Перриннің тұмсықты киті (Mesoplodon perrini) сипаттамасы

Species of mammal

Perrin's beaked whale (Mesoplodon perrini) 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'. Perrin's beaked whale was described as a new species in 2002 by Dalebout et al. based on five animals stranding on the coast of California between 1975 and 1997, which were initially identified as other species. The common and specific names of Mesopledon perrini are a tribute to cetologist William F. Perrin. As of May 2019, only six specimens have ever been examined. The first four individuals were initially identified as Hector's beaked whales (Mesoplodon hectori), but the mtDNA sequence database of beaked whales revealed the specimens were genetically distinct. The fifth was assumed to be a neonate Cuvier's beaked whale (Ziphius cavirostris).

Perrin's beaked whales are closely related to pygmy beaked whales and likely represent pygmy beaked whales' Northern Hemisphere sister species. Perrin's beaked whales have not definitively been recorded alive by scientists; however, its appearance is known from beached specimens. Perrin's beaked whales cannot be identified with absolute certainty at sea. However, the combination of small size, appearance, and a small presumed geographical range makes uncertainty unlikely. Stranded specimens can be identified as this species by either DNA sequence data and/or anatomical details of the skull. In Perrin's beaked whale, the teeth are located near the tip of the lower jaw and are roughly equilateral triangles when viewed laterally (from the side) in the jaw, which resembles the font teeth of Baird's beaked whale (Berardius bairdii) more than other Mesoplodon species. Most of the characteristics that set M. perrini apart from related species are molecular. Substantial differences in mtDNA and cytochrome b form the basis for its diagnosis as a new species. Morphological similarities suggested that the closest relative of M. perrini was M. hectori. However, based on the molecular characters, Dalebout et al. concluded that its true sister species is M. peruvianus.

Currently (2019), Perrin's beaked whales have only been found near North Pacific waters off the coast of central and southern California. Stranded Perrin's beaked whales have been found along the Californian coast between Torrey Pines State Reserve, just north of San Diego (32°55’N, 117°15’W) and Fisherman's Wharf, Monterey (36°37’N, 121°55’W). but the occurrence of such scars on cetaceans is not. This suggests either these cetaceans are migratory and pass through the territory of Isistius spp., or the distribution of Isistius spp. extends farther north in deeper waters and attack cetaceans when they dive. The habitat preferences of other beaked whales suggest M. perrini can primarily be found in oceanic waters that are over 1,000 m in depth.

Beaked whales are timid, deep divers who can dive for up to 2 hours, so little is known about the behavior and ecology of Perrin's beaked whales because they are rarely seen. Again, Perrin's beaked whales have not definitely been recorded alive by scientists, so the limited information known about the species is derived from dead individuals that are beached. Some information is assumed based on the shared adaptations and behaviors of the species within the genus Mesoplodon.

Based on the stomach contents of stranded whales, these whales primarily feed on pelagic squid, such as Octopoteuthis deletron; found within the remains of the female's stomach. Single scar lines could suggest they were created by glancing blows rather than direct attacks.

The largest Perrin's beaked whale calf, LACM 088901, at 2.45 m of length, appeared to be independent from its mother. The smallest specimen, USNM 504259, at 2.1 m of length, had a fringed tongue which indicated it was still suckling. Within a passive acoustics study, signals of BW43 were only detected in southern California at deep sites (1100–1300 m) and are thought to be produced by Perrin's beaked whale, known only from Californian waters.

Data suggests a significant decline in abundance for Mesoplodon spp. in the California Current between 1996 and 2001. Declines are hypothesized to have occurred from the effects of incidental mortality from fishing, impacts of anthropogenic noise (Navy sonar), and ecosystem changes. Since then, the population size of Mesoplodon beaked whales has increased from a mean of 1230 in 2001 to 3439 in 2014 within California Current waters off the U. S. West Coast.

Perrin's beaked whales are threatened by attacks from sharks such as the cookiecutter shark (Isistius brasiliensis). As with their relatives, cookiecutter sharks attack this whale with attempts at biting off chunks of flesh. Such attacks are generally not life threatening to the whale. It is a host of the thoracican barnacle Conchoderma auritum, and for one or several species of parasitic Phyllobothrium cestodes (possibly Phyllobothrium delphini), this species is either a primary or a dead end host. These whales are vulnerable to naval sonar and seismic activity. Currently, there are no whaling threats for this species. Although Mesoplodon whales were never harvested commercially, there have been reports of them being taken by humans from time to time. Bycatch is likely one of the main threats to this deep water species due to it causing harm or death to whales entangled in fishing gear. According to the IUCN, this species has the potential to become caught in certain types of fishing gear, such as deepwater gill nets, used for capturing large pelagic fish species. Plastic is also seen as a threat to Perrin's beaked whales because it has been found within the stomach contents of stranded individuals.