Spade-toothed whale

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Spade-toothed whale
Spade-toothedWhale.jpg
A beached male of the species found in New Zealand in 2024
CITES Appendix II (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Ziphiidae
Genus: Mesoplodon
Species:
M. traversii
Binomial name
Mesoplodon traversii
(Gray, 1874)
Mesoplodon traversii distribution.png
Locations and dates of specimens
Synonyms

Dolichodon traversiiGray, 1874
Mesoplodon bahamondiReyes, Van Waerebeek, Cárdenas and Yáñez, 1995

Contents

The spade-toothed whale (Mesoplodon traversii) is the rarest species of beaked whale. As of a find in2024, only six specimens have been confirmed, all in the South Pacific, five in New Zealand and one in Chile. Very little is known about the species.

Discovery

Lower jaw found on Pitt Island in 1872. Illustration by "J.B." (John Buchanan) published in Hector 1873 Mesoplodon traversii TPRSNZ1872-5.2.6.1.19-a14-700w.jpg
Lower jaw found on Pitt Island in 1872. Illustration by "J.B." (John Buchanan) published in Hector 1873

The whale was discovered from a lower jaw with teeth found by naturalist Henry Travers on Pitt Island in the Chatham Islands of New Zealand in 1872. James Hector, the director of the Colonial Museum, reported the jaw in an 1873 paper on the whales and dolphins of New Zealand, thinking it a specimen of strap-toothed whale (Dolichodon layardii), which had been described by British Museum zoologist John Edward Gray in 1865 from a South African specimen. [3] Gray, in an 1874 response, doubted Hector's identification and thought the jaw likely from a new species, which he provisionally named Dolichodon traversii in honor of Travers, the collector. [4] Hector was not persuaded though and insisted in an 1878 article that it was the jaw of a strap-toothed whale, which by then had been renamed Mesoplodon layardi. [5] [6]

A damaged calvaria (the top of the skull) was found washed up on Robinson Crusoe Island, Chile, in 1993 and was described as a new species, Mesoplodon bahamondi or Bahamonde's beaked whale. [7] A calvaria found at White Island in New Zealand in the 1950s went unidentified for about 40 years, until in 1999 it was identified as being from a ginkgo-toothed beaked whale (Mesoplodon ginkgodens). [8] According to a 2002 study, DNA sequence and morphological comparisons show that the first three finds all came from the same species, which is therefore properly known as M. traversii. [6]

In December 2010, a 5.3-metre (17 ft) cow and 3.5-metre (11 ft) male calf stranded, then died, on Opape Beach, eastern Bay of Plenty, New Zealand. At the time they were thought to be Gray's beaked whale (Mesoplodon grayi), and were buried at the beach after photographs, measurements and tissue samples were taken. Genetic analysis in 2011 revealed that they were spade-toothed whales, the first whole individuals known to have been seen. The skeletons were exhumed, without the female's skull, which had washed out to sea, and were taken to Te Papa, New Zealand's national museum. The first ever description of the external appearance of the whale, along with an analysis of DNA, was published in 2012. [9] [10] [11] [12]

On 4 July 2024, a dead 5-metre (16 ft) male blackish-silver specimen washed ashore near Taieri Mouth, on the southern east coast of the South Island, New Zealand. [13] Samples from the intact specimen were taken by the Department of Conservation and sent to the University of Auckland's Cetacean Tissue Archive for DNA testing. [14] The specimen was brought to the Invermay Agricultural Centre in Mosgiel for dissection, which began on 2 December. This was the first intact specimen able to be dissected. [15]

Description

Size comparison to an average human Mesoplodon traversii.svg
Size comparison to an average human
Skeleton Mesoplodon traversii.jpg
Skeleton

Until 2012, nothing was known about this species other than cranial and dental anatomy. Some differences exist between it and other mesoplodonts, such as the relatively large width of the rostrum. Its appearance might be most similar to an oversized ginkgo-toothed beaked whale in overall shape, as their skulls are quite alike except in size. The distinguishing characters are the very large teeth, 23 cm (9 in), close in size to those of the strap-toothed whale. The teeth are much wider than those of the strap-toothed, and a peculiar denticle on the tip of the teeth present on both species is much more pronounced in the spade-toothed whale. It is believed that only the males obtain the jutted denticle and that it smoothens over time due to aggressive behavior with other males. [16] The common name was chosen because the part of the tooth that protrudes from the gums (unlike the strap-like teeth of strap-toothed whales) has a shape similar to the tip of a flensing spade as used by 19th-century whalers.

