Spade-toothed whale (Mesoplodon traversii)

In brief

The spade-toothed whale (Mesoplodon traversii) is the rarest and most poorly known cetacean in the world: only seven individuals have been recorded in a century and a half, six in New Zealand and one in Chile, and the species has never been observed at sea. The dissection of a 5 m male stranded in Otago in July 2024 yielded the very first complete anatomical data.

Identification

With an estimated length of 5 to 5.5 m in adults, the spade-toothed whale has the streamlined outline typical of the genus Mesoplodon: a spindle-shaped body, a small head extended by a moderately long beak, short flippers and a triangular dorsal fin with a concave trailing edge, set about two thirds of the way back along the body. The rostrum is relatively broad compared with that of the other mesoplodont beaked whales. The coloration, described from the two animals stranded in 2010, combines a dark grey to black back with a white belly, separated by an oblique pale band that runs up from behind the eye towards the dorsal fin and forms a pale thoracic patch; the area around the eye, the beak and the flippers are dark. The measured female was 5.3 m long and her male calf 3.5 m; the only adult male examined to date, stranded in Otago in July 2024, measured 5 m.

The diagnostic character lies in the teeth. As in all mesoplodont beaked whales, only adult males develop a pair of functional teeth, set in the middle of the lower jaw and protruding from the mouth. In this species they are massive, of the order of 23 cm, and distinctly broader than those of the strap-toothed whale, with a prominent denticle at the tip. The exposed portion recalls the blade of the flensing spades handled by nineteenth-century whalers, hence the name spade-toothed whale. The 2024 dissection also revealed tiny vestigial teeth embedded in the gum of the upper jaw, a valuable clue to the evolutionary history of the group.

Misidentification is the rule here rather than the exception. The two animals stranded at Opape in 2010 were first assigned to Gray's beaked whale (Mesoplodon grayi), a common species in New Zealand, and only a DNA analysis revealed their true identity. The shape of the teeth superficially brings the species close to the strap-toothed whale (M. layardii), of which it is nevertheless not a close relative, while its skull recalls that of the ginkgo-toothed beaked whale (M. ginkgodens), on a markedly larger scale. In practice, apart from an adult male with erupted teeth, only genetics allows a reliable identification.

Taxonomy

Described by the British zoologist John Edward Gray in 1874 under the name Dolichodon traversii, the species originally rested on a lower jaw bearing its teeth, collected in 1872 by the naturalist Henry Hammersley Travers on Pitt Island, in the Chatham Islands (New Zealand), a type locality lying at 44°17' S and 176°15' W. The epithet traversii honours its collector.

It belongs to the genus Mesoplodon, the most species-rich of all cetacean genera, within the beaked whale family, treated as Ziphiidae in most current reference works, including the World Register of Marine Species, and as Hyperoodontidae in some classifications. A calvarium collected in 1986 on Robinson Crusoe Island (Juan Fernández Islands, Chile) had been described as a distinct species, Mesoplodon bahamondi, before being referred to M. traversii; that name is now a synonym. The exact phylogenetic position of the species within the genus remains uncertain, the available molecular data still being contradictory.

Distribution and habitat

Seven records in a century and a half: that is all science has to work with. The first is the jaw from Pitt Island (1872); then come a calvarium found in the 1950s on Whakaari/White Island, in New Zealand, the Chilean calvarium from Robinson Crusoe Island (1986), the female and her calf stranded in December 2010 on Opape beach, in the Bay of Plenty, an individual stranded in 2017 at Waipiro Bay, north of Gisborne, identified by DNA analysis but buried on the spot before any dissection because of the extreme isolation of the site, so that neither its sex nor its length was published, and finally the 5 m male found on 4 July 2024 at the mouth of the Taiari (Taieri Mouth), in Otago.

Six of these seven records therefore come from New Zealand, only one from Chile. The species is presumed to be strictly confined to the Southern Hemisphere, and in all likelihood to the South Pacific alone, where it is thought to frequent deep offshore waters like the other mesoplodont beaked whales. New Zealand is a global hotspot for beaked whales: thirteen of the twenty-four known species are recorded there and seven were first described there from stranded animals.

There is no record from French waters, neither in the Mediterranean, nor in the Bay of Biscay, nor in the English Channel, nor overseas. The French territories of the South Pacific lie within a geographical area theoretically compatible with its range, but no data document its presence there.

Biology and ecology

Almost everything that can be said about the biology of this whale rests on inference, for want of observation at sea. The examination of the 2024 male, carried out from 2 to 6 December at the AgResearch centre at Invermay, has nevertheless yielded the first direct elements.

Feeding: the stomach contained squid beaks and eye lenses, confirming a diet dominated by cephalopods, to which small fish are probably added; it also held parasitic worms and fragments of unidentified organisms. The dissection revealed nine stomach compartments, a count until then unknown for the species, as well as anatomical structures associated with prey capture and sound production.

Diving: no direct data exist for this species, but beaked whales are among the most extreme divers in the living world: in Cuvier's beaked whale (Ziphius cavirostris), a dive to 2,992 m and a breath-hold of 222 minutes have been recorded.

Social life: the few indications available suggest that the species lives alone or in small groups, like most mesoplodont beaked whales.

