Short-tail stingray
Encyclopedia
The short-tail stingray or smooth stingray (Dasyatis brevicaudata) is a common species
of stingray
in the family
Dasyatidae. It occurs off southern Africa
, typically offshore at a depth of 180–480 m (590.6–1,574.8 ft), and off southern Australia
and New Zealand
, from the intertidal zone
to a depth of 156 m (511.8 ft). It is mostly bottom-dwelling in nature and can be found across a range of habitat
s from estuaries to reef
s, but also frequently swims into open water. The largest stingray in the world, this heavy-bodied species grows upwards of 2.1 m (6.9 ft) across and 350 kg (771.6 lb) in weight. Its plain-colored, diamond-shaped pectoral fin disc is characterized by a lack of dermal denticles even in adults, and white pores beside the head on either side. Its tail is usually shorter than the disc and thick at the base, with a midline row of large thorns in front of the stinging spine and dorsal and ventral fin folds behind.
The diet of the short-tail stingray consists of invertebrate
s and bony fishes, including burrowing and midwater species. It tends to remain within a relatively limited area throughout the year, preferring deeper waters during the winter, and is not known to perform long migrations
. Large aggregations of rays form seasonally at certain locations, such as in the summer at the Poor Knight Islands off New Zealand. Both birthing and mating have been documented within the aggregations at Poor Knights. This species is aplacental viviparous, with the developing embryo
s sustained by histotroph ("uterine milk") produced by the mother; the litter size is 6–10. The short-tail stingray is not aggressive but is capable of inflicting a potentially lethal wound with its long, venom
ous sting. It is caught incidentally
by commercial
and recreational fisheries
throughout its range, usually surviving to be released. Because its population does not appear threatened by human activity, the International Union for Conservation of Nature (IUCN) has listed it under Least Concern
.
, Curator
of the Otago Museum
, from a female specimen
1.2 m (3.9 ft) across caught off Dunedin
in New Zealand. He published his account in an 1875 issue of the scientific journal
Annals and Magazine of Natural History, in which he named the new species Trygon brevicaudata, derived from the Latin
brevis ("short") and cauda ("tail"). Subsequent authors have assigned this species to the now-obsolete genus Bathytoshia, and then to Dasyatis
. The short-tail stingray may also be referred to as giant black ray, giant stingray, New Zealand short-tail stingaree, Schreiners ray, short-tailed stingaree, shorttail black stingray, and smooth short-tailed stingray. It is closely related to the similar-looking but smaller pitted stingray
(Dasyatis matsubarai) of the northwestern Pacific.
waters of the Southern Hemisphere
. Off southern Africa, it has been reported from Cape Town
in South Africa
to the mouth of the Zambezi River in Mozambique
. Along the southern Australian coast, it is found from Shark Bay
in Western Australia
to Maroochydore in Queensland
, including Tasmania
. In New Zealand
waters, it occurs off North Island
and the Chatham Islands
, and rarely off South Island
and the Kermadec Islands
. Records from northern Australia and Thailand
likely represent misidentifications of Himantura fai and D. matsubarai respectively. Over the past few decades, its range and numbers off southeastern Tasmania have grown, possibly as a result of climate change
.
Off southern Africa, the short-tail stingray is rare in shallow water and most often found over offshore banks at a depth of 180 to 480 m (590.6 to 1,574.8 ft). On the other hand, off Australia and New Zealand it is found from the intertidal zone
to no deeper than 156 m (511.8 ft). Australian and New Zealand rays are most abundant in the shallows during the summer. A tracking study conducted on two New Zealand rays suggests that they shift to deeper waters during the winter, but do not undertake long-distance migration
s. The short-tail stingray is mainly bottom-dwelling in nature, inhabiting a variety of environments including brackish estuaries, sheltered bay
s and inlet
s, sandy flats, rocky reef
s, and the outer continental shelf
. However, it also makes regular forays upward into the middle of the water column.
shape and is slightly wider than long. The leading margins of the disc are very gently convex, and converge on a blunt, broadly triangular snout. The eyes are small and immediately followed by much larger spiracle
s. The widely spaced nostrils are long and narrow; between them is a short, skirt-shaped curtain of skin with a fringed posterior margin. The modestly sized mouth has an evenly arched lower jaw, prominent grooves at the corners, and 5–7 papillae (nipple-like structures) on the floor. Additional, tiny papillae are scattered on the nasal curtain and outside the lower jaw. The teeth are arranged with a quincunx
pattern into flattened surfaces; each tooth is small and blunt, with a roughly diamond-shaped base. There are 45–55 tooth rows in either jaw. The pelvic fins are somewhat large and rounded at the tips.
