Social Behavior

Social behavior can be defined as any kind of interaction between two or more animals, usually of the same species. Some species, like the bonobos in Figure 44-12, spend the majority of their lives in social groups.

Social Groups

Social groups have evolved in the animal kingdom because there are benefits to living in a group. These benefits can include protection from predators and more success in foraging. For example, fish on the outer edges of a school assume most of the danger of predation. The fish swimming on the edges shift constantly, so most individuals are not exposed to danger for a long time. Lions hunting cooperatively can bring down large prey much more efficiently than lions hunting alone.

There are also disadvantages to living in a social group. For example, there is often increased competition for food, mates, and other resources. The risk of spreading disease is also higher within a social group than it would be among a population of nonsocial animals. One species that exemplifies both the benefits and disadvantages of social groups is the blue-gill sunfish. During mating season, blue-gills nest close together. The larger number of individuals helps provide protection against predators. However, disadvantages include competition during courtship, theft of eggs by non-breeding males, and possibly transmission of disease.

Altruism

Occasionally, one member of a social group acts in a way that benefits other members of the group while putting the individual at a disadvantage. This type of behavior is called altruism (AL-troo-ism). One example of altruism can be seen in the ground squirrel found in North America. These animals live in large colonies. If one member of the colony sees a predator, it will give a high-pitched alarm call, as shown in Figure 44-13. This call warns other members of the colony to hide while putting the animal that calls at risk.

Another example of altruism occurs in animal societies in which the workers are sterile. Bees, ants, termites, and naked mole rats are all examples of animals that live in this type of society. Usually, members of a society are related to each other and share a large proportion of their genes. Therefore, helping a relative survive increases the chance that the genes an individual shares with that relative will be passed to the next generation. This type of natural selection is called kin selection.

figure 44-12

Bonobos are a species of ape closely related to chimpanzees. Bonobos have a highly complex and unusually peaceful social system.

figure 44-12

Bonobos are a species of ape closely related to chimpanzees. Bonobos have a highly complex and unusually peaceful social system.

figure 44-13

A ground squirrel gives a piercing warning call that signals the presence of a predator.

figure 44-13

A ground squirrel gives a piercing warning call that signals the presence of a predator.

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