33
For example, an animal could participate in a large number of heterosexual copulations, only a few of which would actually lead to fertilization (not to mention successful birth or rearing of offspring), while an animal with fewer heterosexual encounters could have a higher proportion of fertilizations or successful pregnancies or could be a better parent. Moreover, females who mate repeatedly during one breeding season can only get pregnant or be fertilized once, effectively equalizing the difference between greater and lesser participation in heterosexual mating (unless promiscuity is positively correlated with parenting success). For further discussion of how copulation frequency does not necessarily reflect reproductive output, see Eberhard, W. G. (1996)
34
It should also be reiterated that detailed longitudinal studies of breeding success and sexual orientation (comparble to that done on Silver Gulls) have not been conducted on any of these species to verify possible connections between bisexuality and reproduction. Moreover, all of these cases involve homosexuality among members of only one gender, which again is inconsistent with a “bisexual superiority” hypothesis.
35
Bonobo (Hashimoto 1997:12-13); Gorilla (Fossey 1990:460, 1983:74, 188-89); Squirrel Monkey (Mendoza and Mason 1991:476-77); Wolf (Zimen 1976:311, 1981:140); Common Tree Shrew (Kaufmann 1965:72); Bottlenose Dolphin (Ostman 1991:310). For arguments that this is not merely “displaced,” “redirected,” or “vicarious” heterosexuality (as Fossey [1990:460] and others have labeled it), see the discussion of the “shortage” hypothesis in chapter 4.
36
Guianan Cock-of-the-Rock (Trail and Koutnik 1986:215); Oystercatcher (Heg and van Treuren 1998:690; D. Heg, personal communication).
37
Kob (Buechner and Schloeth 1965:219 [table 2]).
38
Cattle Egret (Fujioka and Yamagishi 1981:136, 139 [including tables 1, 3, 4]).
39
See the profile of the Ruff for further details and illustrations.
40
Ruff (Van Rhijn 1991:87; Hogan-Warburg 1966:176).
41
Ruff (Lank et al. 1995). Nearly 30 years previously, Hogan-Warburg (1966) and van Rhijn (1973) had suggested that there might be genetic differences between various categories of males, based on the indirect evidence of their plumage and behavioral distinctions as well as the constancy of their category status. This hypothesis was subsequently confirmed by DNA and heredity studies.
42
Red Flour Beetle (Castro et al. 1994; Serrano et al. 1991); Fruit Flies (numerous references, summarized in Finley et al. 1997). See also Hamer and Copeland (1994) on the role of genetics in human homosexuality.
43
This has been suggested for species such as Stumptail Macaques, White-faced Capuchins, Killer Whales, Northern Elephant Seals, West Indian Manatees, Giraffes, Gray-headed Flying Foxes, Ring-billed Gulls, Black-headed Gulls, Ocher-bellied Flycatchers, Guianan Cock-of-the-Rock, Calfbirds, Superb Lyrebirds, and Adelie Penguins. In addition, in some species where homosexual behavior is classified as “play,” the implication is also that it functions as practice for “real” (i.e., heterosexual) activity.
44
Rhesus Macaque (Akers and Conaway 1979:76-77); Tree Swallow (Lombardo et al. 1994:556).
45
In a number of species, though, homosexual activity is restricted to juvenile or younger animals (see Dagg, “Homosexual Behavior and Female-Male Mounting in Mammals,” for a survey of such cases).
46
See Baker and Bellis,
47
Guianan Cock-of-the-Rock (Trail and Koutnik 1986:209, 215). These scientists admit that they have no specific data to support the conjecture that courtship interactions between males actually improve the subsequent heterosexual performance of younger males.
48
See below for discussion and refutation of the (related) idea that homosexuality is a form of courtship “disruption” in this species.
49
See Rose et al. (1991:188) for a statement to this effect concerning Northern Elephant Seals. The Ocher- bellied Flycatcher is another species where the relative infrequency of this behavior is curiously at odds with its putative “practice” function (see Westcott and Smith [1994:681] for the suggestion that courtship interactions between males in this species may allow younger birds to gain courtship experience).
50
Sage Grouse (Patterson 1952:153-54); Pandolfi, M. (1996) “Play Activity in Young Montagu’s Harriers (
51
For a similar conclusion regarding this “explanation” for primates, see Vasey, “Homosexual Behavior in Primates,” p. 192. See also Wagner (1996:212) on Razorbills.
52
The only example specifically involving females is the Ring-billed Gull, and notably in this case it is experience with parenting or pair-bonding, not sexual behavior, that females are claimed to acquire through homosexual partnerships (Fox and Boersma 1983:555).
53
On the myth of female passivity in sexual interactions, as well as the generally sexist interpretations of female behavior and physiology in this regard, see Eberhard,
54
For examples of scientists who have argued (or suggested) that homosexuality promotes or strengthens social bonds or general social cohesion and stability, see Kano 1992:192 (Bonobo); Yamagiwa 1987a:1, 23, 1987b:37, Robbins 1996:944 (Gorilla); Weber and Vogel 1970:79 (Hanuman Langur); Reinhardt et al. 1986:55 (Rhesus Macaque); Rose 1992:97—98, 116—17 (Killer Whale); Coe 1967:319 (Giraffe); Nelson 1965:552 (Gray- headed Flying Fox); Heg and van Treuren 1998:688, Ens 1998:635 (Oystercatcher); Sauer 1972:735 (Ostrich); Rogers and McCulloch 1981:90 (Galah). One scientist suggests that homosexual activity in Bonobos, although promoting bonding between same-sex individuals, actually serves a more important role in
55
See chapter 4 for further discussion and refutation of the idea that this is the motivation (or adaptive