The tail is usually shorter than the disc and bears one, sometimes two serrated stinging spines on the upper surface, about halfway along its length. It is broad and flattened until the base of the sting; after, it tapers rapidly and there is a prominent ventral fin fold running almost to the sting tip, as well as a low dorsal ridge. Dermal denticles are only found on the tail, with at least one thorn appearing on the tail base by a disc width of 45 cm (17.7 in). Adults have a midline row of large, backward-pointing, spear-like thorns or flattened tubercles in front of the sting, as well as much smaller, conical thorns behind the sting covering the tail to the tip. The dorsal coloration is grayish brown, darkening towards the tip of the tail and above the eyes, with a line of white pores flanking the head on either side. The underside is whitish, darkening towards the fin margins and beneath the tail. Albino individuals have been reported. The short-tail stingray is the largest stingray species, known to reach at least 2.1 m (6.9 ft) in width, 4.3 m (14.1 ft) in length, and 350 kg (771.6 lb) in weight. Reliable observers off New Zealand have reported sighting individuals almost 3 m (9.8 ft) across. Mature females are about a third larger
than mature males.
the water and create an audible "bang". It is known to form large seasonal aggregations; a well-known example occurs every summer (January to April) at the Poor Knights Islands
off New Zealand, particularly under the rocky archways. In some areas it moves with the rising tide
into very shallow water. Individual rays tend to stay inside a relatively small home range with a radius of under 25 km (15.5 mi). Captive experiments have shown it capable of detecting magnetic field
s via its electroreceptive
ampullae of Lorenzini
, which in nature may be employed for navigation.
The short-tail stingray forages for food both during the day and at night. It feeds primarily on benthic bony fishes and invertebrate
s, such as molluscs and crustacean
s. The lateral line
system on its underside allows it to detect the minute water jets produced by buried bivalves and spoon worm
s, which are then extracted via suction; the excess water is expelled through the spiracles. Fishes and invertebrates from open water, including salp
s and hyperiid
amphipods, are also eaten in significant quantities. Off South Africa, this ray has been observed patrolling the egg beds of the chokka squid (Loligo vulgaris reynaudii) during mass spawnings, capturing squid that descend to the bottom to spawn. The short-tail stingray has few predators due to its size; these include the copper shark (Carcharhinus brachyurus), the smooth hammerhead
(Sphryna zygaena), the great white shark
(Carcharodon carcharias), and the killer whale (Orcinus orca). When threatened, it raises its tail warningly over its back like a scorpion
. Smaller fishes have been observed using swimming rays for cover while hunting their own prey. Known parasites of this species include the nematode
Echinocephalus overstreeti, and the monogenea
ns Heterocotyle tokoloshei and Dendromonocotyle sp.
The summer aggregations of the short-tail stingray at the Poor Knights Islands seem to at least partly serve a reproductive purpose, as both mating and birthing have been observed among the gathered rays. Courtship and mating take place in mid-water, and it has been speculated that the rising current flowing continuously through the narrow archways aids the rays in maintaining their position. Each receptive female may be followed by several males, who attempt to bite and grip her disc. One or two males may be dragged by the female for hours before she accedes; the successful male flips upside-down beneath her, inserting one of his claspers into her vent and rhythmically waving his tail from side to side. Copulation lasts 3–5 minutes. Females in captivity have been observed mating with up to three different males in succession.
Like other stingrays, the short-tail stingray is aplacental viviparous: once the developing embryo
s exhaust their yolk supply, they are provisioned with histotroph ("uterine milk", enriched with protein
s, lipid
s and mucus
) produced by the mother and delivered through specialized extensions of the uterine epithelium
called "trophonemata". Females bear litters of 6–10 pups in the summer; males appear to assist in the process by nudging the female's abdomen with their snouts. Females are ready to mate again shortly after giving birth. Newborns measure 32–36 cm (12.6–14.2 in) across.
in Western Australia, many short-tail stingrays, thorntail stingray
s (D. thetidis), and Australian bull ray
s (Myliobatis australis) regularly gather to be hand-fed fish scraps; the number of visitors has steadily increased in recent years, and there is interest in developing the site as a permanent tourist attraction. However, if startled or harassed this species is capable of inflicting a serious, even fatal wound with its sting. The sting can measure over 30 cm (11.8 in) long and penetrate most types of footwear, including kevlar
bootee
s; its mucous sheath contains a toxin
that causes necrosis
. The most dangerous injuries involve damage to a vital organ, massive blood loss, and/or secondary septicemia or tetanus
. There have been cases where a startled ray had jumped out of the water and pierced a wader's chest cavity. This species is responsible for the majority of stingray injuries off New Zealand.
