Category: Sociality

[Skip to list of Topics for this Category →]

Many organisms show some form of social behaviour or cooperative activity, ranging from simple bacterial associations in biofilms to the highly complex organisation of eusocial insects. Sociality may serve a reproductive, protective or foraging function.

When the cooperation of individuals improves the chances of capturing prey and results in the food intake of an individual being higher than if hunting solitarily, animals hunt in groups. Cooperative hunting is most familiar from mammals, such as lions, hyenas, wolves, chimpanzees, bottlenose dolphins and orcas. However, it has also evolved in some birds (e.g. Harris' hawks, pied currawongs), fish, insects and spiders. Young of the subsocial spider Amaurobius ferox capture prey ten times their size in a coordinated team effort. Usually, members of the same species hunt cooperatively, but there are a few spectacular examples involving different species. Dolphins indicate the presence of fish swarms to fishermen and groupers hunt together with moray eels in a highly coordinated fashion, initiated by a visual signal from the grouper.

While some animals occur in groups only temporarily (such as insect-eating non-migratory birds that switch to a diet of patchily distributed seeds and accordingly flock together during the winter), others show a permanent social organisation, where different types of societies can be distinguished. Matriarchal societies can be found in elephants, where the matriarch with her knowledge of the territory is vital to the survival of the family clan, but also in sperm whales. Fission-fusion societies that show a mixture of fluidity and stability have evolved repeatedly as well, for example in elephants, dolphins, chimpanzees and some New World Monkeys.

One of the most striking convergences concerns eusociality, an advanced and complex social system that is characterised by reproductive castes, i.e. reproductive division of labour with one or several fertile queens and sterile individuals (e.g. workers). Approximately 13,000 species are truly social, and there are at least 20 independent evolutionary origins of eusociality. The most important eusocial animals, in terms of numbers as well as ecological significance, are hymenopteran insects (ants, bees and wasps). Eusociality confers many evolutionary advantages, and is clearly why these groups are so successful. Almost 9,000 species of ant are eusocial, and amongst the most striking social arrangements are those found in the army ants. They are permanently nomadic, temporarily forming bivouacs but no permanent nest, and act as highly co-ordinated units performing carnivorous raids. Equally remarkable is the independent evolution of agriculture in the attine ants (which is also observed in many other arthropods, e.g. termites and ambrosia beetles). The complex eusocial organisation of the ants unsurprisingly includes many associated aspects of activity that show evolutionary convergence, such as quorum sensing, stridulation, silk production and tool making.

Apart from hymenopterans, also other insects are eusocial, namely termites, aphids, thrips and barkbeetles. Termites are only distantly related to ants and in fact evolutionarily very close to the cockroaches. A key factor in the evolution of eusociality is that termites produce hexamerins, which affect key growth hormones (e.g. juvenile hormone) and help to regulate which caste type (e.g. worker or soldier) each individual develops into. As eusocial forms the aphids are interesting not only because of the well-known production of a soldier caste. Soldiers have evolved multiple times and are typically clonal and equipped with powerful claws or stylets (and in one group even horns). A major difference between aphids and other eusocial insects is that many aphid groups live in the open and not in nests. Some aphids, however, are protected because they live in plant galls (as do e.g. thrips).

Interestingly, outside the insects eusociality is only found in two other groups, crustaceans (alpheid shrimps of the genus Synalpheus) and mammals (naked mole rats and Damaraland mole rats). The sponge-dwelling alpheid shrimps exhibit many of the hallmarks of eusocial organisation, diagnostically a single reproductive female and large numbers of non-reproductive individuals. In addition, they show effective co-ordinated defence indicating social communication. Their eusociality contributes to the observed rise in dominance over other crustacean groups. The burrowing mole rats live in underground colonies with a dominant female suppressing reproduction of all other females via latrine pheromones. Although the well-known meerkats are highly social, they cannot be considered eusocial as some significant mating occurs outside the dominant pair.

Social play is the hallmark of the most intelligent animal species, and there is a striking convergence between birds and mammals, with a one-to-one correspondence to the four principal categories of play (chasing, fighting, invitation and object play). While highly characteristic of young mammals, only those birds with complex cognitive abilities (namely crows, hornbills and parrots, particularly kea and kakapo) engage in social play.

Go to the top of the page

Topic Title Teaser text Availablity
Agriculture in beetles

Think of weevils and most likely you'll think of spoiled food. But some weevils have turned to farming...

Eusociality in alpheid shrimps

A group of coral-dwelling shrimps, the alpheids, have not only evolved eusociality, but managed it several times independently.

Not Available
Sociality in mole-rats and meerkats n/a Not Available
Co-operative hunting n/a Not Available
Intelligence and cognition in birds

House sparrows are known to gain access to shopping malls by flying in front of sensors that operate sliding doors, whilst herons have been shown to be adept fishers using baits and lures.

Bacterial communication and co-operation

Interesting convergences between bacteria and eukaryotes include aspects of communication linked to quorum sensing and enhanced cooperative activity in terms of formation of biofilms, mass attack on prey and dispersal.

Not Available
Eusociality in aphids

A soldier caste has evolved in aphids multiple times. They are typically clonal and equipped with powerful claws or stylets, and in one group even horns.

Not Available
Eusociality and agriculture in termites

Distinct hexamerins affect key growth hormones and help to regulate which caste type (e.g. worker or soldier) each individual develops into.

Not Available
Eusociality in arthropods and mammals

Eusociality is most familiar in the insects, where it has evolved several times, notably in bees, wasps, ants and termites, as well as in thrips and aphids.

Not Available
Eusociality and communication in bees and wasps

The feature of bee communication that has attracted the most attention is the famous bee “dance” that relays information concerning location of productive areas for gathering nectar, pollen or water.

Not Available
Beetles: insights into convergence

The beetles are probably the most diverse animal group on earth, so it is not at all surprising that they provide many fascinating insights into convergence.

Agriculture in ants: leaf-cutters (attines) and non-attines

In some species, special squads leave the nest early each day, ascend the tree-trunks and then spend hours cutting out pieces of leaf that are dropped to other units on the ground.

Eusociality and organisation in (army) ants

Army ants are permanently nomadic, and act as highly co-ordinated units that can form long files or fan out across the forest floor in search of prey.

Not Available
Slavery n/a Not Available
Ants: insights into convergence

Trap-jaws, silk and agriculture – just a few examples of convergence in the arguably most successful group of insects, the ants…

Crustaceans: insights into convergence

Whilst predominantly marine, quite a number of crustaceans have invaded freshwater habitats and even more interestingly a few demonstrate terrestrialization, effectively freeing themselves from their aquatic ancestry.

Fission-fusion societies

Fission-fusion societies has evolved repeatedly and are found, for example, in the elephants, dolphins, chimpanzees, as well as some New World Monkeys.

Not Available
Elephant response to death

Elephants are extremely unusual in their reaction to the dying and death of their compatriots, which includes attempts at resuscitation and grieving.

Not Available
Elephants: senses, intelligence and social structure

There is evidence that elephants are sensitive to seismic communication, with the large pads of the feet and the trunk tip capable of picking up vibrations transmitted through the ground.

Not Available
Parental care in vertebrates, echinoids, molluscs and brachiopods

The independent evolution of parental care is far more widespread than birds and mammals, extending as far as molluscs and echinoderms!

Not Available
Play in birds, mammals and octopus

Social play is the hall-mark of the most intelligent of this planet’s species, and there is a particularly striking convergence between birds and mammals.

Not Available