Concept
In ethology, a fission–fusion society is one in which the size and composition of the social group change as time passes and animals move throughout the environment; animals merge into a group (fusion)—e.g. sleeping in one place—or split (fission)—e.g. foraging in small groups during the day. For species that live in fission–fusion societies, group composition is a dynamic property. The change in composition, subgroup size, and dispersion of different groups are 3 main elements of a fission-fusion society. This social organization is found in several primates, elephants, cetaceans, ungulates, social carnivores, some birds and some fish. Fission-fusion societies occur among many different species of primates (e.g. chimpanzees, orangutans, and humans), elephants (e.g. forest elephants, African elephants), and bats (e.g. northern long-eared bats). The change in composition, subgroup size, and dispersion of different groups are 3 main elements of a fission-fusion society. Chimpanzees often form smaller subgroups when travelling for longer periods at a time in between each food patch. When obtaining food, the size of subgroups can change depending on how much food is available and how far away the food may be. If food is worth retrieving due to little travel costs, subgroup size will enlarge. So among chimpanzees, the abundance of food and how dense it may be are factors that contribute to the changes of subgroup sizes. Orangutans are one type of primates that model individual-based fission-fusion. Travel parties are established among this species inhabiting specifically in a Sumatran forest, and there are several benefits. Mating opportunities are a large benefit of grouping, as parties are most substantial during high mating activity. Infant socialization also contains benefits as well as costs, due to their needs to be cared for. Females are required to carry their infants, and those with infants of mid-size experience greater costs than those of small sizes. Carrying a small infant does not require much, and they become less dependent as they begin to wean.