Throughout its range, the short-tail stingray is caught incidentally
by various commercial fisheries
using trawls, Danish and purse seines, longlines and set lines, and drag and set nets
. It is also caught by recreational fishers
using hook-and-line (from boats or the shore), spears, and harpoon
s. Most individuals caught are released alive; often fishers cut off their tails beforehand for safety, though this practice does not seem to have a significant impact on the rays' long-term survival. Sport fishers occasionally keep captured rays for meat or angling competitions; a small number are also kept for display in public aquarium
s, and it has reproduced in captivity. As it survives fishing activities well and remains common throughout its range, the International Union for Conservation of Nature (IUCN) has assessed the short-tail stingray as Least Concern
. Within most of this species' range off New Zealand, targeting it commercially is prohibited.
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 stingray
Myliobatiformes
Myliobatiformes is one of the four orders of batoids, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown that the myliobatiforms are a monophyletic group, and that its more derived members evolved their...
in the 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...
Dasyatidae. It occurs off southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
, typically offshore at a depth of 180–480 m (590.6–1,574.8 ft), and off southern 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 New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, from the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
to a depth of 156 m (511.8 ft). It is mostly bottom-dwelling in nature and can be found across a range of 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 from estuaries to reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s, but also frequently swims into open water. The largest stingray in the world, this heavy-bodied species grows upwards of 2.1 m (6.9 ft) across and 350 kg (771.6 lb) in weight. Its plain-colored, diamond-shaped pectoral fin disc is characterized by a lack of dermal denticles even in adults, and white pores beside the head on either side. Its tail is usually shorter than the disc and thick at the base, with a midline row of large thorns in front of the stinging spine and dorsal and ventral fin folds behind.
The diet of the short-tail stingray consists of invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and bony fishes, including burrowing and midwater species. It tends to remain within a relatively limited area throughout the year, preferring deeper waters during the winter, and is not known to perform long migrations
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
. Large aggregations of rays form seasonally at certain locations, such as in the summer at the Poor Knight Islands off New Zealand. Both birthing and mating have been documented within the aggregations at Poor Knights. This species is aplacental viviparous, with 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 histotroph ("uterine milk") produced by the mother; the litter size is 6–10. The short-tail stingray is not aggressive but is capable of inflicting a potentially lethal wound with its long, venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous sting. It is caught incidentally
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
by commercial
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
and recreational fisheries
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
throughout its range, usually surviving to be released. Because its population does not appear threatened by human activity, the International Union for Conservation of Nature (IUCN) has listed it under Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
.
Taxonomy
The original description of the short-tail stingray was made by Frederick Wollaston HuttonFrederick Wollaston Hutton
Captain Frederick Wollaston Hutton, FRS, was an English scientist who applied the theory of natural selection to explain the origins and nature of the natural history of New Zealand.- Biography :...
, Curator
Curator
A curator is a manager or overseer. Traditionally, a curator or keeper of a cultural heritage institution is a content specialist responsible for an institution's collections and involved with the interpretation of heritage material...
of the Otago Museum
Otago museum
The Otago Museum is situated in Dunedin, New Zealand. It was founded in 1868 and has a collection of over two million artefacts and specimens from the fields of natural history and ethnography...
, from a female specimen
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...
1.2 m (3.9 ft) across caught off Dunedin
Dunedin
Dunedin is the second-largest city in the South Island of New Zealand, and the principal city of the Otago Region. It is considered to be one of the four main urban centres of New Zealand for historic, cultural, and geographic reasons. Dunedin was the largest city by territorial land area until...
in New Zealand. He published his account in an 1875 issue of the scientific journal
Scientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Annals and Magazine of Natural History, in which he named the new species Trygon brevicaudata, derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
brevis ("short") and cauda ("tail"). Subsequent authors have assigned this species to the now-obsolete genus Bathytoshia, and then to Dasyatis
Dasyatis
Dasyatis is a genus of stingray. The members of the genus Neotrygon were formerly included in Dasyatis.-Species:...
