Biological Exuberance: Animal Homosexuality and Natural Diversity

Thompson 1975 (Scottish Crossbill), Wingfield et al. 1980 (Western Gull), Braithwaite 1981 (Black Swan), Smith 1988 (Lyrebird), Diamond 1989 (Snow Goose), Reed 1993 (Black Stilt).

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And in fact just such a “broad” definition of heterosexuality is required in many cases. “Heterosexual pairs” in which little or no sexual activity occurs between partners have been reported for Greylag Geese (as mentioned above) and Lesser Scaup Ducks (Afton 1985:150), among others; see also Loy (1971:26) for “sexual” bonds between male and female Rhesus Macaques that do not involve mounting or copulation, and Smuts (1985:18, 163—66, 199, 213) on the platonic “pair-bonds” or “friendships” between male and female Savanna Baboons. In addition, in some “heterosexual pairs” of splendid fairy-wrens all offspring are fathered by males other than the female’s pair-bonded mate (i.e., she does not copulate—or at least is not fertilized by—her partner); see Russell, E., and L Rowley (1996) “Partnerships in Promiscuous Splendid Fairy-wrens,” in J. M. Black, ed., Partnerships in Birds: The Study of Monogamy, pp. 162-73 (Oxford: Oxford University Press). For an example of a “broad” definition of (hetero)sexuality that encompasses courtship activities in addition to overt copulatory behavior, see Tinbergen, N. (1965) “Some Recent Studies of the Evolution of Sexual Behavior,” in F. A. Beach, ed., Sex and Behavior, pp. 1—33 (New York: John Wiley and Sons).

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In discussing the possible dangers of anthropomorphism in terminology, the comments of biologist John Bonner are instructive: “An anthropologist might find the use of words such as slaves or castes for ant colonies most undesirable … . For instance, it implies that the most repugnant human morals are ascribed to the members of some species of ant … . Much worse, it could imply that if ants have slavery, it is a natural thing to do and therefore quite justified in a human society. These arguments are not quite rational and can only be advanced under extreme fervor of one sort or another. A more reasoned objection would be that the motivations of ants and men might differ radically, but by using the same words this distinction is lost. A biologist, on the other hand, feels that the points made above are too obvious to interfere with the dual use of the words. He does not see any problem: in both ant and human slavery individuals forcibly capture members of their own species or related species and cause their captives to do work for the benefit of the captors. It is unnecessary to drag in all the possible political, psychological, or strictly human nuances; a very simple definition of the word is sufficient. There is no need to be tyrannized by words. If a biologist may not use the common words, he will be forced to invent a whole new set of jargon terms for nonhuman societies, an unfortunate direction since there are too many jargon words in any science as it is. I hope it will be sufficient if I make it clear in the beginning that words either invented or frequently used for human societies will also be used for animal societies with the understanding that I am not implying anything human in their meaning; they are to be considered simple descriptions of conditions.” (Bonner, J. T. [1980] The Evolution of Culture in Animals, pp. 9—10. [Princeton, N.J.: Princeton University Press].) Unfortunately, this eminently reasonable position has not been adopted by most biologists where homosexuality is concerned; for a counterview, sec Gowaty, “Sexual Terms in Sociobiology.”

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Examples of species in which homosexual activity is given only cursory treatment compared to heterosexual activity are too numerous to list, but include White-tailed Deer (Hirth 1977), Wapiti (Harper et al. 1967), Fat-tailed Dunnart (Ewer 1968), Matschie’s Tree Kangaroo (Hutchins et al. 1991), Wattled Starling (Sontag 1991), Sage Grouse (Wiley 1973, Gibson and Bradbury 1986), and Canary-winged Parakeet (Arrowood 1988). In a few studies, however, detailed quantitative and descriptive information is provided on homosexual behavior; see, for example, Kitamura 1989, Kano 1992, de Waal 1987, 1995, 1997 (Bonobo); Edwards and Todd 1991 (White-handed Gibbon); Hanby 1974, Eaton 1978, Chapais and Mignault 1991, Vasey 1996 (Japanese Macaque); Pratt and Anderson 1985 (Giraffe); Jamieson and Craig 1987a (Pukeko); van Rhijn and Groothuis 1985, 1987 (Black-headed Gull); Rogers and McCulloch 1981 (Galah). For further discussion of how same-sex activity has frequently not been considered “genuine” sexual behavior, see the next section.

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Spinner Dolphin (Wells 1984:468; Bateson 1974); Kob (Buechner and Schloeth 1965:219 [table 21]); Crested Black Macaque (Dixson 1977); Brown Capuchin (Linn et al. 1995); Giraffe (Dagg and Foster 1976:75—77).

