Sato’s beaked whale is a toothed whale species inhabiting the Sea of Okhotsk and other areas. Stranding Network Hokkaido, for whichMatsuishi Laboratory serves as the secretariat, has been collected specimens from beached bodies along the coast of the Sea of Okhotsk in Hokkaido since 2008, and in August 2019, it was registered as a new species.
New species Sato’s beaked whale Berardius minimus sp. nov. Yamada, Kitamura & Matsuishi, 2019
Illustration based on external morphometric measurements of a Sato’s beaked whale Picture : WATANABE Yoshimi, National Museum of Science
What is Sato's beaked whale?
It has been said among whaling experts in Hokkaido that the so-called "Tsuchi kujira"(Baird's beaked whale) has two types and a type is called "Kurotsuchi"(black Baird's beaked whale) or Karasu(Crow), which are darker and smaller in colour than regular Baird's beaked whales, but their true identity has not been clarified then.
The three black Baird's beaked whale collected in Hokkaido since 2008 by the cetacean research group "Stranding Network Hokkaido" (SNH), whose secretariat is theMatsuishi Lab. of Hokkaido University, had the characteristics of Baird's beaked whale genus, such as blow hole morphology, but their external morphology, including the head, was different from the previously known Baird's beaked whales.Kitamura et al. (2013) compared DNA sequences extracted from these three black Baird's beaked whales and 67 known Baird's beaked whales, which
were known in the literature. The results showed clear differences, raising the possibility of an unknown species of Baird's beaked whale that differs from the known species. Subsequently, Morin et al. (2017) reported that an unknown individual with a similar genetic composition also inhabits the Aleutian Islands. In order to describe this unknown species as a new species, it was necessary to understand its morphological characteristics and clarify its relationship to the two known species of the genus beaked whale (Arnoux'sbeaked whale and Baird's beaked whale) through comprehensive analysis.
In this study, SNH conducted morphological analyses of six individuals of unknown species collected by SNH. Four of these individuals were collected as whole-body skeletal specimens at the National Museum of Nature and Science, and their morphological characteristics were determined and multivariate analysis of the measurement results was conducted. The six individuals were shown to be different species from both well-known arnoux's beaked whale B. arnuxii and beaked whale B. bairdii.
Traditionally, morphological description is essential for species description, and osteological research, which is the basis of morphological description, requires a detailed understanding of the characteristics of known species and contrasting them with those of unknown species, which requires not only type specimens of known species, but also wading through numerous specimens to capture the characteristics of species, and to get a complete picture of the species as a whole. Dr. Tadasu Yamada, a research fellow emeritus at the National Museum of Nature and Science, and Dr. Tajima Yuko, a principal investigator, have carefully examined type specimens of Baird's beaked whales in the collections of the National Museum of Natural History (Paris), the United States Natural History Museum (the so-called Smithsonian Institution, Washington DC), and the National Museum of Natural History (Stockholm), and also conducted a survey of the collection at the Natural History Museum ( In addition, we also compared and examined specimens of Baird's beaked whales in the collections of the Natural History Museum (the so-called British Museum of Natural History, London), the Akatushun Museum (Ushuaia), and other museums.
Although the morphological distinction between B. bairdii and B. arnuxii is considered difficult, the skull of the unknown species examined in this study is clearly different from those two species, with unique proportions of each part and remarkable characteristics such as the shape of the plagiocephaly.
The mean body length of 34 known B. bairdii individuals in the Sea of Okhotsk was 10.0 m (Kishiro 2007), while the mean body length of mature males of this unknown species was 6.2-6.9 m. This is statistically significantly different, confirming the significantly smaller body size of this species.
Furthermore, principal component and discriminant analyses of cranial measurements of 10 individuals of B. bairdii, 7 individuals of B. arnuxii, and 4 individuals of unknown species confirmed that these three groups were clearly separated without overlap.
Furthermore, molecular phylogenetic analysis of the mitochondrial DNA control region (879-bp) of 7 B. bairdii and 2 B. arnuxii whales was conducted, as well as genetic information on 8 unknown species, including 3 specimens of unknown species newly obtained by SNH since 2014. bairdii , again confirming that the differences between the unknown species and the two known species are clearly greater than the genetic differences between B. arnuxii.
Based on the above results, we concluded that this unknown cetacean species should be added to the world's cetaceans as an independent species and described it as a new species, Berardius minimus as reported by Yamada et al. (2019).
In the world of taxonomy, species are recognized by their genus and species minor names (both in Latin, in principle). The genus name is Berardius, to which this species belongs, and the species minor name is "minimus," which means "smallest" in Latin, to indicate that this is the smallest species in the genus, at least for the present. The English name is Sato's beaked whale, after Ms Sato Haruko, a whale observer who contributed to the discovery and research of this species.
We intend to continue collecting information on beached Sato's beaked whales and collecting specimens to elucidate their distribution, migratory feeding habits, growth, maturity, and morphology.
Sato's beaked whale caught as bycatch in Shibetsu Town on July 20, 2004.
Photo by Kurasawa Minako
Source: Yamada et al. (2019)
A fresh Sato's beaked whale washed ashore on November 10, 2012 in Sarufutsu Village.
Photo: Sarufutsu Village Fishery Cooperative Association, Yasushi Shimizu Courtesy of Stranding Network Hokkaido
Source: Yamada et al. (2019)
References and websites
Yamada TK, Kitamura S, Abe S, Tajima Y,
Matsuda A, Mead JG, Matsuishi TF (2019) Description of a new species of beaked
found in the North Pacific. Scientific Reports https://doi.org/10.1038/s41598-019-46703-w
Kitamura S, Matsuishi
T, Yamada TK, Tajima Y, Ishikawa H, Tanabe S, Nakagawa H, Uni Y, Abe S
(2013) Two genetically distinct stocks in Baird's beaked whale (Cetacea:
Ziphiidae). Marine Mammal Science https://doi.org/10.1111/j.1748-7692.2012.00607.x
Morin PA., et al. (2016) Genetic
structure of the beaked whale genus Berardius in the North Pacific, with
genetic evidence for a new species. Marine Mammal Science 33 (2017):96-111. https://doi.org/10.1111/mms.12345