Presociality
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Presociality is a phenomenon in which animals exhibit more than just sexual interactions with members of the same species; however, they fall short of qualifying as eusocial. That is, presocial animals can display communal living, cooperative care of young, or primitive reproductive division of labor, but they do not display all of the three essential traits of eusocial animals, those being
- There are many generations that are alive.
- There is division of labour. Some animals may be specialised for a certain function. Some animlas may be sterile.
- The older animals cooperate to care for the young.
Presocial behavior is much more common in the animal kingdom than complete eusociality. Examples include canines that live in packs, numerous insects, especially hymenoptera, humans, many birds, chimpanzees, and many other animals that display social behavior.
Some sociobiologists further categorize types of presociality:
- Subsocial: parents interact with young
- Parasocial: individuals of the same generation live in a single, cooperative dwelling and interact with each other
- Communal: each individual care exclusively for her or his own young
- Quasisocial: individuals care cooperatively for all brood; however, all members of the colony are reproductive
- Semisocial: a limited group of individuals reproduces, yet the arrangement is not quite eusocial. Adult generations might not overlap, the reproductive dominance might be temporary, or some other requirement is not met.
The path to each of these stages of sociality is highly varied between different groups of animals. Sociality itself can be seemingly contrary to the theory of Darwinian evolution. Darwin saw the phenomenon as a serious challenge for his theory to overcome. However, modern sociobiology has been able to explain many cases of social behavior.
Among the Vespidae, it is thought that the pressures of predators and parasites selected subsocial behavior; that is, when the mother wasp stays in her brood cell to watch over her larva, it becomes less likely that parasites will be successful in preying on the nest. Other pressures can force the evolution of presociality. A lack of resources available to pack-wolves makes it possible to raise only one litter, even with the aid of the pack. This forces reproduction to be suppressed in all but the alpha-male and -female; this way, the non-reproducing members of the pack can focus all of their care on one litter rather than several unsuccessful ones.
[change] References
- Ross, Kenneth G and Robert W. Matthews. 1991. The Social Biology of Wasps. Comstock. Ithaca, New York.
