Biological Exuberance: Animal Homosexuality and Natural Diversity

Hoyo, J., A. Elliott, and J. Sargatal, eds. [1996] Handbook of the Birds of the World, vol. 3: Hoatzin to Auks, p. 282. [Barcelona: Lynx Edicions]); Orang-utan (Galdikas 1981:286).

111

Walrus (Dittrich 1987:168); Musk-ox (Smith 1976:62); Bighorn Sheep (Hogg 1984:527; Geist 1971:139); Asiatic Mouflon (McClelland 1991:81); Grizzly Bear (Craighead et al. 1995:161); Olympic Marmot (Barash 1973:212); White-tailed Deer (Hirth 1977:43); Orang-utan (Galdikas 1981:286); White-faced Capuchin (Manson et al. 1997:775); Northern Fur Seal (Gentry 1998:172); Ruff (Hogan-Warburg 1966:167-68). Additionally, in one study of Matschie’s Tree Kangaroos—a species in which researchers deny that mounting between females is (homo) sexual (J. Steenberg, personal communication)—all mounts observed between animals of the opposite sex were “incomplete” in that they did not involve penetration or thrusting (Hutchins et al. 1991:158). Another study of the same population found both that “full” copulations between males and females were infrequent, and that in heterosexual contexts females showed few overt signs of sexual interest, since the behavioral cues for female sexual arousal are extremely subtle (Dabek 1994:84, 93—94, 116).

112

Morrill and Robertson 1990 (Tree Swallow); Scott, M. P., and T. N. Tan (1985) “A Radiotracer Technique for the Determination of Male Mating Success in Natural Populations,” Behavioral Ecology and Sociobiology 17:29-33. More recently, a copulation-verification technique using fluorescent powder has been tested for rodents. Dusted on males, the powder is transferred to females during mating and can be checked using ultraviolet light. Ironically, during the testing of this procedure, pairs of females were used as “controls” since it was assumed that they would not engage in mounting behavior with one another. Nevertheless, 12 percent of female pairs showed transfer of powder—but of course this was interpreted by researchers as evidence of nonsexual contact between such females (Ebensperger, L. A., and R. H. Tamarin [1997] “Use of Fluorescent Powder to Infer Mating Activity of Male Rodents,” Journal of Mammalogy 78:888- 93).

113

Rhesus Macaque (Erwin and Maple 1976); field report of penetration and ejaculation (Sade 1968:27); see also Kempf (1917:134) for an even earlier documentation of anal penetration between (captive) male Rhesus Macaques. Walther (1990:308) makes a parallel claim that mounting activity between male hoofed mammals does not constitute (homo)sexual behavior because erection and anal penetration are not always observed (Walther, “Bovids: Introduction”). On a related point, Tuttle (1986:289) takes great pains to point out that rump-rubbing and mounting between male Bonobos do not “qualify” as genital contact because, “pace certain sodomites, the anus is not a genital organ (International Anatomical Nomenclature Commitee, 1977, p. A49).” Tuttle does, however, accept that sexual activity between females—which he calls “bizarre homosexual hunching” (ibid., p. 282)—qualifies as genital contact (Tuttle, R. H. [1986] Apes of the World: Their Social Behavior, Communication, Mentality, and Ecology [Park Ridge, N.J.: Noyes Publications]). For a recent survey of homosexual behavior in primates that (wisely) drops the occurrence of penetration, arousal, and/or orgasm as a defining criterion of the behavior, see Vasey, “Homosexual Behavior in Primates,” p. 175.

114

On a similar gradation of mounting behavior in male birds, see Moynihan 1955:105 (Black-headed Gull).

115

For specific arguments against homosexual activity as a form of tension reduction in various species, see Yamagiwa 1987a:23, 1987b:37 (Gorilla); Edwards and Todd 1991:234-35 (White-handed Gibbon); Vasey 1996:549 -50 (Japanese Macaque); R. Wrangham, in Weinrich 1980:291 (Gelada Baboon). Against homosexuality as a form of play, see Talmage-Riggs and Anschel 1973:71 (Squirrel Monkey); Lombardo et al. 1994:556 (Tree Swallow). Against homosexuality as reconciliation or reassurance behavior, see Vasey 1996:550 (Japanese Macaque); Akers and Conaway 1979:78 (Rhesus Macaque); Lombardo et al. 1994:556 (Tree Swallow). Against homosexual activities as a means of forging coalitions or alliances, see Silk 1994:285—87 (Bonnet Macaque) (and also Silk 1993:187 for arguments that coalition-bonding between males in this species is not “functional” in terms of enhancing the males’ status, access to resources, or inclusive fitness). Against homosexuality as a gesture of appeasement or placation, see Manson et al. 1997:783 (White-faced Capuchin); Ferron 1980:136 (Red Squirrel); Lombardo et al. 1994:556 (Tree Swallow). Against homosexual relations as “kinship alliances” between individuals who associate with each other primarily because they are related (so-called kin selection), see Fernandez and Reboreda 1995:323 (Greater Rhea); Heg and van Treuren 1998:688-89, Ens 1998:635 (Oystercatcher); Afton 1993:232 (Lesser Scaup Duck); Rose 1992:104, 112 (Killer Whale); Hashimoto et al. 1996:316 (Bonobo). See also Vasey, “Homosexual Behavior in Primates,” for a summary and review of the evidence against many of these nonsexual “explanations.”

