intrasexual competition. The tusks may also help these whales distinguish individuals belonging to their species from those of similar, sympatric 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. This conclusion was later supported by analysis of nuclear actin sequences by Dalebout et al. (2004). Distribution and status 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). It is believed these whales inhabit the offshore waters of the Pacific coast of North America (and possibly elsewhere in the North Pacific) in waters 1,000 meters deep or more. However, the northern and southern limits of its range are entirely unknown. There is no current information on the home range and migratory behaviors of these whales, although biogeography of beaked whales suggests it does not reach the Equator. Even though current data suggest an eastern North Pacific distribution, there are too few records to date to draw any conclusions on this. Cookie-cutter shark scars on a calf found in Monterey could be evidence of migratory behavior, because in surface waters cookie-cutter sharks Isistius spp. are limited in their northern distribution, 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. Ecology and behavior 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