Biological Exuberance: Animal Homosexuality and Natural Diversity

Musk-ox (Reinhardt 1985:298). In Cattle Egrets, Fujioka and Yamagishi (1981:139) stated that males attempting homosexual copulations always rank higher than or equal to the males they mount. Yet two males in their study population who mounted other males were apparently not part of the dominance hierarchy (cf. their table 3), while the highest-ranking male did not participate in any same-sex mounts. M. Fujioka (personal communication) concedes that the rank of the males may not actually be an important factor in their homosexual mounting.

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Crested Black Macaque (Dixson 1977:77; Poirier 1964:96); American Bison (Reinhardt 1985:218, 222, 1987:8); Pig-tailed Macaque (Oi 1990a:350); Red Deer (Hall 1983:278); Pukeko (Jamieson and Craig 1987b:319-22); Japanese Macaque (Chapais and Mignault 1991:175-76); Bighorn Sheep (Shackleton 1991:179-80).

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A further argument is provided by “pile-up mounts,” i.e., when three individuals are all mounted (stacked) on each other. In this case, the mounter-mountee relations rarely if ever follow dominance lines: either they occur in species without dominance hierarchies (e.g., Sage Grouse, Common Murre), or else it is not the case that the middle animal is both higher-ranking than the animal it is mounting but lower-ranking than the animal who is mounting it (e.g., Wolf, Bonobo). For more on pile-up mounts, see chapter 4.

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Common Chimpanzee (Nishida and Hosaka 1996:122; Bygott 1974 [cited in Hanby 1974:845 (Japanese Macaque)]); White-faced Capuchin (Manson et al. 1997:771, 780); Blackbuck (Dubost and Feer 1981:89— 90); Cavies (Rood 1972:36); Gray-capped Social Weaver (Collias and Collias 1980:218, 220). Although mounting between male Musk-oxen in captivity seems to follow dominance lines (Reinhardt 1985), in wild herds Smith (1976) found no dominance hierarchy within (as opposed to between) sex/age classes. Same-sex mounting in the wild occurs among age-mates (who are therefore essentially equal in rank, e.g., two-year-old males mount each other).

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See, for example, Bertrand 1969:191 (Stumptail Macaque); Simonds 1965:183, Sugiyama 1971:259 (Bonnet Macaque); Bernstein 1972:406 (Pig-tailed Macaque); Dixson et al. 1975:195-96 (Talapoin Monkey); Kaufmann 1974:309 (Whiptail Wallaby).

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A distinction between consensual and nonconsensual homosexual mounts is found in more than 30 different species of mammals and birds. Direct evidence of sexual arousal and stimulation on the part of animals being mounted is also available in many species, including orgasmic (and other) responses in female Japanese, Rhesus, Stumptail, and Pig-tailed Macaques being mounted; erection and masturbation by male mountee Rhesus, Pig-tailed, and Crested Black Macaques; thrusting by male Bonobos being mounted; and stimulation of the mountee’s clitoris by her partner’s thrusting in Hanuman Langurs and Japanese Macaques. In addition to direct and indirect genital stimulation during mounting, it is quite likely that male animals being penetrated during anal intercourse also experience stimulation of the prostate gland (which presses against the wall of the rectum). In human males, direct stimulation of the prostate—for instance, during anal intercourse—can be highly arousing and may precipitate or enhance orgasm. A similar capacity is probably present in all male mammals. Although direct evidence (in the form of firsthand accounts) of the pleasurable or arousing nature of this activity is, of course, lacking in nonhuman animals, there is some indirect evidence. A standard technique of inducing erection and ejaculation (for purposes of artificial insemination) in male mammals is through anal and/or prostate stimulation. Known as electroejaculation, this technique involves insertion of an anal probe and stimulation of the rectum—especially in the area of the prostate gland—with a mild electrical current as well as back-and-forth (thrusting) movements of the probe. This technique has proven effective in numerous species of mammals, including virtually all of those in which male homosexual mounting and /or anal penetration occur. For further information on electroejaculation, see Watson, P. F., ed. (1978) Artificial Breeding of Non-Domestic Animals, Symposia of the Zoological Society of London no. 43, especially pp. 109, 129, 208—10, 221, 295 (London: Academic Press).

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