Biological Exuberance: Animal Homosexuality and Natural Diversity

Other patterns of exclusivity occur as well. In Nilgiri Langurs and Hamadryas Baboons, for instance, generally only the highest-ranking male in a group mates with females; remaining males, if they engage in sexual activity at all, are sometimes involved only in homosexual pursuits. In Nilgiri Langurs, cases of nonbreeding males having only same-sex interactions for at least four years have been documented. In Ruffs, there are several different categories of males, many of whom rarely, if ever, mate heterosexually; some of these individuals participate in homosexual activities and may do so over an extended period, perhaps even for life. Finally, in some species same-sex activity may be exclusive because it is incestuous, involving a parent and its nonbreeding offspring. In male White-handed Gibbons, for instance, father-son sexual relations may continue for several years; the son is not involved in concurrent heterosexual activity, and sometimes even his father may have little or no opposite-sex mating during this time. Red Fox daughters can remain with their family group for many years—sometimes they never leave—during which time they may be involved in occasional same-sex mounting with their mothers (or each other) but no heterosexual activity.¹⁸

Thus, while in many species documentation of exclusive long-term homosexuality (or heterosexuality, for that matter) is not directly available, exclusivity can be inferred from the general patterns of social organization in the species. For example, a system that involves large numbers of nonbreeders (including individuals who never mate heterosexually during their entire lives), combined with homosexual activities among at least a portion of these nonbreeding animals (sometimes in sex-segregated groups), will invariably entail some individuals whose only sexual contacts are with animals of the same sex. For some animals this period of exclusive homosexuality lasts no more than a few years; for others, it may extend considerably longer, even for the duration of their lives.

Shorter periods of exclusive or “preferential” homosexuality also occur. Sexual “friendships” in Stumptail Macaques and Rhesus Macaques, for example, and homosexual consortships in Japanese Macaques, last anywhere from a few days to several months, during which time there are no heterosexual involvements. During the seasonal aggregations of male Walruses and Gray Seals, same-sex activity usually occurs to the exclusion of opposite-sex behavior. Female Marmots forgo breeding for a couple of years but may still have sexual contact with other females. Same-sex pair bonds in King Penguins and homosexual associations in female Orang-utans are also exclusive for their duration. Of course, many of these animals are actually bisexual because they also engage in heterosexual pursuits at other times during their lives, but while they are involved in same-sex activity, they do not simultaneously engage in opposite-sex behavior. Thus, when considering various forms of exclusive homosexuality it is also necessary to understand the different types of nonexclusive homosexuality—that is, bisexuality.