Biological Exuberance: Animal Homosexuality and Natural Diversity

Orientation: Some female Sage Grouse that mate with females do not apparently engage in heterosexual copulation; others alternate between homosexual and heterosexual activity (sometimes within a few hours or minutes). As described above, bisexual “pile-ups” involving birds of the same and opposite sexes mounting each other simultaneously also occur. In Ruffed Grouse, little is known about homosexual activity in the wild, but it is likely that there is a similar combination of bisexuality with occasional exclusive homosexuality. Displaying males that mount other males probably also court and mate with females, while those males who approach displaying males are most likely nondrumming “alternate” males (see below) that do not mate heterosexually.

Nonreproductive and Alternative Heterosexualities

In both of these species, significant portions of the population are nonbreeding. As many as 30 percent of male Ruffed Grouse are nondrummers who do not mate heterosexually, and some birds never breed during their entire lives. In fact, one researcher found that nonbreeders live longer and have a better survival rate than breeders. Many nonbreeders are younger males who have yet to acquire a drumming log; others are ALTERNATE males that tend to associate with another male on his display site without themselves drumming. Still others give up or “abdicate” their display territories and become nonbreeders. Up to 25 percent of female Ruffed Grouse may not nest in any given year, as is true for 20-32 percent of female Sage Grouse in some populations. Moreover, 14-16 percent of female Sage Grouse abandon their nests (especially if they have been disturbed), which means that any eggs or chicks they have will not survive; this also occasionally occurs in Ruffed Grouse. The majority of Sage Grouse copulations are performed by only a small fraction of the male population, and one-half to two-thirds of males never mate at all; during each breeding season, 3-6 percent of females do not ovulate either.

Even among birds that do mate, heterosexual copulation is often complicated by a host of factors: female Sage Grouse may refuse to be mounted, males often ignore females’ solicitations to mate (especially later in the breeding season), and 10–18 percent of copulations are disrupted by neighboring males who attack mating birds. In addition, males and females are often physically separated from each other: in both species, typically the only contact the two sexes have with each other during the breeding season is mating. Since each female usually copulates only once, hers is a largely male-free existence. Even on the display grounds, Sage Grouse are typically sex-segregated when not actually mating. Several types of alternative sexual behavior also occur in these species. Male Sage Grouse often “masturbate” by mounting a pile of dirt or a dunghill and performing all the motions of a full copulation. Both male Ruffed and Sage Grouse occasionally court and mate with females of other grouse species. And male Sage Grouse sometimes mount females without attempting to inseminate them (no genital contact). Moreover, even though most females mate only once (that is, the minimum required to fertilize their eggs), multiple copulations also occasionally occur: one female, for example, was mounted more than 22 times in one hour. Female Sage Grouse sometimes combine their youngsters into what is known as a GANG BROOD, a communal “nursery flock” of sorts.

Other Species

Homosexual activity occurs in several species of pigeons. Feral Rock Doves (Columba livia), for example, form both male and female same-sex pairs that engage in a full suite of courtship, pair-bonding, sexual, and nesting activities. Homosexual pairs of female Ring Doves (Streptopelia risoria) in captivity are generally more devoted incubators than heterosexual pairs, being less likely to abandon their eggs.

Sources

*asterisked references discuss homosexuality/transgender

*Allen, A. A. (1934) “Sex Rhythm in the Ruffed Grouse (Bonasa umbellus Linn.) and Other Birds.” Auk 51:180-99.

*Allen, T. O., and C. J. Erickson (1982) “Social Aspects of the Termination of Incubation Behavior in the Ring Dove (Streptopelia risoria).” Animal Behavior 30:345-51.

Bergerud, A. T., and M. W. Gratson (1988) “Survival and Breeding Strategies of Grouse.” In A. T. Bergerud and M. W. Gratson, eds., Adaptive Strategies and Population Ecology of Northern Grouse, pp. 473-577. Minneapolis: University of Minnesota Press.

*Brackbill, H. (1941) “Possible Homosexual Mating of the Rock Dove.” Auk 58:581.