Shepherd's Beaked Whale
Shepherd's beaked whale (also known as the Tasman beaked whale; scientific name: Tasmacetus shepherdi) is one of 21 species of beaked whales (Hyperoodontidae or Ziphiidae), medium-sized whales with distinctive, long and narrow beaks and dorsal fins set far back on their bodies. They are marine mammals within the order of cetaceans.
It is a rare and poorly understood species. The IUCN notes that:
Shepherd's beaked whales are primarily known from a few dozen strandings, all south of 30°S, around New Zealand, southern Australia, southern South America, the Juan Fernandez Islands, and Tristan de Cunha (Mead 1989). There have been only a few sightings reported in the literature and the validity of most of those is suspect (or clearly erroneous. The confirmed sightings have been from south of Tasmania and in oceanic waters of the South Atlantic (Pitman et al. 2006). The majority of strandings have occurred in New Zealand. It is presumed that they have a circumpolar distribution in cold temperate waters of the Southern Hemisphere (MacLeod et al. 2006). It is possible that the species may be somewhat more widespread than the records suggest, since it was not likely to be accurately identified at sea until its recent re-description (Pitman et al. 2006).
The body of these whales is around six to seven meters in length. The head is small with a long, narrow beak. The dorsal fin is small and is located one third of the body length from the tail. The tail fluke is not notched, and the flippers are small and oval in shape. The back is uniform grayish-brown in color, fading to nearly white on the underbelly. Since very few of these whales have been seen while alive and body colors quickly darken following death, the true coloration of Shepherd's beaked whale is not known (Evans 1987, Tinker 1988).
Shepherd's beaked whale can be easily distinguished from other members of the family Ziphiidae by the presence of 17-29 conical teeth in both the upper and lower jaw. Males possess two additional teeth on the anterior most part of the lower jaw. These teeth, described as possessing "bulbous bases and conical crowns", are larger than the homodont cheek teeth, and are separated from the cheek teeth by a 4 cm diastema. One tooth sits on either side of the mandibular symphysis (Walker 1975, Evans 1987, Tinker 1988).
The blowhole is crescent in shape and is asymmetrically located on the left side of the top of the head. The eye sits directly below the blowhole. The first five vertebrae are fused and the first through seventh pairs of ribs possess two heads (Evans 1987, Tinker 1988). (Evans, 1987; Tinker, 1988; Walker, 1975) Overview physical features of the species are endothermic metabolism and bilateral symmetry.
Shepherd's beaked whale has rarely been seen alive and very little is known about its behavior. A key Behavior is motility.
Very little is currently known about the reproduction of this species. Key reproductive features are: gonochoric/gonochoristic/dioecious (sexes separate)
Distribution and Movements
Although the geographic range of this species is not clearly known, Tasmacetus shepherdi (Shepherd's beaked whale, Tasman whale) probably has a circumpolar distribution in temperate waters of the southern hemisphere. All known specimens have been found on beaches in New Zealand, Australia, Brazil, Tierra del Fuego, Argentina, Chile, and the Galapagos Islands (Evans 1987, Tinker 1988).
Based on stomach contents and locations where Tasmacetus shepherdi have washed ashore, this species is likely benthic and inhabits temperate waters of the Southern Hemisphere (Evans 1987, Tinker 1988).
These whales eat squid and various fishes, many of which are benthic, suggesting that Shepherd's beaked whale feeds at or near the sea floor (Tinker 1988). There is also evidence of predation upon mollusks.
Threats and Conservation Status
The IUCN lists Shepherd's beaked whale under the "insufficiently known" category (Simmonds and Hutchinson 1996). The IUCN Red List classifies this mammal as Data Deficient, while the US Federal List places the species as No special status. CITES also lists the taxon as: No special status.
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