37
Emu (Coddington and Cockburn 1995; Heinroth 1924); Black-rumped Flameback (Neelakantan 1962); Nilgiri Langur (Poirier 1970a,b); Harbor Seal (Johnson 1976:45); Northern Quoll (Dempster 1995); Gray-capped Social Weaver (Collias and Collias 1980); Walrus (Miller 1975; Fay et al. 1984); Acorn Woodpecker (Koenig and Stacey 1990:427); Australian Shelduck (Riggert 1977:20); Killer Whale (Jacobsen 1990:78; Rose 1992:1—2). See also Lutz and Voight 1994 for the first documentation of copulatory behavior—between two males—in two previously unknown species of deep-sea octopuses (a group in which heterosexual mating has yet to be observed in any species). Other animals in which same-sex activity has been documented and in which heterosexual activity has rarely been observed include Musk-oxen (Smith 1976:62), Red-necked Wallabies (Johnson 1989a:275), Vicunas (Koford 1957:182-84), Musk Ducks (Lowe 1966:285), and Ruffed Grouse (Johnsgard 1983:295). See chapter 4 for further discussion of the often insurmountable difficulties in attempting to observe and study sexual activity under field conditions.
38
Ring-billed Gull (Conover and Aylor 1985). See chapter 4 for discussion of some of the pitfalls of equating homosexual pairings with supernormal clutches.
39
Dragonflies (Dunkle 1991).
40
Pukeko (Craig 1980); Pronghorn (Kitchen 1974). The behavior was probably classified as rare in Pronghorn because the amount of same-sex activity was not being compared to the amount of opposite-sex activity, but rather to the total amount of “dominance” behavior (which it was classified as), consisting primarily of nonsexual activities. For further discussion and critique of homosexuality interpreted as a “dominance” activity, see chapter 3.
41
Killer Whale (Rose 1992:116); Regent Bowerbird (Lenz 1994:266 [table 2]); White-handed Gibbon (Edwards and Todd 1991:233 [table 1]); Crab-eating Macaque (Thompson 1969:465).
42
Giraffe (Pratt and Anderson 1985, 1982, 1979). In a study of another population of Giraffes, only three mounts between males were recorded, but only 400 hours of observation were involved (Dagg and Foster 1976:124).
43
Mountain Sheep (Geist 1968:210-11 [tables 4, 6]); 1971:152 [table 30]).
44
Gray Heron (Ramo 1993:116-17). In some species (e.g., Little Egrets, Little Blue Herons) quantitative information is only available for the proportion of promiscuous copulations that are homosexual (the higher figure). Where both proportions are available (e.g., Cattle Egrets, Gray Herons), an average of the two is taken when calculating cross-species comparisons of frequency (see below). Different frequencies can also be obtained depending on whether a distinction between copulatory and noncopulatory (or “ritualized”) mounting is taken into account. (See chapter 3 for discussion of the—sometimes arbitrary—distinction between these two types of mounting.) In some cases, such as Pig-tailed and Crested Black Macaques, a sizable difference obtains. In Pigtails, 82 percent of mounting is same-sex if only noncopulatory mounts are considered (Oi 1990a:350-51 [table 4]), whereas 7-23 percent of all mounts are same-sex if “full” heterosexual copulations are included in the calculation (Bernstein 1967:226-7; Oi 1996:345). In Crested Blacks, roughly a third of noncopulatory mounts are between males, but overall this constitutes only about 8 percent of mounting activity when combined with copulatory (heterosexual) mounts (C. Reed, personal communication). In cases such as these, the latter (smaller) percentage is taken to be the overall rate of same-sex activity. For other species, however, the two rates are comparable. In Common Chimpanzees, for example, Nishida and Hosaka (1996:122, 129 [tables 9.7, 9.17a]) recorded 61 ritualized mounts between males compared to 123 male-female copulations (nonritualized), yielding a rate of 33 percent same-sex mountings. This is comparable to the exclusively noncopulatory figures of Bygott (1974; cited in Hanby 1974:845 [Japanese Macaque]), who found that 4 of 14 ritualized mounts (29 percent) occurred between males.
45
Of course, these cross-species comparisons refer only to those animals in which homosexual behavior has been observed and in which the appropriate quantitative information is available. In many species same-sex behavior is more or less common than the maximum and minimum figures obtained from these measures, but it has not been quantified and therefore cannot be compared to these examples. For these calculations, if multiple frequency proportions were available for the same species—either because of population, seasonal, or behavioral differences (as discussed above)—these were averaged prior to being combined with the figures for other species. Proportions for courtship behavior are based on quantitative information from 21 species (avg = 23 percent same- sex activity), for sexual behavior from 77 species (avg = 26 percent), for pairing behavior from 45 species (avg = 14 percent), and for population percentages from 56 species (avg = 27 percent). For the purposes of comparison, tallies of observed homosexual and heterosexual behaviors in each species are assumed to be representative of actually occurring frequencies. The statistics for pairing and sexual behavior do not include the many species in which the
46
The term