116

Japanese Macaque (Vasey 1996).

117

Bonobo (de Waal 1987, 1995 [among others]; Savage-Rumbaugh and Lewin 1994:110); Gorilla (Yamagiwa 1987a:23, 1987b:37).

118

See Silk 1994:285-87 (Bonnet Macaque) for more detailed discussion.

119

Signs of sexual arousal such as these have been documented for homosexual interactions in more than 90 species of mammals and birds. In addition, a number of scientists have themselves asserted the clearly sexual character of same-sex interactions (in addition to, or instead of, nonsexual aspects); see, for example, de Waal 1995:45—46 (Bonobo); Yamagiwa 1987a, Harcourt 1988:59, Porton and White 1996:724 (Gorilla); Edwards and Todd 1991 (White-handed Gibbon); Weber and Vogel 1970:76-77 (Hanuman Langur); Vasey 1996:550, Rendall and Taylor 1991:324, Wolfe 1984:147 (Japanese Macaque); Akers and Conaway 1979:78-79 (Rhesus Macaque); Chevalier-Skolnikoff 1976:525 (Stumptail Macaque); Srivastava et al. 1991 (Hanuman Langur); R. Wrangham, in Weinrich 1980:291 (Gelada Baboon); Manson et al. 1997:775-76 (White-faced Capuchin); Herzing and Johnson 1997:85, 90 (Bottlenose/Atlantic Spotted Dolphins); Saulitis 1993:58 (Killer Whale); Darling 1978:60, 1977:10—11 (Gray Whale); Coe 1967:320 (Giraffe); Rue 1989:313 (White-tailed Deer); Buss 1990:20 (African Elephant); Heg and van Treuren 1998:688 (Oystercatcher); Davis et al. 1998 (Adelie Penguin); Stiles 1982:216 (Anna’s Hummingbird). For use of the word erotic to characterize same-sex interactions, see, for example, de Waal 1987:323, 1997:103-4, Kano 1992:192, 1990:66 (Bonobo); Darling 1977:10—11 (Gray Whale); Mathews 1983:72 (Walrus); Buss 1990:19 (African Elephant).

120

Occasionally, however, multiple “functions” are granted to heterosexual behavior; see, for example, Lindburg 1971 (Rhesus Macaque); de Waal 1987, 1995, 1997, Kano 1990:67 (Bonobo); Manson et al. 1997 (White-faced Capuchin); Hanby, J. (1976) “Sociosexual Development in Primates,” in P. P. G. Bateson and P. H. Klopfer, eds., Perspectives in Ethology, vol. 2, pp. 1-67 (New York: Plenum Press).

Chapter 4. Explaining (Away) Animal Homosexuality

1

M. Grober, opening remarks to the plenary session on Sexual Orientation, 24^th International Ethological Conference, Honolulu, Hawaii, August 12, 1995.

2

Among the attendees who had previously documented or written extensively on animal homosexual behavior, but who were not speaking on this topic, were B. Le Boeuf (Northern Elephant Seals), C. Clark (Right Whales), W. D. Koenig (Acorn Woodpeckers), M. Moynihan (Rufous-naped Tamarins, Pied Kingfishers, Blue-bellied Rollers), A. Srivastava (Hanuman Langurs), F. B. M. de Waal (Bonobos, other primates), and J. C. Wingfield (Gulls). A number of other disconcerting trends were also in evidence among the papers presented during this symposium: for example, many were based on studies of laboratory or captive animals to the exclusion of information on homosexuality/transgender in wild animals. One presenter (Ulibarri) actually went so far as to state that no information was available in English on any behavior of wild Mongolian gerbils, when in fact at least one such study had been published several years earlier in a prominent zoology journal (Ulibarri, C. [1995] “Gonadal Steroid Regulation of Differentiation of Neuroanatomical Structures Underlying Sexual Dimorphic Behavior in Gerbils,” paper presented at the 24^th International Ethological Conference, Honolulu, Hawaii; Agren, G., Q. Zhou,