping anchor with food and respond within seconds. As of 2008, the International Shark Attack File
lists two provoked and three unprovoked attacks to this species. Whitetip reef sharks are well-suited to ecotourism
diving, and with conditioning they can be hand-fed by divers. In Hawaiian mythology
, the fidelity (i.e. "loyalty") of whitetip reef sharks to certain areas of the reef for years at a time may have inspired belief in ʻaumākua
, the spirits of family ancestors that take animal form and protect their descendants.
The whitetip reef shark is taken by fisheries
operating off Pakistan
, India
, Sri Lanka
, Madagascar
, and likely elsewhere, using longlines, gillnet
s, and trawls. The meat and liver
are eaten, though sharks from certain areas present a substantial risk of ciguatera poisoning (especially the liver, which contains a much higher concentration of the toxin than the meat). The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
, as its numbers have dropped in recent decades due to increasing, and thus far unregulated, fishing pressure in the tropics. Its restricted habitat, low dispersal, and slow reproduction are factors that limit this shark's capacity for recovering from overfishing
. On the Great Barrier Reef, populations of whitetip reef sharks in fishing zones have been reduced by 80% relative to no-entry zones. Furthermore, populations in no-take zones, where boats are allowed but fishing prohibited, exhibit levels of depletion comparable to fishing zones due to poaching
. Demographic models indicate that these depleted populations will continue to decline by 6.6–8.3% per year without additional conservation measures.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of requiem shark
Requiem shark
Requiem sharks are a family, Carcharhinidae, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas such as the tiger shark, the blue shark, the bull shark, and the milk shark.The name may be related to the French word for shark, "requin", itself of...
, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Carcharhinidae, and the only member of its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. A small shark usually not exceeding 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s, oval eyes with vertical pupils, and white-tipped dorsal
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
and caudal fins. One of the most common sharks found on Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s, the whitetip reef shark occurs as far west as South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
and as far east as Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
. It is typically found on or near the bottom in clear water, at a depth of 8 metre.
During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, 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...
s, and 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...
in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individual whitetip reef sharks may stay within a particular area of the reef for months to years, time and again returning to the same shelter. This species is viviparous, in which the developing 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...
s sustained by a placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
l connection to their mother. One of the few sharks in which mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
has been observed in the wild, receptive female whitetip reef sharks are followed by prospective males, who attempt to grasp her pectoral fin and maneuver the two of them into positions suitable for copulation. Females give birth to 1–6 pups every other year, after a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of 10–13 months.
Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though there are reports of ciguatera poisoning resulting from its consumption. The International Union for Conservation of Nature (IUCN) has assessed the whitetip reef shark as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
, noting that its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to over-exploitation
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
.
Taxonomy and phylogeny
The whitetip reef shark was first described by the German naturalist Eduard RüppellEduard Rüppell
Wilhelm Peter Eduard Simon Rüppell was a German naturalist and explorer. Rüppell is occasionally transliterated to "Rueppell" for the English alphabet....
as Carcharias obesus, in the 1837 Fische des Rothen Meeres (Fishes of the Red Sea). His choice of the specific epithet obesus was curious, given that this shark is actually quite slender. Later in 1837, Johannes Müller
Johannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
and Friedrich Henle
Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle was a German physician, pathologist and anatomist. He is credited with the discovery of the loop of Henle in the kidney. His essay "On Miasma and Contagia" was an early argument for the germ theory of disease...
moved this species into its own genus Triaenodon, from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
triaena meaning "trident", and odon meaning "tooth". As Rüppell did not originally designate a holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
, in 1960 a 31 cm (12.2 in) long specimen caught off Jeddah
Jeddah
Jeddah, Jiddah, Jidda, or Jedda is a city located on the coast of the Red Sea and is the major urban center of western Saudi Arabia. It is the largest city in Makkah Province, the largest sea port on the Red Sea, and the second largest city in Saudi Arabia after the capital city, Riyadh. The...
, Saudi Arabia
Saudi Arabia
The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
was made the species lectotype
Lectotype
In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...
. Other common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s for this shark include blunthead shark, light-tip shark, reef whitetip shark, and whitetip shark.