Despite the rather similar dentition, the spade-toothed whale and strap-toothed whale seem to be only distantly related. The present species' relationships are not known with certainty, though, because this species is very distinct morphologically, and the DNA sequence information is contradictory and is currently not good enough to support a robust phylogenetic hypothesis. [6] [17] Judging from the size of the skull, the species was thought to be between 5.0 and 5.5 m (16.4 and 18.0 ft) in length, perhaps a bit larger. The first (2010) known complete specimens are a 5.3-m (17.4-ft) adult female and her 3.5-m (11.5-ft) male calf. The cow was spindle-shaped, with a triangular dorsal fin with a concave trailing edge set about two-thirds the way back. It was dark gray or black dorsally and white ventrally, with a light thoracic patch created by a diagonal band that extends from behind the eye downwards and back to the dorsal fin. It also has a dark eye patch, rostrum, and flippers. [11]

Behaviour and ecology

It is likely the most poorly known large mammal species of modern times. It has never been seen alive, so nothing is known of its behavior. It is presumably similar to other medium-sized Mesoplodon , which are typically deep-water species living alone or in small groups and feeding on cephalopods and small fish. Following a year-long gestation period, the young probably become independent of their mothers at about one year of age, as is the case in most whales, with roughly a 73% chance of survival past year one. [18]

It is assumed that the remaining population lives solely in the Southern Hemisphere, and possibly only in the South Pacific. [19]

Conservation

The population status of the spade-toothed whale is entirely unknown.

The spade-toothed whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU). [20] The species' IUCN Red List conservation status is "Data Deficient (DD)" [21] due to lack of information and uncertain data. [22]

Specimens

The sex of the two 20th-century specimens is unknown. The sex could in theory be determined by recovering or failing to recover DNA sequences of the Y chromosome.

See also

Related Research Articles

<span class="mw-page-title-main">Beaked whale</span> Family of mammals

Beaked whales are a family of cetaceans noted as being one of the least-known groups of mammals because of their deep-sea habitat, reclusive behavior and apparent low abundance. Only three or four of the 24 existing species are reasonably well-known. Baird's beaked whales and Cuvier's beaked whales were subject to commercial exploitation, off the coast of Japan, while the northern bottlenose whale was extensively hunted in the northern part of the North Atlantic in the late 19th and early 20th centuries.

<span class="mw-page-title-main">Andrews' beaked whale</span> Species of mammal

Andrews' beaked whale, sometimes known as the deep-crest beaked whale or splay-toothed whale, is one of the least known members of a poorly known genus. The species has never been observed in the wild, and is known only from specimens washed up on beaches.

<i>Mesoplodon</i> Genus of beaked whales

Mesoplodont whales are 16 species of toothed whale in the genus Mesoplodon, making it the largest genus in the cetacean order. Two species were described as recently as 1991 and 2002, and marine biologists predict the discovery of more species in the future. A new species was described in 2021. They are the most poorly known group of large mammals. The generic name "mesoplodon" comes from the Greek meso- (middle) - hopla (arms) - odon (teeth), and may be translated as 'armed with a tooth in the centre of the jaw'.

<span class="mw-page-title-main">Hubbs' beaked whale</span> Species of mammal

Hubbs' beaked whale was initially thought to be an Andrews' beaked whale when discovered by ichthyologist Carl Hubbs; however, it was named in his honor when it was discovered to be a new species. This species has the typical dentition found in the genus, but its main outstanding features are a white "cap" on the head and very extensive scarring. The species is known from 31 strandings, a few at-sea sightings, and observations of two stranded whales that were kept in captivity for 16–25 days.

<span class="mw-page-title-main">Blainville's beaked whale</span> Species of mammal

Blainville's beaked whale, or the dense-beaked whale, is believed to be the widest ranging mesoplodont whale. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw — the heaviest bone he had ever come across — which resulted in the name densirostris. Off the northeastern Bahamas, the animals are particularly well documented, and a photo identification project started sometime after 2002.

<span class="mw-page-title-main">Gervais's beaked whale</span> Species of whale

Gervais's beaked whale, sometimes known as the Antillean beaked whale, Gulf Stream beaked whale, or European beaked whale is the most frequently stranding type of mesoplodont whale off the coast of North America. It has also stranded off South America and Africa.

<span class="mw-page-title-main">Ginkgo-toothed beaked whale</span> Species of mammal

The ginkgo-toothed beaked whale is a poorly known species of whale even for a beaked whale, and was named for the unusual shape of its dual teeth. It is a fairly typical-looking species, but is notable for the males not having any scarring.

