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Abstract
Nineteen occurrences of interspecific sexual behavior between male southern sea otters (Enhydra lutris nereis) and juvenile Pacific harbor seals (Phoca vitulina richardsi) were reported in Monterey Bay, California, between 2000 and 2002. At least three different male sea otters were observed harassing, dragging, guarding, and copulating with harbor seals for up to 7 d postmortem. Carcasses of 15 juvenile harbor seals were recovered, and seven were necropsied in detail by a veterinary pathologist. Necropsy findings from two female sea otters that were recovered dead from male sea otters exhibiting similar behavior are also presented to facilitate a comparison of lesions. The most frequent lesions included superficial skin lacerations; hemorrhage around the nose, eyes, flippers, and perineum; and traumatic corneal erosions or ulcers. The harbor seals sustained severe genital trauma, ranging from vaginal perforation to vagino-cervical transection, and colorectal perforations as a result of penile penetration. One harbor seal developed severe pneumoperitoneum subsequent to vaginal perforation, which was also observed in both female sea otters and has been reported as a postcoital lesion in humans. This study represents the first description of lesions resulting from forced copulation of harbor seals by sea otters and is also the first report of pneumoperitoneum secondary to forced copulation in a nonhuman animal. Possible explanations for this behavior are discussed in the context of sea otter biology and population demographics.
Key Words: sea otter, Enhydra lutris nereis, harbor seal, Phoca vitulina richardsi, forced copulation, interspecific sexual behavior, mating trauma, pneumoperitoneum
Introduction
Sexual interactions between species have been well-documented among marine mammals (Wilson, 1975; Best et al., 1981; Harcourt, 1993; Hatfield et al., 1994; Miller et al., 1996; Mortenson & Follis, 1997; Cassini, 1998; Hayward, 2003). Such behavior has occasionally been observed among pinnipeds with overlapping breeding seasons that share the same rookeries, providing ample opportunities for interaction between adult or subadult males and heterospecific females (Miller et al., 1996). Documentation of hybrid offspring within mixed colonies of otariids (Miller et al., 1996) and phocids (Kovacs et al., 1997) further supports the occurrence of breeding events between pinniped species.
Reports also exist of interspecific sexual interactions occurring outside of the normal breeding season in which a single aggressive male opportunistically copulated with females or pups during periods when conspecific...