Once placed in the family Triakidae, the whitetip reef shark is now recognized by most authors as belonging to the family Carcharhinidae on the basis of morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
characters such as a full nictitating membrane
Nictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
, well-developed precaudal pit, strong lower caudal fin lobe, and scroll-like intestinal
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
valves. Morphological and molecular phylogenetic analyses suggest that the whitetip reef shark is grouped with the lemon sharks
Negaprion
Negaprion is a genus of requiem sharks, family Carcharhinidae, containing the two extant species of lemon sharks: the lemon shark of the Americas, and the sicklefin lemon shark of the Indo-Pacific...
(Negaprion) and the sliteye shark
Sliteye shark
The sliteye shark the only member of the genus Loxodon, is a shark of the family Carcharhinidae, found in the tropical waters of the Indo-West Pacific oceans between latitudes 34° N and 30° S, from depths of 7 to 100 m. Its length is up to about 95 cm....
(Loxodon) in occupying an intermediate position on the carcharhinid evolutionary tree, between most basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
genera (Galeocerdo, Rhizoprionodon
Rhizoprionodon
Rhizoprionodon is a genus of requiem sharks, family Carcharhinidae, commonly known as sharpnose sharks because of their long, pointed snouts.-Species:* Rhizoprionodon acutus...
, and Scoliodon) and the most derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
(Carcharhinus
Carcharhinus
Carcharhinus is the type genus of the requiem shark family, Carcharhinidae.- Species :* Carcharhinus acarenatus * Carcharhinus acronotus...
and Sphyrna
Sphyrna
Sphyrna is a genus of hammerhead sharks in the family Sphyrnidae. It currently consists of the following species:*Sphyrna corona S. Springer, 1940 *Sphyrna couardi Cadenat, 1951...
).
Distribution and habitat
The whitetip reef shark is distributed widely across the entire Indo-PacificIndo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
region. In the Indian Ocean, it occurs from northern KwaZulu-Natal
KwaZulu-Natal
KwaZulu-Natal is a province of South Africa. Prior to 1994, the territory now known as KwaZulu-Natal was made up of the province of Natal and the homeland of KwaZulu....
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
to the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
and the Indian subcontinent
Indian subcontinent
The Indian subcontinent, also Indian Subcontinent, Indo-Pak Subcontinent or South Asian Subcontinent is a region of the Asian continent on the Indian tectonic plate from the Hindu Kush or Hindu Koh, Himalayas and including the Kuen Lun and Karakoram ranges, forming a land mass which extends...
, including Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
, the Comoros
Comoros
The Comoros , officially the Union of the Comoros is an archipelago island nation in the Indian Ocean, located off the eastern coast of Africa, on the northern end of the Mozambique Channel, between northeastern Mozambique and northwestern Madagascar...
, the Aldabra Group
Aldabra Group
The Aldabra Group are part of the Outer Islands of the Seychelles, lying in the southwest of the island nation, 1000 kilometres from the capital, Victoria, on Mahé Island.The total land area of the Aldabra Group is 175.91 km²....
, the Seychelles
Seychelles
Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....
, Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
, and the Chagos Archipelago
Chagos Archipelago
The Chagos Archipelago , is a group of seven atolls comprising more than 60 individual tropical islands in the Indian Ocean; situated some due south of the Maldives archipelago. This chain of islands are the southernmost archipelago of the Chagos-Laccadive Ridge a long submarine mountain range...
. In the western and central Pacific, it is occurs from off southern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, and the Ryukyu Islands
Ryukyu Islands
The , also known as the , is a chain of islands in the western Pacific, on the eastern limit of the East China Sea and to the southwest of the island of Kyushu in Japan. From about 1829 until the mid 20th century, they were alternately called Luchu, Loochoo, or Lewchew, akin to the Mandarin...
, to the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
, and Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, to northern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, and is also found around numerous islands in Melanesia
Melanesia
Melanesia is a subregion of Oceania extending from the western end of the Pacific Ocean to the Arafura Sea, and eastward to Fiji. The region comprises most of the islands immediately north and northeast of Australia...
, Micronesia
Micronesia
Micronesia is a subregion of Oceania, comprising thousands of small islands in the western Pacific Ocean. It is distinct from Melanesia to the south, and Polynesia to the east. The Philippines lie to the west, and Indonesia to the southwest....
, and Polynesia
Polynesia
Polynesia is a subregion of Oceania, made up of over 1,000 islands scattered over the central and southern Pacific Ocean. The indigenous people who inhabit the islands of Polynesia are termed Polynesians and they share many similar traits including language, culture and beliefs...