<span class="mw-page-title-main">Gray's beaked whale</span> Species of mammal

Gray's beaked whale, sometimes known as Haast's beaked whale, the scamperdown whale, or the southern beaked whale, is one of the better-known members of the genus Mesoplodon. This species is fairly gregarious and strands relatively frequently for a beaked whale. In the Māori language, this species is called hakurā or iheihe.

<span class="mw-page-title-main">Hector's beaked whale</span> Species of mammal

Hector's beaked whale, is a small mesoplodont living in the Southern Hemisphere. This whale is named after Sir James Hector, a founder of the colonial museum in Wellington, New Zealand. The species has rarely been seen in the wild.

<span class="mw-page-title-main">Strap-toothed whale</span> Species of whale

The strap-toothed beaked whale, also known as Layard's beaked whale, is one of the largest members of the Mesoplodon genus, growing to 6.2 m (20 ft) in length and reaching up to 1,300 kg (2,900 lb). The common and scientific name was given in honor of Edgar Leopold Layard, the curator of the South African Museum, who prepared drawings of a skull and sent them to the British taxonomist John Edward Gray, who described the species in 1865.

<span class="mw-page-title-main">True's beaked whale</span> Species of mammal

True's beaked whale is a medium-sized whale in the genus Mesoplodon. It is native to the northern Atlantic Ocean. The common name is in reference to Frederick W. True, a curator at the United States National Museum.

<span class="mw-page-title-main">Tropical bottlenose whale</span> Species of mammal

The tropical bottlenose whale, also known as the Indo-Pacific beaked whale or Longman's beaked whale, was considered to be the world's rarest cetacean until recently, but the spade-toothed whale now holds that position. As of 2010, the species is now known from nearly a dozen strandings and over 65 sightings. This is the only species in the genus Indopacetus.

<span class="mw-page-title-main">Pygmy beaked whale</span> Species of mammal

The pygmy beaked whale, also known as the bandolero beaked whale, Peruvian beaked whale and lesser beaked whale, is the smallest of the mesoplodonts and one of the newest discoveries. There were at least two dozen sightings of an unknown beaked whale named Mesoplodon sp. A before the initial classification, and those are now believed to be synonymous with the species. The species was formally described in 1991, based on ten specimens obtained from Peru between 1976 and 1989, including a 3.72 m (12.2 ft) adult male as the type specimen. A specimen that stranded at Paracas, Peru in 1955 has since been identified as a pygmy beaked whale. Since 1987, there have been an additional 40 sightings of the species, for a total of 65.

<span class="mw-page-title-main">Stejneger's beaked whale</span> Species of mammal

Stejneger's beaked whale, also known as the Bering Sea beaked whale or the saber-toothed whale, is a relatively unknown member of the genus Mesoplodon inhabiting the North Pacific Ocean. Leonhard Hess Stejneger collected the type specimen on Bering Island in 1883, from which Frederick W. True provided the species' description in 1885. In 1904, the first complete skull was collected, which confirmed the species' validity. The most noteworthy characteristic of the males is the very large, saber-like teeth, hence the name.

<span class="mw-page-title-main">Arnoux's beaked whale</span> Species of whale

Arnoux's beaked whale, also called the southern four-toothed whale, southern beaked whale, New Zealand beaked whale, southern giant bottlenose whale and southern porpoise whale is one of the species of Berardius. Arnoux's and Baird's beaked whales are so similar that researchers debated whether or not they are simply two populations of the same species, until genetic evidence and their wide geographical separation led them to be classified as separate. Little is known about their behavior due to infrequent encounters with live individuals.

<span class="mw-page-title-main">Perrin's beaked whale</span> Species of mammal

Perrin's beaked whale is part of the toothed whale suborder and is one of over 90 known cetaceans in existence today. Beaked whales are part of the family Ziphiidae, which are the second most diverse group out of all marine mammals with over 20 species currently recognized. Although diverse, little is understood about these timid, deep divers that can dive for up to two hours. The whales are partially named after their beak shaped jaw, which extends from their small head. The genus name Mesoplodon comes from the Greek meanings of meso- (middle), - hopla (arms), - odon (teeth), and may be translated as 'armed with a tooth in the center of the jaw'.

<span class="mw-page-title-main">Southern bottlenose whale</span> Species of mammal

The southern bottlenose whale is a species of whale, in the ziphiid family, one of two members of the genus Hyperoodon. Seldom observed, the southern bottlenose whale is resident in Antarctic waters. The species was first described by English zoologist William Henry Flower in 1882, based on a water-worn skull from Lewis Island, in the Dampier Archipelago, Western Australia. They live in deep ocean waters over 1000 meters.

Deraniyagala's beaked whale is a species of mesoplodont whale closely related to the ginkgo-toothed beaked whale.

References

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