relations with several different “favorite” partners or consorts (of both sexes). Males in homosexual pairs of Greylag Geese, Laughing Gulls, Humboldt Penguins, and Flamingos sometimes engage in “promiscuous” copulations with birds (male or female) other than their mate (heterosexual pairs in these species are also sometimes nonmonogamous). Another form of nonmonogamy occurs among lesbian pairs in a number of Gulls and other birds: one or both females sometimes mate with a male (while still maintaining their same-sex bond) and are thereby able to fertilize their eggs and become parents.
The second main type of homosexual pairing is the “companionship.” Two animals of the same sex may bond with each other, often spending most of their time together exclusive of the opposite sex, but they do not necessarily engage in recognizable courtship or sexual activities with each other. For example, older African Elephant bulls sometimes form long-lasting associations with a younger “attendant” male: these animals are loners, spending all their time with each other rather than with other Elephants, helping each other, and never engaging in heterosexual activity. Male Calfbird companions display and travel together and also sometimes share a “home” with one another (a special perch known as a retreat where they spend time away from the display court). Similar same-sex associations are found in many other species, including Orang-utans, Gray Whales, Grizzly Bears, Vampire Bats, and Superb Lyrebirds. Younger same-sex attendants are known as satellites in male Moose and shadows in male Walruses, while companions are called duos in male Hanuman Langurs and spinsters in female Warthogs—the latter is something of a misnomer, though, since Warthog companions do occasionally participate in sexual activity with males or females, but not necessarily with their companions.
Sometimes more than two animals bond together, forming a “trio” (in either partnership or companionship form). This arrangement can consist of three animals all of the same sex who are bonded with each other, as occasionally happens among female Ring-billed Gulls and male African Elephants, White-tailed Deer, and Black- headed Gulls. Trios can also be bisexual, consisting of two females and one male (e.g., Canada Geese, Common Gulls, and Jackdaws) or two males and one female (Greylag Geese, Black Swans, Sociable Weavers); in Oystercatchers, both types occur. In either form of a bisexual trio, there is significant bonding, courtship, and/or sexual behavior between the two animals of the same sex. This distinguishes such associations from heterosexual trios, in which two animals of the same sex are bonded with an opposite-sexed individual but not to each other. Same-sex trios of closely bonded male Greylag Geese or female Grizzly Bears are also sometimes known as triumvirates, while bisexual (and heterosexual) trios in Flamingos are called triads. In a few species, “quartets” involving simultaneous homosexual and heterosexual bonds between four individuals sometimes occur: in Greylag Geese and Black-headed Gulls, for instance, three males and a female sometimes bond with each other, while in Galahs, two males and two females may associate in a quartet with various bonding arrangements between them.
Homosexual pair-bonds vary not only in their type, but also in their duration. Same-sex bonding often follows the species-typical pattern for heterosexual pairing in terms of how long it lasts. In species such as the Greylag Goose, for example, which remain mated for life (or else for many consecutive years), male pairs are also generally long-lasting or lifelong, while in Bison, tending bonds usually last only a few days or hours in both heterosexual and homosexual situations. In some cases, long-term pair bonding involves continuous association throughout the year, as among male Ocellated Antbirds. This contrasts with seasonal association, for example among several species of Gulls, in which females re-pair with the same female only during the mating season. Homosexual pairs may also be of shorter duration than heterosexual ones in some species: Black-headed Gull male couples, for example, appear to be more prone to divorce than heterosexual ones. However, in many cases homosexual pairings, particularly companionships, actually exceed heterosexual ones in their stability and duration. Among Lions and Elephants, for example, the bond between male companions is closer and longer-lasting than any heterosexual bonds (which, in these and many other species, are virtually nonexistent beyond mating), while mated gander pairs in Greylag Geese are often more strongly bonded than heterosexual pairs. Consortships between Japanese Macaque females sometimes develop into yearlong friendships, unlike the majority of heterosexual associations in this species. In fact, in a number of animals the only pair-bonds that occur are homosexual, not heterosexual. Male Bottlenose Dolphins, for example, form lifelong partnerships with each other, while males and females in this species do not generally pair-bond with one another at all. Other animals with same-sex but not opposite-sex pairings (often in the form of companionships) include Musk-oxen, Wapiti, White-tailed Deer, Warthogs, Cheetahs, Eastern Gray Kangaroos, Red Squirrels, and Calfbirds.