, as far as Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
to the north and the Pitcairn Islands
Pitcairn Islands
The Pitcairn Islands , officially named the Pitcairn, Henderson, Ducie and Oeno Islands, form a group of four volcanic islands in the southern Pacific Ocean. The islands are a British Overseas Territory and overseas territory of the European Union in the Pacific...
to the southeast. In the eastern Pacific, it occurs from Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
to 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...
, and off 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...
.
Associated almost exclusively with coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s, whitetip reef sharks are most often encountered around coral heads and ledges with high vertical relief, and additionally over sandy flats, in lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s, and near drop-offs to deeper water. They prefer very clear water and rarely swim far from the bottom. This species is most common at a depth of 8 metre. On occasion they may enter water less than a meter deep, and there is an exceptional record of a whitetip reef shark being captured from a depth of 330 m (1,082.7 ft) in the Ryukyu Islands.
Description
A relatively small species, few whitetip reef sharks are longer than 1.6 m (5.2 ft). The maximum length this species attains is often given as 2.1 m (6.9 ft), though this was originally based on visual observations and may be dubious. The maximum reported weight is 18.3 kg (40.3 lb). The whitetip reef shark has a slim body and a short, broad head. The snout is flattened and blunt; there are large flaps of skin in front of the nares that are furled into tubes. The eyes are small and oval with vertical pupilPupil
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...
s and prominent ridges above, and are often followed by a small notch. The mouth has a distinct downward slant (imparting a disgruntled expression to the shark), with short furrows at the corners. There are 42–50 tooth rows in the upper jaw and 42–48 tooth rows in the lower jaw. Each tooth has a single narrow, smooth-edged cusp at the center, flanked by a pair of much smaller cusplets.
The first dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
is positioned well back on the body, closer to the pelvic than the pectoral fins. The second dorsal and anal fins are large, about half to three-quarters as high as the first dorsal fin. The broad, triangular pectoral fins originate at or slightly before the level of the fifth gill slit
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
. There is no ridge between the first and second dorsal fins. The lower lobe of the caudal fin is half the length of the upper, which has a strong notch near the tip. The dermal denticles are small and overlapping, usually with 7 horizontal ridges, giving the skin a smooth feel. The coloration is grayish to brownish above and white below, with a pattern of scattered small, dark spots unique to each individual. The tips of the first dorsal fin and upper caudal fin lobe, and sometimes also the second dorsal fin and lower caudal fin lobe, are bright white.
Biology and ecology
The whitetip reef shark is one of the three most common sharks inhabiting the reefs of the Indo-Pacific, the other two being the blacktip reef sharkBlacktip reef shark
The blacktip reef shark is a species of requiem shark, family Carcharhinidae, easily identified by the prominent black tips on its fins...
(Carcharhinus melanopterus) and the grey reef shark (Carcharhinus amblyrhynchos). The habitat preferences of this species overlap those of the other two, though it does not tend to frequent very shallow water like the blacktip reef shark, nor the outer reef like the grey reef shark. The whitetip reef shark swims with strong undulations of its body, and unlike other requiem sharks can lie motionless on the bottom and actively pump water over its gills for respiration
Aquatic respiration
Aquatic respiration is the process whereby an aquatic animal obtains oxygen from water.-Fish:In most fish respiration takes place through gills. Lungfish, however, possess one or two lungs...
. This species is most active at night or during slack tide, and spends much of the day resting inside caves singly or in small groups, arranged in parallel or stacked atop one another. Off Hawaii, these sharks may be found sheltering inside underwater lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...
s, while off Costa Rica they are often seen lying in the open on sandy flats.
Whitetip reef sharks generally remain within a highly localized area; only rarely do they undertake long movements, wandering for a while before settling down somewhere new. One study at Johnston Atoll
Johnston Atoll
Johnston Atoll is a atoll in the North Pacific Ocean about west of Hawaii. There are four islands located on the coral reef platform, two natural islands, Johnston Island and Sand Island, which have been expanded by coral dredging, as well as North Island and East Island , an additional two...
found that none of the sharks examined had moved more than 3 km (1.9 mi) away from their original capture location over periods of up to a year. Another study at Rangiroa Atoll in French Polynesia
French Polynesia
French Polynesia is an overseas country of the French Republic . It is made up of several groups of Polynesian islands, the most famous island being Tahiti in the Society Islands group, which is also the most populous island and the seat of the capital of the territory...
