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Gray wolves hunting in a presocial pack encircle an American bison.

Sociality is the degree to which individuals in an animal population tend to associate in social groups and form cooperative societies.


This wasp behaviour evidences the most fundamental characteristic of animal sociality: parental investment. Parental investment is any expenditure of resources (time, energy, social capital) to benefit one offspring. Parental investment detracts from a parent's capacity to invest in future reproduction and aid to kin (including other offspring). An animal that cares for its young but shows no other sociality traits is said to be subsocial.


Solitary animals, such as the jaguar, don't associate except for courtship and mating. If an animal taxon shows a degree of sociality beyond courtship and mating, but lacks any of the characteristics of eusociality, it is said to be presocial.[3] Presociality is much more common than eusociality.


Entomologist Charles D. Michener published a classification system for presociality in 1969, building on the earlier work of Suzanne Batra (who coined the words eusocial and quasisocial in 1966).[4][5] Michener used these terms in his study of bees, but also saw a need for additional classifications: subsocial, communal, and semisocial. In his use of these words, he did not generalize beyond insects.

E. O. Wilson later refined Batra's definition of quasisocial.[6][page needed]



Solitary but social[edit]

See also: Solitary animal

Solitary-but-social animals forage separately, but some individuals sleep in the same location or share nests. The home ranges of females usually overlap, whereas those of males do not. Males usually do not associate with other males, and male offspring are usually evicted upon maturity. Among primates, this form of social organization is most common among nocturnal, prosimian species. Some examples of solitary-but-social species are mouse lemurs, lorises, and orangutans.[7]


Sociobiologists place communal, quasisocial, and semisocial animals into a meta-class: the parasocial. What parasocial taxa have in common is that they socialize in a single, cooperative dwelling.[3]

Here is how communal, quasisocial, and semisocial taxa differ: In a communal group, adults cohabit in a single nest site, but they each care for their own young. Quasisocial animals, however, additionally share the responsibilities of brood care.

Quasisocial behaviour has been observed in some Hymenoptera and spider taxa,[8] as well as in some other invertebrates.[3]



Bees almost completely cover a honeycomb suspended from a tree branch.
Giant honey bees cover the honeycomb of their hive.

Eusocial societies have overlapping adult generations, cooperative care of young, and division of labor. However, in some animal species the division of labour is more flexible than in others. An individual's duty is dictated by caste, but one's caste may change.

For example, a queen bee can become a worker bee, and a worker bee can become a queen bee.[3][9] The individual has a social role, but that role is not codified in the shape of the organism (its morphology). However, when organisms in a species are born with physical characteristics specific to a caste, and that caste never changes in the life of the organism, this exemplifies the highest acknowledged degree of sociality. Only two orders in the animal kingdom include highly eusocial taxa: Hymenoptera (ants, bees, sawflies, and wasps) and the infraorder isoptera (termites). Eusocial species that lack this criterion of morphological caste differentiation are said to be primitively eusocial.[3]

Mammalian examples include the naked mole rat and the Damaraland mole rat (Heterocephalus glaber & Fukomys damarensis, respectively),[10] two species of vertebrates that are diploid and highly inbred. Usually living in harsh or limiting environments, these mole rats aid in raising siblings and relatives born to a single reproductive queen. However, this classification is controversial owing to disputed definitions of 'eusociality.' A study conducted by O’Riain and Faulkes in 2008 suggests that due to regular inbreeding avoidance, mole rats sometimes outbreed and establish new colonies when resources are sufficient.[11] Thus, it is uncertain whether mole rats classify as true eusocial organisms, since their social behavior depends largely on their resources and environment.

Eusociality has also arisen among some crustaceans that live in groups in a restricted area. Synalpheus regalis, parasitic shrimp that rely on fortress defense and live in groups of closely related individuals in tropical reefs and sponges,[12] live eusocially with a single breeding female and a large number of male defenders, armed with enlarged snapping claws. As with other eusocial societies, there is a single shared living space for the colony members, and the non-breeding members act to defend it.[13]

Comparison of sociality classifications[edit]

Degree of sociality Parental investment Members of only one adult generation and their young cohabit Cooperative care of young Reproductive division of labour Caste system Overlapping adult generations
Subsocial Yes No No No No No
Solitary but social Yes Sometimes No No No No
Communal Yes Yes No No No No
Quasisocial Yes Yes Yes No No No
Semisocial Yes Yes Yes Yes Yes No
Eusocial Yes No Yes Yes Yes Yes

See also[edit]


  3. ^ a b c d e Gadagkar, Raghavendra (September 1987). "What are social insects?" (PDF). IUSSI Indian Chapter Newsletter (International Union for the Study of Social Insects) 1 (2). 
  4. ^ Michener, C. D. (1969). "Comparative Social Behavior of Bees". Annual Review of Entomology 14: 299–342. doi:10.1146/annurev.en.14.010169.001503. 
  5. ^ Batra, S. W. T. (1966). "Social behavior and nests of some nomiine bees in India (Hymenoptera, Halictidæ)". Insectes Sociaux 13 (3): 145–153. doi:10.1007/BF02223020. 
  8. ^ Furey, R. E. (1998). "Two cooperatively social populations of the theridiid spider Anelosimus studiosus in a temperate region". Animal behaviour 55 (3): 727–735. doi:10.1006/anbe.1997.0648. PMID 9515053. 
  9. ^ Cf. Gyne
  10. ^ Burda, H. Honeycutt; Begall, S.; Locker-Grutjen, O; Scharff, A. (2000). "Are naked and common mole-rats eusocial and if so, why?". Behavioral ecology and sociobiology 47 (5): 293–303. 
  11. ^ O'Riain, M.J.; Faulkes, C. G. (2008). "African mole rats: eusociality, relatedness and ecological constraints". Ecology of Social Evolution: 207–223. 
  12. ^ Duffy, J. Emmett; Cheryl L. Morrison and Ruben Rios (2000). "Multiple origins of eusociality among sponge-dwelling shrimps (Synalpheus)". Evolution 54 (2): 503–516. doi:10.1111/j.0014-3820.2000.tb00053.x. PMID 10937227. 
  13. ^ Duffy, J. E (1998). "On the frequency of eusociality in snapping shrimps (Decapoda: Alpheidae), with description of a second eusocial species". Bulletin of Marine Science 63 (2): 387–400.