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Western Gull (Hunt et al. 1984:160) (see Hayward and Fry [1993:16, 18] for a recent reiteration of the findings of this study, in which sexual activity is once again downplayed); Black-crowned Night Heron (Noble et al. 1938:28-29); on comparable levels of crowding in wild colonies, see Gross 1923:13—15; Davis 1993:6; Kazantzidis et al. 1997:512); Laughing Gull (Hand 1985:128); Canary-winged Parakeet (Arrowood 1988. 1991); Greater Rhea (Fernandez and Reboreda 1998:341); Zebra Finch (Burley 1981:722).

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Gorilla (Harcourt 1979a:255). Harcourt et al. (1981:266) also characterize heterosexual copulation as “rare.” In addition, they report directly observing only 69 episodes of heterosexual mating (other copulations were heard but not seen) compared to 10 episodes between females, which yields an even higher proportion of nearly 13 percent homosexual activity.

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Western Gull (Hunt et al 1980:474); Spotted Hyena (Glickman 1993; Burr 1996:118-19); for further discussion of comparisons between wild and captive animals, see the next chapter

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Tree Swallow (M. P. Lombardo, personal communication: Venier et al. 1993:413; Lombardo 1986; Leffelaar and Robertson 1984:78). Similarly, homosexual mounting is claimed to be very rare in Northern Fur Seals, yet most heterosexual matings in this species are missed by observers because they occur at night (Gentry 1998:75—77, 107, 145).

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For specific examples, see Nilgiri Langur (Poirier 1970; Hohmann 1989). White tailed Deer (Hirth 1977: Rue 1989), Mule Deer (Geist 1981; Halford et al. 1987; Wong and Parker 1988), Red Deer (Lincoln et al. 1970; Guiness et al. 1971; Hall 1983), American Bison (McHugh 1958: Lott 1983 and personal communication), Red Squirrel (Layne 1954; Smith 1968; Ferron 1980), Mallard Duck Ramsey 1956; Lebret 1961; Schutz 1965; Bossema and Roemers 1985; Geh 1987), Ruff (Selous 1906—7; Bogan-Warburg 1966; Scheufler and Stiefel 1985; van Rhijn 1991), Oystercatcher (Makkink 1942; Heg and van Treuren 1998), Hooded Warbler (Niven 1994 and personal communication), Cliff Swallow (Emlen 1954, Barlow et al. 1963; Brown and Brown 1996), Red-backed Shrike (Owen 1946; Ashby 1958; Pounds 1972), Victoria’s Riflebird (Bourke and Austin 1947; Frith and Cooper 1996; C. B. Frith, personal communication), Sage Grouse (Scott 1942; Patterson 1952; Wiley 1973; Gibson and Bradbury 1986), Acorn Woodpecker (MacRoberts and MacRoberts 1976; Troetschler 1976; W. D. Koenig, personal communication), Gentoo Penguin (Robert 1934; Wheater 1976; Stevenson 1983), and the examples of wild versus captive observations in notes 99-100, chapter 4.

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Pukeko (Craig 1980:594; Jamieson and Craig 1987a;1252); Blak-headed Gull (van Rhijn and Groothuis 1985:161, 165).

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For example, Vasey (“Homosexual Behavior in Primates,” p. 181) sets up a general frequency scale in which homosexual behavior is classified as “rare” if it occurs “5 percent or less frequently as heterosexual behavior” and “occasional” if it occurs “6—24 percent as frequently as heterosexual behavior”; it is regarded as “frequent” only if it occurs “25 percent or more frequently.”Certainly this scale is to be commended for its standardization and multipoint assessment criteria (which also include nonquantitative measures); yet (like most scales) it is not without arbitrarines, and it is at odds with the heterosexual “5 percent” criterion. The “Polygyny threshold” model, which recognizes a frequency of ?5 percent as significant for “minority” heterosexual mating systems (i.e., polygamy in otherweise monogamous species) was originally proposed by Verner, J., and M. P. Willson (1966) “The Influence of Habitats on Mating Systems of North American Passerine Birds,” Ecology 47:143-47. The 5 percent threshold continues to be widely used as a criterion for “regular” polygyny—for more recent examples, see Quinney 1983 (Tree Swallow); Moller, A. P. (1986) “Mating Systems Among European Passerines. A Review,” Ibis 128:234—50; Petit, L. J. (1991) “Experimentally Induced Polygyny in a Monogamous Bird Species: Prothonotary Warblers and the Polygyny Threshold,”