Among animals in a domesticated or confined state it is easy to find evidence of homosexual attraction, due merely to the absence of the other sex.[2] This was known to the ancients; the Egyptians regarded two male partridges as the symbol of homosexuality, and Aristotle noted that two female pigeons would cover each other if no male was at hand.  Buffon observed many examples, especially among birds.  He found that, if male or female birds of various species—­such as partridges, fowls, and doves—­were shut up together, they would soon begin to have sexual relations among themselves, the males sooner and more frequently than the females.  More recently Sainte-Claire Deville observed that dogs, rams, and bulls, when isolated, first became restless and dangerous, and then acquired a permanent state of sexual excitement, not obeying the laws of heat, and leading them to attempts to couple together; the presence of the opposite sex at once restored them to normal conditions.[3] Bombarda of Lisbon states that in Portugal it is well known that in every herd of bulls there is nearly always one bull who is ready to lend himself to the perverted whims of his companions.[4] It may easily be observed how a cow in heat exerts an exciting influence on other cows, impelling them to attempt to play the bull’s part.  Lacassagne has also noted among young fowls and puppies, etc., that, before ever having had relations with the opposite sex, and while in complete liberty, they make hesitating attempts at intercourse with their own sex.[5] This, indeed, together with similar perversions, may often be observed, especially in puppies, who afterward become perfectly normal.  Among white rats, which are very sexual animals, Steinach found that, when deprived of females, the males practise homosexuality, though only with males with whom they have long associated; the weaker rats play the passive part.  But when a female is introduced they immediately turn to her; although they are occasionally altogether indifferent to sex, they never actually prefer their own sex.[6]

With regard to the playing of the female part by the weaker rats it is interesting to observe that Fere found among insects that the passive part in homosexual relations is favored by fatigue; among cockchafers it was the male just separated from the female who would take the passive part (on the rare occasions when homosexual relations occurred) with a fresh male.[7]

Homosexuality appears to be specially common among birds.  It was among birds that it attracted the attention of the ancients, and numerous interesting observations have been made in more recent times.  Thus Selous, a careful bird-watcher, finds that the ruff, the male of the Machetes pugnax, suffers from sexual repression owing to the coyness of the female (the reeve), and consequently the males often resort to homosexual intercourse.  It is still more remarkable that the reeves also, even in the presence of the males, will court each other and have intercourse.[8] We may associate this with the high erotic development of birds, the difficulty with which tumescence seems to occur in them, and their long courtships.