Biological Exuberance: Animal Homosexuality and Natural Diversity

Polyandrous Spotted Sandpiper, Actitis macularia,” Animal Behavior 47:1065-72).

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Redshank (Nethersole-Thompson and Nethersole-Thompson 1986:228); mustached warbler (Fessl, B., S. Kleindorfer, and H. Hoi [1996] “Extra Male Parental Behavior: Evidence for an Alternative Mating Strategy in the Moustached Warbler Acrocephalus melanopogon,” Journal of Avian Biology 27:88—91); Ostrich (Bertram 1992:125-26, 178); Greater Rhea (Navarro et al. 1998:117-18); Tree Swallow (Leffelaar and Robertson 1985); tropical house wren (Freed, L. A. [1986] “Territory Takeover and Sexually Selected Infanticide in Tropical House Wrens,” Behavioral Ecology and Sociobiology 19:197-206); barn swallow (Crook, J. R., and W. M. Shields [1985] “Sexually Selected Infanticide by Adult Male Barn Swallows,” Animal Behavior 33:754-61); Black Stilt (Pierce 1996:85); Silver Gull (Mills 1989:388); Herring Gull (Burger and Gochfeld 1981:128); African Elephant (Buss and Smith 1966:385—86; Kuhme 1963:117).

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White-handed Gibbon (Edwards and Todd 1991:234; Reichard 1995 a,b; Mootnick and Baker 1994); Ostrich (Sauer 1972:737); Buff-breasted Sandpiper (Lanctot and Laredo 1994:8; Pruett-Jones 1988:1748).

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American Bison (Komers et al. 1994:324; D. F. Lott, personal communication); Bonobo (Hashimoto 1997:12— 13).

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Musk-ox (Smith 1976:37, 56, 75-77; Gray 1979; Reinhardt 1985); Asiatic Elephant (Poole et al. 1997:304, 306—7 [fig. 5]); New Zealand Sea Lion (Marlow 1975:186, 203); Wolf (Zimen 1981:140); Killer Whale (Rose 1992:73, 83—84, 112, 116).

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Ruff (Hogan-Warburg 1966:178—79, 199-200; van Rhijn 1991:69); Pukeko (Jamieson et al. 1994:271; Jamieson and Craig 1987a); Ocher-bellied Flycatcher (Westcott 1993:450); Ruffed Grouse (Gullion 1981:377, 379 —80); Oystercatcher (Heg and van Treueren 1998: 689—90); Brown-headed Cowbird (Rothstein et al. 1986:150, 154—55, 167; Darley 1978); Guianan Cock-of-the-Rock (Trail and Koutnik 1986:209).

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Giraffe (Dagg and Foster 1976:123; Innis 1958:258-60); Japanese Macaque (Vasey 1996 and personal communication; Corradino 1990:360; Wolfe 1984); Hanuman Langur (Srivastava et al. 1991); Gray Seal (Backhouse 1960:310); Killer Whale (Jacobsen 1990:75-78); Zebras (Rasa and Lloyd 1994:186); Great Cormorant (Kortlandt 1949); Orange-fronted Parakeet (Hardy 1965:152-53); Wapiti (Lieb 1973:61; Graf 1955:73; Harper et al. 1967:37); Ducks (McKinney et al. 1983). Most of these cases are also examples of a “preference” for homosexual activity in the participating individuals.

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White-fronted Amazon Parrot (Clarke 1982:71); Long-eared Hedgehog (Poduschka 1981:81); Steller’s Sea Eagle (Pringle 1987:104); Barn Owl (Jones 1981:54); Rhesus Macaque (Erwin and Maple 1976:12-13); Crab-eating Macaque (Hamilton 1914:307-8); Bottlenose Dolphin (McBride and Hebb 1948:121); Cheetah (Ruiz-Miranda et al. 1998:7, 12); Black-headed Gull (van Rhijn and Groothuis 1987:142-43; van Rhijn 1985:91-93); Mallard Duck (Schutz 1965:442, 449—50, 460).

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Ring-billed Gull (Conover and Hunt 1984a); Greylag Goose (Huber and Martys 1993:157[fig.1]).

