Vervet Monkey social structure – alarm calls
Vervets live in multi-male/multi-female groups and exhibit female philopatry. They live in groups of seven to 76, but the minimum number of adults necessary to maintain a stable group is two.
Females remain in their natal groups throughout their entire life; therefore the core of the social group is closely related adult females and their dependent offspring. A linear dominance hierarchy exists within the group and high-ranking females and their close relatives (mothers, sisters, and daughters) are the most sought-after grooming partners and have preferential access to food resources .
With higher stores of body fat, females are less likely to experience amenorrhea induced by malnutrition and they are likely to have higher milk quality that contributes to faster infant growth and therefore decreased mortality in their larger infants, and decreased interbirth intervals .
Rank relationships between females can be seen when one adult female supplants another; when the higher-ranking female approaches the lower-ranking female, the one lower in rank moves away from the approaching female and is displaced. Females are supported by their relatives in agonistic interactions and form coalitions that last a lifetime. Daughters inherit the rank of their mothers because of social support given to their daughters even after they reach adulthood.
Vocal communication in vervets has been well studied because of their intricate system of predator-sensitive alarm calls. Vervets give separate, distinct vocalizations for certain predators that elicit predator-appropriate responses from their conspecifics. In the wild, leopards, martial eagles, and pythons pose serious predatory risks to vervets . Leopards crouch and pounce from the tall grass, eagles swoop down while flying and can use their talons to grab an infant off of a mother’s back, and pythons move through the grass and attack from the ground .
Alarm calls serve the purpose of alerting other group members to the presence of danger. When an adult vervet sees one of these predators and gives an alarm call, the rest of the group respond appropriately. When the leopard call is given, the monkeys run up into the trees, where they are safer from the ambush style of attack typical of big cats. When the eagle alarm call is sounded, vervets look to the sky and run into dense brush or low-lying bushes in order to hide from the swooping raptor . Finally, when the snake call is given, vervets respond by looking down around them; this response is appropriate because vervets often work as a group to mob dangerous snakes
Adult vervets properly alert group members to the potential predator while infant and juvenile vervets often misidentify predators and give inappropriate alarm calls. Though the infants are able to assign the suitable class of predator, for example giving an eagle alarm call when any bird flies over, they need to learn the appropriate context in which to give alarm calls. The vervet sounding the alarm call conveys information about the perceived threat and the other members of the group can interpret the call and respond appropriately. This form of semantic communication was long thought to be unique to humans and the other great apes, but researchers Dorothy Cheney, Robert Seyfarth, and Peter Marler effectively proved that vervets are capable of referential communication.