[1993] “A Male Trait Expressed in Female Pied Flycatchers
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Tree Swallow (Lombardo et al. 1994:555–56; Venier et al. 1993; Venier and Robertson 1991); Black-crowned Night Heron (Noble et al. 1938:29); Regent Bowcrbird (Marshall 1954:114-16); Greenshank (Nethersole-Thompson and Nethersole-Thompson 1979:114; Nethersole-Thompson 1951:104). In Tree Swallows, it is also unlikely that males cooperate during homosexual copulations in order to “appease” the birds mounting them and thereby avoid attack or injury (as suggested by Lonrbsrdo et al. 1994:556). Aggressive attacks in this species are characterized by a number of distinctive behavioral elements on the part of both the attacker (e.g., threat displays, grappling, pecking) and the bird being attacked (e.g., appeasement displays, submissive and distress calling) (cf. Robertson et al. 1992:6, 8)—and homosexual mountings exhibit none of these hallmarks.
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Such cases contrast markedly with ones in which the pursued animal is clearly not a willing participant, such as Mountain Goats, Common Murres, or Anna’s Hummingbirds. In these instances, however, there are other arguments against a sex misrecognition analysis (as mentioned previously).
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Swans (Kear 1972:85-86).
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Wattled Starling (Sontag 1991:6); Common Chimpanzee (Kollar et al. 1968:444, 458); Gorilla (Coffin 1978:67); Stumptail Macaque (Bernstein 1980:32); Musk-ox (Reinhardt 1985:298-99); Koala (Smith 1980:186); Long-eared Hedgehog (Poduschka 1981:81; Reeve 1994:189); Vampire Bat (Greenhall 1965:442); Black-crowned Night Heron (Noble et al. 1938:14, 28-29). Factors such as stress or crowding have also been invoked for wild animals, such as Blue-bellied Rollers (Moynihan 1990).
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Dolphins (Pilleri, G. [1983] “Cetaceans in Captivity,”
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Cheetah (Eaton 1974a:116); Zebra Finch (Immelmann et al. 1982:422). The assessment for Cheetahs is particularly inappropriate in light of the fact that heterosexual activity is extremely difficult to observe in this species in the wild. As mentioned in chapter 1, during one ten-year study of Cheetahs, no heterosexual matings were seen over 5,000 hours of observation, and copulation has only been observed a total of five times in the wild during the entire scientific study of this species (Caro 1994:42). It is hardly surprising, therefore, that homosexual courtship and mating activity has so far only been seen in captivity. It should also be pointed out that male “coalitions” (bonded pairs or trios)
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Fedigan 1982:143 (Japanese Macaque). See also Crews et al. (1983:228-30) and Crews and Young (1991:514) for similar statements challenging the supposed “abnormalcy” of same-sex copulation among Whiptail Lizards in captivity versus the wild.
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In a few cases, specific homosexual activities, rather than the occurrence of homosexuality itself, have been observed in only wild or captive conditions. In Bonobos, for example, penis-fencing (a form of genital rubbing) has only been seen in the wild, while fellatio has only been observed in captivity (de Waal 1997:103–4). In addition, the duration of sexual acts can vary contextually: for example, de Waal (1987:326) found that episodes of genital rubbing between female Bonobos were considerably shorter in captivity (averaging around 9 seconds) than in the wild (averaging around 15 seconds).
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Orang-utan (Nadler 1988: 107); Hamadryas Baboon (Kummer and Kurt 1965:74); Mule Deer (Halford et al. 1987:107); Musk-ox (Reinhardt 1985:298).
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Bonobo, wild (Kano 1992:187 [table 24], 140; Kitamura 1989:53, 55-57, 61); Bonobo, captive (de Waal 1995:41 [table 3.1]); Black Swan (Braithwaite 1981:141-42). Five other species for which the relevant quantitative information is available are Pig-tailed, Crested Black, and Stumptail Macaques, Common Chimpanzees, and Vervets. Although the wild (or semi-wild) and captive figures in these cases are more difficult to compare (due to differences in group size and composition, observed behaviors, length of study periods, etc.), they also generally show fairly comparable rates. For Pig-tailed Macaques in the wild, 7-23 percent of mounting is same-sex, compared to about 25 percent in captivity (rates in the wild based on information in Oi 1990a:350—1 [including table [V], Oi 1996:345, and Bernstein 1967:226-27; captivity—Tokuda et al. 1968:287, 291 [table 7]). Among captive Crested Black Macaques, about 5 percent of mounting is between males (Dixson 1977:74, 77), compared to an estimated 8 percent in the wild (C. Reed, personal communication; figures for both of these species combine “copulatory” with “noncopulatory” mounts). However, another study (Bernstein 1970:94 [table IV]) yielded a much higher rate of same-sex mountings in captivity for these species—49 percent for Pigtails, 22 percent for Crested Blacks— demonstrating that there can be considerable differences between individual studies and/or populations (see also Bernstein [1967:228] for more on wild/captive comparisons in Pigtails). In Stumptail Macaques, 25 percent of sexual interactions (of all types) in captivity are homosexual (Chevalier-Skolnikoff 1974:100-101, 110), compared to 30-40 percent for mounting in a semi-wild troop (formerly captive animals that were transplanted and released) (Estrada et al. 1977:667 [fig.14]; Estrada and Estrada 1978:672 [table 4]). In Common Chimpanzees, same-sex mounting actually occurs more frequently in the wild: de Waal and van Hooff (1981:182 [table 2]) found that mounting between males in captivity constitutes only 1-2 percent of the behaviors involved in reassurance, enlistment of support, and other activities during conflicts, while Nishida and Hosaka (1996:120-21 [tables 9.5-9.6]) found that mounting accounts for one-third to one-half of such behaviors in wild Chimps. Likewise, Bernstein (1970:94 [table IV]) found that 9 percent of mounting activity in captive Vervets is same-sex, while Gartlan (1969:144, 146) and Struhsaker (1957:21, 27 [tables 8, 10]) both recorded 11 percent same-sex mounting in the wild. Rowell (1967b) also conducted a detailed quantitative comparison of behavioral frequency rates in the wild