found that, after more than three years, around 40% of the originally tagged sharks were still present on the same reef where they were first captured. An individual shark may rest inside the same cave for months to years. The daytime home range
Home range
Home range is the area where an animal lives and travels in. It is closely related to, but not identical with, the concept of "territory".The concept that can be traced back to a publication in 1943 by W. H. Burt, who constructed maps delineating the spatial extent or outside boundary of an...
of a whitetip reef shark is limited to approximately 0.05 square kilometre; at night this range increases to 1 square kilometre. These sharks are not territorial and share their home ranges with others of their species; they do not perform threat displays
Shark threat display
Shark threat display, a type of agonistic display, is a behaviour observed in some sharks when they feel threatened or protective. It consists of a contorting of the body into a series of "ritualized" postures coupled with an exaggerated swimming style...
.
Important predators of the whitetip reef shark include 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 (Galeocerdo cuvier), Galapagos shark
Galapagos shark
The Galapagos shark is a species of requiem shark, family Carcharhinidae, found worldwide. This species favors clear reef environments around oceanic islands, where it is often the most abundant shark species...
s (Carcharhinus galapagensis), and possibly also silvertip shark
Silvertip shark
The silvertip shark is a large species of requiem shark, family Carcharhinidae, with a fragmented distribution throughout the tropical Indian and Pacific Oceans. This species is often encountered around offshore islands and coral reefs, and has been known to dive to a depth of 800 m...
s (Carcharhinus albimarginatus), though they usually occur at depths greater than those favored by whitetip reef sharks. An 80 cm (31.5 in) long whitetip reef shark has also been found in the stomach of a giant grouper
Giant grouper
The giant grouper , also known as the brindle bass, brown spotted cod, or bumblebee grouper and as the Queensland groper in Australia, is the largest bony fish found in coral reefs, and the aquatic emblem of Queensland, Australia. It is found throughout the Indo-Pacific region, with the exception...
(Epinephelus lanceolatus), though these groupers are unlikely to be significant predators of this species due to their rarity. Known parasites of the whitetip reef shark include the copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
Paralebion elongatus and the praniza (parasitic) larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e of the isopod Gnathia grandilaris. While resting during the day, these sharks have been observed being cleaned by the 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....
Bodianus diplotaenia and the 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...
Elacatinus puncticulatus
Elacatinus puncticulatus
Elacatinus puncticulatus is a Goby from the Eastern CentralPacific. It occasionally makes its way into the aquarium trade. It grows to a size of 4.4 cm in length....
. Unusually, there is also a report of seven whitetip reef sharks adopting a cleaning posture (mouth agape and gills flared) in the midst of a swarm of non-cleaning hyperiid
Hyperiidae
Hyperiidae is a family of amphipods, containing the following genera:*Euthemisto Bovallius, 1887*Hyperia Latreille in Desmarest, 1823*Hyperiella Bovallius, 1887*Hyperoche Bovallius, 1887*Laxohyperia M. Vinogradov & Volkov, 1982...
amphipods; the mechanical stimulation from the moving amphipods are thought to have evoked this behavior through their similarity to actual cleaner organisms.
Feeding
With its slender, lithe body, the whitetip reef shark specializes in wriggling into narrow crevices and holes in the reef and extracting prey inaccessible to other reef sharks. Alternatively, it is rather clumsy when attempting to take food suspended in open water. This species feeds mainly on bony fishes, including eelEel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...
s, squirrelfishes, snapper
Lutjanidae
Snappers are a family of perciform fish, mainly marine but with some members inhabiting estuaries, feeding in freshwater. Some are important food fish. One of the best known is the red snapper....
s, damselfish
Damselfish
Damselfish comprise the family Pomacentridae except those of the genera Amphiprion and Premnas. They can grow up to long. While most are marine, a few species inhabit the lower stretches of rivers in freshwater. Damselfish usually have bright colors. in tropical coral reefs, and many of those are...
es, parrotfish
Parrotfish
Parrotfishes are a group of fishes that traditionally had been considered a family , but now often are considered a subfamily of the wrasses. They are found in relatively shallow tropical and subtropical oceans throughout the world, but with the largest species richness in the Indo-Pacific...
es, surgeonfishes, triggerfish
Triggerfish
Triggerfishes are about 40 species of often brightly colored fishes of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacific...
es, and goatfish
Goatfish
Goatfishes are tropical marine perciform fish of the family Mullidae. Seldom found in brackish waters, goatfish are most associated with the reefs of the Atlantic, Indian, and Pacific Oceans...
es, as well as 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...