Formidable Fathers and Supernormal Mothers: Homosexual Parenting
Same-sex pairs in many species (especially birds) raise young together. Not only are they competent parents, homosexual pairs sometimes actually exceed heterosexual ones in the number of eggs they lay, the size of their nests, or the skill and extent of their parenting. How are such animals able to have offspring in the first place if they are in homosexual associations? Many different strategies are used, including several in which one or both partners are the biological parent(s) of the young they raise together. The most common parenting arrangement of this type is found in lesbian pairs of several Gull, Tern, and Goose species: one or both female partners copulate with a male to fertilize her eggs. No bonding or long-term association develops between the female and the male (who is essentially a “sperm donor” to the homosexual pair), and the youngsters are then jointly raised by both females without any assistance from a male parent. Because female birds can lay eggs regardless of whether they are fertilized, however, each partner in a lesbian pair usually contributes a full clutch of eggs to their nest even if she hasn’t mated with a male. As a result, female homosexual pairs often lay what are called supernormal clutches, that is, double the number of eggs usually found in nests of heterosexual pairs.10
Sometimes two female animals who already have offspring join forces, bonding together and raising their young as a same-sex family unit (among mammals, female coparents may even suckle each other’s young): this occurs in Grizzly Bears, Red Foxes, Warthogs, Dwarf Cavies, Lesser Scaup Ducks, and Sage Grouse. Notably, heterosexual pairs do not occur in these species, and most offspring are otherwise raised by single females.11 In some species, a nonbreeding animal bonds with a (single) breeding animal and helps parent its young: this occurs in Squirrel Monkeys, Northern Elephant Seals, Jackdaws (where a widowed female with young may pair with a single female), and Greater Rheas (where one male may help another incubate his eggs and then raise the young together). In most such joint parenting arrangements (as opposed to homosexual mated pairs), there is not necessarily any overt courtship or sexual activity between the bonded coparents, although in some species (e.g., Squirrel Monkeys, Northern Elephant Seals, Emus, Sage Grouse), homosexual activity does occur in contexts
In a number of cases, homosexual pairs raise young without being the biological parents of the offspring they care for. Some same-sex pairs adopt young: two female Northern Elephant Seals occasionally adopt and coparent an orphaned pup, while male Hooded Warblers and Black-headed Gulls may adopt eggs or entire nests that have been abandoned by females, and pairs of male Cheetahs occasionally look after lost cubs. Sometimes female birds “donate” eggs to homosexual couples through a process known as parasitism: in many birds, females lay eggs in nests other than their own, leaving the parenting duties to the “host” couple. This occurs both within the same species, and (more commonly) across species, and usually involves heterosexual hosts. Male pairs of Hooded Warblers, however, sometimes receive eggs from Brown-headed Cowbirds (and possibly also from females of their own species) in this way; within-species parasitism may also provide eggs for male pairs of Black-headed Gulls and female pairs in Roseate and Caspian Terns. The opposite situation is thought to occur in Ring-billed Gulls: researchers believe that some homosexually paired females actually lay eggs in nests belonging to heterosexual pairs. Finally, some birds in same-sex pairs take over or “kidnap” nests from heterosexual pairs (e.g., in Black Swans, Flamingos) or occasionally “steal” individual eggs (e.g., in Caspian and Roseate Terns, Black-headed Gulls); homosexual pairs in captivity also raise foster young provided to them.