. The short-tail stingray may also be referred to as giant black ray, giant stingray, New Zealand short-tail stingaree, Schreiners ray, short-tailed stingaree, shorttail black stingray, and smooth short-tailed stingray. It is closely related to the similar-looking but smaller pitted stingray
Pitted stingray
The pitted stingray is a species of stingray in the family Dasyatidae, endemic to the waters around Japan and the Sea of Japan. It typically found near the coast at depths of , but may also venture into the open sea. Measuring up to across, the pitted stingray has a diamond-shaped pectoral fin...
(Dasyatis matsubarai) of the northwestern Pacific.
Distribution and habitat
The short-tail stingray is common and widely distributed in the temperateTemperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
waters of the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
. Off southern Africa, it has been reported from Cape Town
Cape Town
Cape Town is the second-most populous city in South Africa, and the provincial capital and primate city of the Western Cape. As the seat of the National Parliament, it is also the legislative capital of the country. It forms part of the City of Cape Town metropolitan municipality...
in 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 mouth of the Zambezi River in Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
. Along the southern Australian coast, it is found from Shark Bay
Shark Bay
Shark Bay is a World Heritage listed bay in Western Australia. The term may also refer to:* the locality of Shark Bay, now known as Denham* Shark Bay Marine Park* Shark Bay , a shark exhibit at Sea World, Gold Coast, Australia* Shire of Shark Bay...
in Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
to Maroochydore in Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, including Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
. In New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
waters, it occurs off North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
and the Chatham Islands
Chatham Islands
The Chatham Islands are an archipelago and New Zealand territory in the Pacific Ocean consisting of about ten islands within a radius, the largest of which are Chatham Island and Pitt Island. Their name in the indigenous language, Moriori, means Misty Sun...
, and rarely off South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
and the Kermadec Islands
Kermadec Islands
The Kermadec Islands are a subtropical island arc in the South Pacific Ocean northeast of New Zealand's North Island, and a similar distance southwest of Tonga...
. Records from northern Australia and Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
likely represent misidentifications of Himantura fai and D. matsubarai respectively. Over the past few decades, its range and numbers off southeastern Tasmania have grown, possibly as a result of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
.
Off southern Africa, the short-tail stingray is rare in shallow water and most often found over offshore banks at a depth of 180 to 480 m (590.6 to 1,574.8 ft). On the other hand, off Australia and New Zealand it is found from the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
to no deeper than 156 m (511.8 ft). Australian and New Zealand rays are most abundant in the shallows during the summer. A tracking study conducted on two New Zealand rays suggests that they shift to deeper waters during the winter, but do not undertake long-distance migration
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
s. The short-tail stingray is mainly bottom-dwelling in nature, inhabiting a variety of environments including brackish estuaries, sheltered bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s and inlet
Inlet
An inlet is a narrow body of water between islands or leading inland from a larger body of water, often leading to an enclosed body of water, such as a sound, bay, lagoon or marsh. In sea coasts an inlet usually refers to the actual connection between a bay and the ocean and is often called an...
s, sandy flats, rocky reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s, and the outer continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
. However, it also makes regular forays upward into the middle of the water column.
Description
Heavily built and characteristically smooth, the pectoral fin disc of the short-tail stingray has a rather angular, rhomboidRhomboid
Traditionally, in two-dimensional geometry, a rhomboid is a parallelogram in which adjacent sides are of unequal lengths and angles are oblique.A parallelogram with sides of equal length is a rhombus but not a rhomboid....
shape and is slightly wider than long. The leading margins of the disc are very gently convex, and converge on a blunt, broadly triangular snout. The eyes are small and immediately followed by much larger spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s. The widely spaced nostrils are long and narrow; between them is a short, skirt-shaped curtain of skin with a fringed posterior margin. The modestly sized mouth has an evenly arched lower jaw, prominent grooves at the corners, and 5–7 papillae (nipple-like structures) on the floor. Additional, tiny papillae are scattered on the nasal curtain and outside the lower jaw. The teeth are arranged with a quincunx
Quincunx
A quincunx is a geometric pattern consisting of five points arranged in a cross, that is five coplanar points, four of them forming a square or rectangle and a fifth at its center...
pattern into flattened surfaces; each tooth is small and blunt, with a roughly diamond-shaped base. There are 45–55 tooth rows in either jaw. The pelvic fins are somewhat large and rounded at the tips.