, spiny lobster
Spiny lobster
Spiny lobsters, also known as langouste or rock lobsters, are a family of about 45 species of achelate crustaceans, in the Decapoda Reptantia...
s, and 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...
s. The whitetip reef shark is highly responsive to the olfactory
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...
, acoustic
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
, and electrical cues given off by potential prey, while its visual system is attuned more to movement and/or contrast than to object details. It is especially sensitive to natural and artificial low-frequency sounds in the 25–100 Hz range, which evoke struggling fish.
Whitetip reef sharks hunt primarily at night, when many fishes are asleep and easily taken. After dusk, groups of sharks methodically scour the reef, often breaking off pieces of coral in their vigorous pursuit of prey. Multiple sharks may target the same prey item, covering every exit route from a particular coral head. Each shark hunts for itself and in competition with the others in its group. Unlike blacktip reef sharks and grey reef sharks, whitetip reef sharks do not become more excited when feeding in groups and are unlikely to be stirred into a feeding frenzy
Feeding frenzy
In ecology, a feeding frenzy is a situation where oversaturation of a supply of food leads to rapid feeding by predatory animals. For example, a large school of fish can cause nearby sharks to enter a feeding frenzy. This can cause the sharks to go wild, biting anything that moves, including each...
. Despite their nocturnal habits, whitetip reef sharks will hunt opportunistically in daytime. Off Borneo
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
, this species gathers around reef drop-offs to feed on food brought up by the rising current. Off Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, they follow Hawaiian monk seal
Hawaiian Monk Seal
The Hawaiian monk seal, Monachus schauinslandi, is an endangered species of earless seal in the Phocidae family that is endemic to the Hawaiian Islands....
s (Monachus schauinslandi) and attempt to steal their catches. A whitetip reef shark can survive for six weeks without food.
Life history
Like other members of its family, the whitetip reef shark is viviparous; once the developing embryoEmbryo
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...
s exhaust their supply of yolk, the yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
is converted into a placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
l connection through which the mother delivers nourishment for the remainder of gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
. Mature females have a single functional ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
, on the left side, and two functional uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
es. The reproductive cycle is biennial.
Mating is initiated when up to five males follow closely behind a female and bite at her fins and body, possibly cued by pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
s indicating the female's readiness. Each male attempts to seize the female by engulfing one of her pectoral fins; at times two males might grasp a female on both sides simultaneously. Once engaged, the sharks sink to the bottom, whereupon the male (or males) rotates one of his claspers forward, inflates the associated siphon sac (a subcutaneous abdominal organ that takes in seawater that is used to flush sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
into the female), and attempts to make contact with the female's vent. In many cases, the female resists by pressing her belly against the bottom and arching her tail; this may reflect mate choice
Mate choice
Mate choice, or intersexual selection, is an evolutionary process in which selection of a mate depends on attractiveness of its traits. It is one of two components of sexual selection...
on her part. The male has a limited time in which to achieve copulation, as while he is holding the female's pectoral fin in his mouth he is being deprived of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. On the other hand, if the female is willing, the pair settles side-by-side with their heads pressed against the bottom and their bodies at an upward angle.
After a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of 10–13 months, females give birth to litters of 1–6 (usually 2–3) pups. The number of offspring is not correlated with female size; each female produces an estimated average of 12 pups over her entire lifetime. Parturition occurs from May to August (autumn and winter) in French Polynesia, in July (summer) off Enewetak Atoll, and in October (summer) off Australia. Females give birth while swimming, making violent twists and turns of their bodies; each pup takes under an hour to fully emerge. The newborns measure 52–60 cm (20.5–23.6 in) long and have relatively longer caudal fins than adults. This shark develops slowly compared to other requiem sharks; newborns grow at a rate of 16 cm (6.3 in) per year while adults grow as a rate of 2–4 cm (0.78740157480315–1.6 in) per year. Sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
is reached at a length of around 1.1 m (3.6 ft) and an age of 8–9 years, though mature males as small as 95 cm (37.4 in) long have been recorded from the Maldives
Maldives
The Maldives , , officially Republic of Maldives , also referred to as the Maldive Islands, is an island nation in the Indian Ocean formed by a double chain of twenty-six atolls oriented north-south off India's Lakshadweep islands, between Minicoy Island and...
