that are beached. Some information is assumed based on the shared adaptations and behaviors of the species within the genus Mesoplodon. Diet 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. Some unidentified vertebrate parts were also present. Assuming Perrin's beaked whales share the same diet as other beaked whales, they likely consume octopus and fish as well. Reproduction Little is known about the social structure, reproduction, age of sexual maturity, or lifespan of the Perrin's beaked whales, but scars on the bodies of males suggest aggressive competitive behavior. The two adult type specimens were both sexually mature and an analysis of the teeth indicated they were both about 9 years old. For this reason, it can be assumed that males reach sexual maturity around this age or sooner. The males of this species seem to engage in fights like most other mesoplodonts. Scars from fighting are present on this species, although the precise mechanism of combat is enigmatic: given the teeth's position near the lower jaw tips, it can be expected that the scars consist of two parallel lines. However, it is noted that the scars on the adult male appear to have been made with a single tooth, rather than with two teeth simultaneously, as might be expected in species with apical teeth. Single scar lines could suggest they were created by glancing blows rather than direct attacks. Development 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. Teeth were not present in the immature specimen [verification needed], but are not needed for feeding. The dates when the specimens were found suggest the young start to feed independently in summer. Considering most whales suckle until around age one; this suggests the young are born during the summer half of the year. Since all calves were similar in size, the calves were all estimated to be approximately one year old. Social/echolocation Perrin beaked whales are thought to produce a species-specific frequency modulated (FM) echolocation pulse of BW43. Within a passive acoustics study, signals of BW43 were only detected in southern California at deep sites (1100–1300 m) and are thought to