The tail is usually shorter than the disc and bears one, sometimes two serrated stinging spines on the upper surface, about halfway along its length. It is broad and flattened until the base of the sting; after, it tapers rapidly and there is a prominent ventral fin fold running almost to the sting tip, as well as a low dorsal ridge. Dermal denticles are only found on the tail, with at least one thorn appearing on the tail base by a disc width of 45 cm (17.7 in). Adults have a midline row of large, backward-pointing, spear-like thorns or flattened tubercles in front of the sting, as well as much smaller, conical thorns behind the sting covering the tail to the tip. The dorsal coloration is grayish brown, darkening towards the tip of the tail and above the eyes, with a line of white pores flanking the head on either side. The underside is whitish, darkening towards the fin margins and beneath the tail. Albino individuals have been reported. The short-tail stingray is the largest stingray species, known to reach at least 2.1 m (6.9 ft) in width, 4.3 m (14.1 ft) in length, and 350 kg (771.6 lb) in weight. Reliable observers off New Zealand have reported sighting individuals almost 3 m (9.8 ft) across. Mature females are about a third larger
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
than mature males.
Biology and ecology
The short-tail stingray is usually slow-moving but can achieve sudden bursts of speed, flapping its pectoral fins with enough force to cavitateCavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
the water and create an audible "bang". It is known to form large seasonal aggregations; a well-known example occurs every summer (January to April) at the Poor Knights Islands
Poor Knights Islands
The Poor Knights Islands are a group of islands off the east coast of the Northland Region of the North Island of New Zealand. They are located to the northeast of Whangarei, and lie offshore half way between Bream Head and Cape Brett. Uninhabited since the 1820s, they are a nature reserve and...
off New Zealand, particularly under the rocky archways. In some areas it moves with the rising tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
into very shallow water. Individual rays tend to stay inside a relatively small home range with a radius of under 25 km (15.5 mi). Captive experiments have shown it capable of detecting magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
s via its electroreceptive
Electroreception
Electroreception is the biological ability to perceive natural electrical stimuli. It has been observed only in aquatic or amphibious animals, since water is a much better conductor than air. Electroreception is used in electrolocation and for electrocommunication.- Overview :Electroreception is...
ampullae of Lorenzini
Ampullae of Lorenzini
The ampullae of Lorenzini are special sensing organs called electroreceptors, forming a network of jelly-filled pores. They are mostly discussed as being found in cartilaginous fishes ; however, they are also reported to be found in Chondrostei such as Reedfish and sturgeon. Lungfish have also been...
, which in nature may be employed for navigation.
The short-tail stingray forages for food both during the day and at night. It feeds primarily on benthic bony fishes and invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, such as molluscs and 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. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
system on its underside allows it to detect the minute water jets produced by buried bivalves and spoon worm
Echiura
The Echiura, or spoon worms, are a small group of marine animals. They are often considered to be a group of annelids, although they lack the segmented structure found in other members of that group, and so may also be treated as a separate phylum...
s, which are then extracted via suction; the excess water is expelled through the spiracles. Fishes and invertebrates from open water, including salp
Salp
A salp or salpa is a barrel-shaped, planktonic tunicate. It moves by contracting, thus pumping water through its gelatinous body...
s and 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, are also eaten in significant quantities. Off South Africa, this ray has been observed patrolling the egg beds of the chokka squid (Loligo vulgaris reynaudii) during mass spawnings, capturing squid that descend to the bottom to spawn. The short-tail stingray has few predators due to its size; these include the copper shark (Carcharhinus brachyurus), the smooth hammerhead
Smooth hammerhead
The smooth hammerhead is a species of hammerhead shark, family Sphyrnidae, so named because of the distinctive shape of the head, which is flattened and laterally extended into a hammer shape , without an indentation in the middle of the front margin...
(Sphryna zygaena), the great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
(Carcharodon carcharias), and the killer whale (Orcinus orca). When threatened, it raises its tail warningly over its back like a 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...