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Willson, M. F., and E. R. Pianka (1963) “Sexual Selection, Sex Ratio, and Mating Systems,” American Naturalist 97:405-7; Verner, J. (1964) “Evolution of Polygamy in the Long-billed Marsh Wren,” Evolution 18:252— 61; Verner, J., and M. F. Willson (1966) “The Influence of Habitats on Mating Systems of North American Passerine Birds,” Ecology 47:143—47; Wittenberger, J. E (1976) “The Ecological Factors Selecting for Polygyny in Altricial Birds,” American Naturalist 109:779-99; Wittenberger, J. E (1979) “The Evolution of Vertebrate Mating Systems,” in P. Marler and J. Vandenbergh, eds., Handbook of Neurobiology: Social Behavior and Communication, pp. 271-349 (New York: Plenum Press); Goldizen et al 1998 (Tasmanian Native Hen). For examples of (heterosexual) mating systems actually determining the sex ratio rather than vice versa, see Hamilton, W. D. (1967) “Extraordinary Sex Ratios,” Science 156:477-88; Wilson, D. S., and R. K. Colwell (1981) “Evolution of Sex Ratio in Structured Demes,” Evolution 35:882 -97.

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In Roseate Terns, for example, homosexual pairs were initially taken as evidence of skewed sex ratios, even though the sex ratio in this species had not yet been reliably determined (owing to the difficulty, until recently, of accurately determining the sex of individuals) (Sabo et al. 1994:1023, 1026).

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Western Gull (Hunt and Hunt 1977; Hunt et al. 1980; Wingfield et al. 1980; Fry and Toone 1981; Fry et al. 1987; Hayward and Fry 1993); Herring Gull (Fitch 1979; Shugart et al. 1987, 1988; Pierotti and Good 1994).

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For explicit refutation of an association between female homosexual pairs and environmental toxins, see Hunt 1980 (Western Gull); Lagrenade and Mousseau 1983; and Conover 1984c (Ring-billed Gull).

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Fry et al. 1987; Fry, D. M., and C. K. Toone (1981) “DDT-induced Feminization of Gull Embryos,” Science 213:922-24.

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Fry et al. 1987:37, 39; Fry and Toone 1981:923. Behavioral changes that could potentially be relevant have only been observed in other bird species, and only as a result of direct injection with estrogen, a female hormone, and not as a result of exposure to toxins (which mimic some of the effects of estrogen).

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Indeed, if toxin-induced “feminization” resulted in behavioral changes, one might even expect this to be manifested directly as male homosexuality (especially under a “pseudoheterosexual” interpretation, or one in which homosexuality is equated with intersexuality), yet this has not been reported for these populations either. Even if such homosexuality were to occur, however, it would not necessarily argue for reduced numbers of breeding males: homosexually paired males in several bird species (including Black-headed and Laughing Gulls) sometimes continue to copulate with females (i.e., they are functionally bisexual and their same- sex pair bonds are nonmonogamous).

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Herring Gull and other species (Fitch and Shugart 1983:6).

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Western Gull (Fry et al. 1987); Herring Gull (Burger and Gochfeld 1981; Nisbet and Drury 1984:88). In these populations scientists have suggested that perhaps a cofactor is involved: availability of nest sites (Fry et al. 1987:40). The hypothesis is that homosexual pairs will only form in sex-skewed populations if there are vacant nest sites, since female pairs presumably are less able to compete for territories in dense colonies. However, Hand (1980:471) argues that homosexual pairs can effectively obtain (and defend) territories even in dense colonies. In addition, Fetterolf et al. (1984) show that female pairs of Ring-billed Gulls in crowded colonies are simply relegated to less optimal nest sites, rather than failing to form in the first place (or disbanding) because of competition or crowding. This “cofactor” is also of limited applicability to other bird species. In Orange-fronted Parakeets, for example, female pairs compete successfully against heterosexual pairs for possession of nest sites (Hardy 1963:187), while in many species female pairs form regardless of whether they acquire nesting sites (i.e., homosexual pair-formation is independent of nesting).

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Herring Gull (Shugart et al. 1987, 1988); Ring-billed Gull (Conover and Hunt 1984a,b).

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Watson, A., and D. Jenkins (1968) “Experiments on Population Control by Territorial Behavior in Red Grouse,” Journal of Animal Ecology 37:595–614; Weatherhead, P. J. (1979) “Ecological Correlates