Breeding and longevity: no quantitative data. The presence, in 2010, of a 3.5 m juvenile male alongside a 5.3 m female attests at least to a prolonged period of maternal care. Neither gestation length, nor age at maturity, nor longevity is documented.

Status and conservation

The spade-toothed whale is listed as “Data Deficient” (DD) on the IUCN Red List. The most recent assessment, published in December 2020 as part of a review covering twenty-two cetaceans, maintained this status unchanged, even as the majority of beaked whales moved to “Least Concern“: knowledge is so fragmentary that no category, from “Least Concern” to “Critically Endangered”, can be ruled out. Neither the population size nor its trend is known.

The threats identified are those bearing on beaked whales as a whole: noise pollution of human origin, in particular active military sonar and seismic survey campaigns, to which this group is notoriously sensitive; bycatch and entanglement in fishing gear; plastic ingestion; and, over a longer term, the effects of climate change and ocean acidification on invertebrate prey.

The species has been listed in Appendix II of CITES since 13 February 2003 and falls under the CMS Memorandum of Understanding for the Conservation of Cetaceans and their Habitats in the Pacific Islands Region. In New Zealand, its monitoring is the responsibility of the Department of Conservation, for which every stranding is a major scientific event.

Observing this species

No sighting at sea has ever been confirmed: the species is known only from strandings, some of them animals still alive that died shortly after coming ashore (Opape in 2010, Waipiro Bay in 2017), and none was identified at the time. It is to date the only large whale whose appearance and behaviour at sea remain entirely unknown. No whale-watching trip, anywhere in the world, offers a reasonable prospect of encountering it, and an animal glimpsed offshore would in any case remain unidentifiable without a genetic sample.

The useful contribution therefore comes through strandings. Faced with a stranded cetacean, dead or alive, the rule is not to touch it, to take no sample and cut nothing, to keep dogs at a distance and to alert the competent network immediately: the Department of Conservation in New Zealand, the Réseau national échouages coordinated by the Observatoire Pelagis in France. Photographs of the head, the teeth and the colour pattern, together with a GPS position, are of considerable scientific value.

The cultural dimension counts just as much. In New Zealand, whales are taonga (treasures) for Māori: the dissection of December 2024 was conducted under the authority of Te Rūnanga o Ōtākou, which gave the animal the name Ōnumia, with the participation of young people from the hapū guided by experts from Ngāti Wai. The skeleton will go to the Tūhura Otago Museum, fitted with a 3D-printed jaw, the original mandible being kept by the rūnanga.

Frequently asked questions

How many spade-toothed whales are known?

Seven, recorded between 1872 and 2024: six in New Zealand and one in Chile. Several of them are known only from bones (one jaw, two calvaria).

Has this whale ever been observed at sea?

No. No sighting at sea has ever been confirmed: the species is known only from strandings, some of them animals still alive that died shortly afterwards (Opape in 2010, Waipiro Bay in 2017), none of which was identified at the time. Its appearance and behaviour at sea remain entirely unknown, which makes it the least known large whale on the planet.

What does the discovery of nine stomach compartments mean?

The dissection of December 2024 made it possible, for the first time, to count the stomach compartments of the species: nine, some of them containing squid beaks and eye lenses. A compartmented stomach is common in toothed whales, but the exact count remained unknown for this species.

Can it be encountered in French waters?

No. The seven known records all come from the South Pacific. The species has never been reported in the Mediterranean, in the Bay of Biscay, in the English Channel, or in French overseas waters.

Why is it listed as “Data Deficient” rather than “Endangered”?

Because nothing allows its population size or its trend to be estimated. The IUCN reserves this category for species in which every category, from “Least Concern” to “Critically Endangered“, remains plausible. This status was confirmed in December 2020.

How can it be told apart from Gray's beaked whale?

With difficulty. The two animals stranded at Opape in 2010 were first identified as Gray's beaked whales; only the DNA analysis revealed that they belonged to Mesoplodon traversii. In an adult male, the massive, broad teeth of the lower jaw are a clue, but the confirmation remains genetic.

Sources

• https://en.wikipedia.org/wiki/Spade-toothed_whale
• https://fr.wikipedia.org/wiki/Baleine_%C3%A0_bec_de_Travers
• https://iucn-csg.org/22-updated-cetacean-red-list-assessments-published-in-december-2020/
• https://www.doc.govt.nz/news/media-releases/2024-media-releases/spade-toothed-whale-reveals-new-discoveries/
• https://www.doc.govt.nz/nature/native-animals/marine-mammals/whales/beaked-whales/
• https://www.marinespecies.org/aphia.php?p=taxdetails&id=254993
• https://us.whales.org/spade-toothed-beaked-whale/
• https://au.whales.org/whales-dolphins/species-guide/spade-toothed-beaked-whale/
• https://news.mongabay.com/2024/12/scientists-maori-experts-uncover-new-insights-into-rare-spade-toothed-whale/
• https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0092633
• https://www.theguardian.com/world/article/2024/jul/16/worlds-rarest-whale-spade-toothed-new-zealand

Profile compiled from authoritative scientific sources (IUCN, NOAA Fisheries, specialist literature) and reviewed for factual accuracy.