. Smaller fishes have been observed using swimming rays for cover while hunting their own prey. Known parasites of this species include the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
Echinocephalus overstreeti, and the monogenea
Monogenea
Monogenea are a group of largely ectoparasitic members of the flatworm phylum Platyhelminthes, class Monogenea.-Characteristics:Monogenea are very small parasitic flatworms mainly found on skin or gills of fish....
ns Heterocotyle tokoloshei and Dendromonocotyle sp.
Life history
Like other stingrays, the short-tail stingray is aplacental viviparous: once 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 exhaust their yolk supply, they are provisioned with histotroph ("uterine milk", enriched with protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s and mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
) produced by the mother and delivered through specialized extensions of the uterine epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
called "trophonemata". Females bear litters of 6–10 pups in the summer; males appear to assist in the process by nudging the female's abdomen with their snouts. Females are ready to mate again shortly after giving birth. Newborns measure 32–36 cm (12.6–14.2 in) across.
Human interactions
Curious and unaggressive, the short-tail stingray may approach humans and can be trained to be hand-fed. At Hamelin BayHamelin Bay, Western Australia
Hamelin Bay is a bay and a locality on the south west coast of Western Australia between Cape Leeuwin and Cape Naturaliste. It is named after French explorer Jacques Félix Emmanuel Hamelin who sailed through the area in about 1801...
in Western Australia, many short-tail stingrays, thorntail stingray
Thorntail stingray
The thorntail stingray, black stingray, or longtail stingray is a species of stingray in the family Dasyatidae. It is found off southern Africa, Australia, and New Zealand from the intertidal zone to a depth of . This bottom-dweller inhabits soft-bottomed habitats such as lagoons, estuaries, and...
s (D. thetidis), and Australian bull ray
Australian bull ray
The Australian bull ray or southern eagle ray is a large eagle ray of temperate waters of Australia. It is possible that it is the same species as the New Zealand eagle ray ....
s (Myliobatis australis) regularly gather to be hand-fed fish scraps; the number of visitors has steadily increased in recent years, and there is interest in developing the site as a permanent tourist attraction. However, if startled or harassed this species is capable of inflicting a serious, even fatal wound with its sting. The sting can measure over 30 cm (11.8 in) long and penetrate most types of footwear, including kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
bootee
Wetsuit boot
In water sports a bootee, bootie, or wetsuit boot is a thick sock-like garment made of wetsuit material. They serve the dual purpose of protecting the diver's feet when walking out of water, with or without a wetsuit, and keeping their feet warm underwater.-Thermal skin:In many water sports such as...
s; its mucous sheath contains a toxin
Toxin
A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...
that causes necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
. The most dangerous injuries involve damage to a vital organ, massive blood loss, and/or secondary septicemia or tetanus
Tetanus
Tetanus is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, rod-shaped, obligate anaerobic bacterium Clostridium tetani...
. There have been cases where a startled ray had jumped out of the water and pierced a wader's chest cavity. This species is responsible for the majority of stingray injuries off New Zealand.
Throughout its range, the short-tail stingray is caught incidentally
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
by various commercial fisheries
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
using trawls, Danish and purse seines, longlines and set lines, and drag and set nets
Fishing net
A fishing net or fishnet is a net that is used for fishing. Fishing nets are meshes usually formed by knotting a relatively thin thread. Modern nets are usually made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and...
. It is also caught by recreational fishers
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
using hook-and-line (from boats or the shore), spears, and harpoon
Harpoon
A harpoon is a long spear-like instrument used in fishing to catch fish or large marine mammals such as whales. It accomplishes this task by impaling the target animal, allowing the fishermen to use a rope or chain attached to the butt of the projectile to catch the animal...
s. Most individuals caught are released alive; often fishers cut off their tails beforehand for safety, though this practice does not seem to have a significant impact on the rays' long-term survival. Sport fishers occasionally keep captured rays for meat or angling competitions; a small number are also kept for display in public aquarium
Public aquarium
A public aquarium is the aquatic counterpart of a zoo, housing living aquatic species for viewing. Most public aquariums feature tanks larger than those kept by home aquarists, as well as smaller tanks. Since the first public aquariums were built in the mid-19th century, they have become popular...
s, and it has reproduced in captivity. As it survives fishing activities well and remains common throughout its range, the International Union for Conservation of Nature (IUCN) has assessed the short-tail stingray as Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
. Within most of this species' range off New Zealand, targeting it commercially is prohibited.