Sociality
Sociality describes animal grouping and cooperative behavior.
Sociality is the degree to which individuals in an animal population tend to associate in social groups and form cooperative societies, with the underlying inclination known as gregariousness. This behavior arises as a survival response to evolutionary pressures; for instance, a mother wasp that remains near her larvae reduces the likelihood of parasites consuming them, and biologists suspect that such pressures from parasites and other predators selected for this behavior in wasps of the family Vespidae. The most fundamental characteristic of animal sociality is parental investment, defined as any expenditure of resources—such as time, energy, or social capital—to benefit one’s offspring. This investment comes at a cost, detracting from the parent’s capacity to invest in future reproduction or aid to kin, including other offspring. An animal that cares for its young but exhibits no other sociality traits is termed subsocial. Animals that show a high degree of sociality are called social animals, and the highest recognized degree is eusociality, which involves overlapping adult generations, reproductive division of labor, cooperative care of young, and, in the most refined cases, a biological caste system. Social animals often possess relatively high cognitive ability; for example, social mammal predators like spotted hyenas and lions outperform non-social predators such as leopards and tigers at solving problems requiring innovation. Solitary animals, like the jaguar, associate only for courtship and mating. Taxa showing sociality beyond this but lacking eusocial characteristics are termed presocial, with presocial species being far more common than eusocial ones, though eusocial species have disproportionately large populations. The entomologist Charles D. Michener published a classification system for presociality in 1969, building on earlier work by Suzanne Batra, who coined the terms eusocial and quasisocial in 1966. Michener’s study focused on bees and introduced additional categories: subsocial, communal, and semisocial. E. O. Wilson later refined Batra’s definition of quasisocial. Subsociality, where parents care for young for some period, is widespread in the animal kingdom and has evolved independently many times among winged insects. Solitary-but-social animals forage separately but may share sleeping sites or nests, with female home ranges often
- field
- Sociobiology, Ethology
- known_for
- Classification of sociality levels from solitary to eusocial
- key_concepts
- Parental investment, subsociality, presociality, eusociality
- related_taxa
- Vespidae wasps, Hymenoptera, Blattodea, naked mole-rat, Damaraland mole-rat, Synalpheus regalis
Lore & Background
Sociality is a survival response to evolutionary pressures, such as the threat of parasites and predators, which has selected for behaviors like a mother wasp staying near her larvae to protect them. The most fundamental characteristic of animal sociality is parental investment, defined as any expenditure of resources—time, energy, or social capital—to benefit offspring, which reduces a parent's ability to invest in future reproduction or aid to kin. Animals that care for their young but lack other social traits are termed subsocial. The highest recognized degree of sociality is eusociality, which involves overlapping adult generations, reproductive division of labor, cooperative care of young, and, in refined cases, a biological caste system. Social animals often exhibit relatively high cognitive ability; for instance, social mammal predators like spotted hyenas and lions are better at solving innovative problems than non-social predators such as leopards and tigers. Taxa that show sociality beyond courtship and mating but lack full eusociality are called presocial. Charles D. Michener, building on Suzanne Batra’s earlier work, published a classification system for presociality in 1969, including categories such as subsocial, communal, and semisocial. Subsociality is common across the animal kingdom and has evolved independently many times among winged insects. Solitary-but-social animals forage separately but may share nests or sleeping sites, with overlapping female home ranges but not male ones; this organization is common among nocturnal strepsirrhine primates and tarsiers. Parasociality encompasses communal, quasisocial, and semisocial groups, all exhibiting parental investment and cooperative dwelling, with differences in brood care and reproductive caste systems.
Reader's Guide
The concept of sociality is central to understanding animal behavior and evolution. It ranges from solitary animals, such as the jaguar, which associate only for courtship and mating, to eusocial species like ants, bees, and termites, which exhibit overlapping generations, cooperative care, and reproductive division of labor. The classification system for presociality, developed by Charles D. Eusociality has evolved in several insect orders and has been observed in some crustaceans, such as Synalpheus regalis snapping shrimp. The debate over whether a species must have an irreversibly sterile caste to be considered eusocial remains unresolved, with implications for classifying mammals like naked mole-rats and even humans.
Did You Know?
- Sociality is a survival response to evolutionary pressures, such as parasites selecting for maternal care in wasps of the family Vespidae.
- The highest degree of sociality recognized by sociobiologists is eusociality, which includes overlapping adult generations, reproductive division of labor, and cooperative care of young.
- Solitary-but-social animals forage separately but may share nests or sleeping locations; examples include mouse lemurs, lorises, and orangutans.
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