Harmony and Conflict in the Living World - Alexander F. Skutch [38]
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less members of their community, including the egg-producing females, the larvae, and sometimes also the males. And who would begrudge them such small delights?
Among the attractions that bring animals together, we must not overlook the communal roost, which as night approaches draws to a central point, often in tremendous numbers, birds that during the day have been widely scattered in smaller groups or singly. The roosts of such birds as starlings, pigeons, swallows, crows, and others are too well known to need description here. Often birds of a number of species sleep close together in a clump of tall bamboos or a high stand of grass or reeds. In inclement weather, many individuals of a species that is usually less gregarious may crowd into a cavity that offers some protection. In the western United States, O. A. Knorr (1957) found as many as a hundred and fifty Pygmy Nuthatches lodging in an old pine trunk that contained several holes, at least one hundred of them in the same cavity. In the Costa Rican mountains, during the season of chilling rainstorms, I once, to my great delight, watched sixteen Prong-billed Barbets enter a hole in a tree so small that they must have slept in layers. Yet, when nesting, these barbets are highly territorial (Skutch 1989).
Finally, we cannot lightly dismiss the desire for companionship, divorced from any purely utilitarian motive, as a factor that draws individuals together, at least among the higher animals. Deprived of companions of their own species, animals sometimes become closely attached to an individual of some very different species. W. H. Hudson told of a lone swan that sought the company of a horse. Such incongruous partnerships as that of a dog and a deer, a cat and a rabbit, or a crow and an owl, have been so frequently recorded in the annals of natural history that it seems superfluous to elaborate the point.
It will be noticed that in the foregoing discussion of the social bonds nothing was said about sex. The omission is deliberate. Sex itself is not a cohesive but a disruptive factor in animal life. As already noted, gregarious mammals and birds, which through the long annual interval of sexual quiescence have lived together amicably, become mutually antagonistic as their reproductive urges
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awaken; coursing through their veins like some subtle venom, the sexual hormones make implacable enemies of erstwhile companions. Sex, in itself, forges no lasting bonds even between individuals of opposite sexes. Unless sexual partners are held together by some shared occupation or interest, such as caring for their offspring, or by personal liking or attachment not dependent upon primary sexual activity, male and female separate and go their own ways after the exhaustion of their erotic ardor. This applies to humans no less than to the rest of the animal kingdom, the chief exceptions being species in which a degenerate male lives permanently attached to the female in parasitic dependence, as in angler fish. Failure to recognize these truths has led certain anthropologists to attribute to the absence of an annual interval of sexual quiescence in humans a role in human social development that does not belong to it. Only indirectly, as the necessary prelude to the generation of offspring whose care unites the two parents in a shared activity, has sex contributed importantly to sociality in people and other animals.
Cooperation in Nesting and Attending Young
Sea birds of many kinds may be constrained to nest colonially by the paucity of islets or forbidding cliffs where alone they find adequate protection for their eggs and young. The massing of nests of gulls,