Mesoplodon perrini

Perrin's beaked whale (Mesoplodon perrini) is the newest species of beaked whale to be described. The first two specimens were found in May 1975 stranded on the California coast, with two more specimens being found in 1978 and 1979, one in September 1997 and one in October 2013. On May 31, 2019, a juvenile male Perrin's beaked whale stranded alive near Santa Cruz, California, and was subsequently euthanized . The first four individuals were initially identified as Hector's beaked whale (Mesoplodon hectori), while the fifth was assumed to be a neonate Cuvier's beaked whale. Following inclusion of one of these specimens in a mtDNA sequence database of beaked whales, it turned out that they seemed well distinct from M. hectori (Dalebout et al. 1998). The other 'Hector's' specimens from California were subsequently confirmed to belong to the same undescribed taxon (Dalebout 2002). The new species was formally described in 2002 by Dalebout et al.; its common and specific names are a tribute to cetologist William F. Perrin. Despite the superficial similarities to the (entirely allopatric) Hector's beaked whale, this species is closely related to the pygmy beaked whale, the next most-recently described species, and probably represents its Northern Hemisphere sister species. Perrin's beaked whale has not definitely been recorded alive by scientists. However, its appearance is known from the beached specimens, and following resolution of their identity as a new species, it seems highly likely the four supposed Hector's beaked whales, which were seen off California in 1976 and 1978 (both involving two individuals), were actually this species (Mead 1981, Dalebout et al. 2002). Perrin's beaked whales cannot be identified with absolute certainty at sea. However, the combination of small size, appearance and presumed range makes a confusion unlikely. Stranded specimens can be identified as this species by either DNA sequence data and/or anatomical details of the skull.(Dalebout et al. 2002) This species has a fairly typical body shape for a mesoplodont, with a small head, long body, and deep tail. The rostrum of this whale is shorter than every other mesoplodont other than Hector's and the pygmy beaked whales, especially in young individuals. The mouthline of this species is straight, and the melon forms a small bulge with a crescent-shaped blowhole with forward-pointing tips. The teeth on this species are fairly large and towards the tip of the mouth. Throat grooves are present on this species. The mature male specimen was 3.9 metres in length (13 feet) and the female was 4.4 metres (14 feet 8 inches) in length; the immature males measured between 2.1 and 2.45 metres (7-7.5 ft). The coloration is dark gray above and white below in the holotype male, with a lighter gray underside of the tail fluke. A white patch is present near the navel. The colouration of females is not known, since the only specimen was rather decomposed. Calves are light to dark gray on top, and white below, including the lower jaw and throat; the underside of the flukes is lighter gray. There is a dark 'mask' on the head, from the corners of the mouth to the eye region, the rostrum, and the melon, and there are white stripes on the tail underside. The adult male had the typical white scar-stripes from fights with conspecifics. Only adult males seem to have teeth, and even these only two, in line with other Mesoplodon species. In Perrin's beaked whale, the teeth are located near the tip of the lower jaw and are roughly equilateral triangles when viewed laterally and still placed in the jaw; in this they resemble the foreteeth of Baird's beaked whale more than those of the Mesoplodon species which are otherwise similar.(Dalebout et al. 2002)