, suggesting regional variation in maturation size. On the Great Barrier Reef
Great Barrier Reef
The Great Barrier Reef is the world'slargest reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres over an area of approximately...
, males live to 14 years and females to 19 years; the maximum lifespan of this shark may be upwards of 25 years. In 2008, a whitetip reef shark produced a single pup through possibly asexual
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
means at the Nyiregyhaza Centre in Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
; previous instances of asexual reproduction in sharks have been reported in the bonnethead
Bonnethead
The bonnethead shark or shovelhead, Sphyrna tiburo, is a member of the hammerhead shark genus Sphyrna. The Greek word sphyrna translates as hammer, referring to the shape of this shark's head - tiburo is the Taino word for shark....
(Sphyrna tiburo) and the blacktip shark
Blacktip shark
The blacktip shark is a species of requiem shark, family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean...
(Carcharhinus limbatus).
Human interactions
Fearless and curious, whitetip reef sharks may approach swimmers closely but are seldom aggressive unless provoked. However, these sharks readily attempt, and quite boldly, to steal catches from spear fishers, which has resulted in several people being bitten in the process. In some places, local whitetip reef sharks have learned to associate the sound of a speargunSpeargun
A speargun is an underwater fishing implement designed to fire a spear at fish.The basic components of a speargun are:A spear, a stock/barrel, and a handle/grip containing a trigger mechanism...
discharge or a boat dropping anchor with food and respond within seconds. As of 2008, the International Shark Attack File
International Shark Attack File
The International Shark Attack File is a global database of shark attacks. It began as an attempt to catalogue shark attacks on servicemen during World War II. The Office of Naval Research funded it from 1958 until 1968. During that time a panel of shark experts developed a standard system for...
lists two provoked and three unprovoked attacks to this species. Whitetip reef sharks are well-suited to ecotourism
Ecotourism
Ecotourism is a form of tourism visiting fragile, pristine, and usually protected areas, intended as a low impact and often small scale alternative to standard commercial tourism...
diving, and with conditioning they can be hand-fed by divers. In Hawaiian mythology
Hawaiian mythology
Hawaiian mythology refers to the legends, historical tales and sayings of the ancient Hawaiian people. It is considered a variant of a more general Polynesian mythology, developing its own unique character for several centuries before about 1800. It is associated with the Hawaiian religion...
, the fidelity (i.e. "loyalty") of whitetip reef sharks to certain areas of the reef for years at a time may have inspired belief in ʻaumākua
Aumakua
In Hawaiian mythology, an aumakua is a family god, often a deified ancestor. The Hawaiian plural of aumakua is nā aumākua , although in English the plural is usually aumakuas. Nā aumākua frequently manifested as animals such as sharks or owls. Nā aumākua were worshipped at localities where they...
, the spirits of family ancestors that take animal form and protect their descendants.
The whitetip reef shark is taken by fisheries
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
operating off Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
, Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, and likely elsewhere, using longlines, gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
s, and trawls. The meat and liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
are eaten, though sharks from certain areas present a substantial risk of ciguatera poisoning (especially the liver, which contains a much higher concentration of the toxin than the meat). The International Union for Conservation of Nature (IUCN) has assessed this species as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
, as its numbers have dropped in recent decades due to increasing, and thus far unregulated, fishing pressure in the tropics. Its restricted habitat, low dispersal, and slow reproduction are factors that limit this shark's capacity for recovering from overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
. On the Great Barrier Reef, populations of whitetip reef sharks in fishing zones have been reduced by 80% relative to no-entry zones. Furthermore, populations in no-take zones, where boats are allowed but fishing prohibited, exhibit levels of depletion comparable to fishing zones due to poaching
Poaching
Poaching is the illegal taking of wild plants or animals contrary to local and international conservation and wildlife management laws. Violations of hunting laws and regulations are normally punishable by law and, collectively, such violations are known as poaching.It may be illegal and in...
. Demographic models indicate that these depleted populations will continue to decline by 6.6–8.3% per year without additional conservation measures.