The Old World monkeys or Cercopithecidae are a group of primates, falling in the superfamily Cercopithecoidea in the clade (or parvorder) of Catarrhini. The Old World monkeys are native to Africa and Asia today, inhabiting a range of environments from tropical rain forest to savanna, shrubland and mountainous terrain, and are also known from Europe in the fossil record. However, a (possibly introduced) free-roaming group of monkeys still survives in Gibraltar (Europe) to this day. Old World monkeys include many of the most familiar species of nonhuman primates, such as baboons and macaques.
The vervet monkey (Chlorocebus pygerythrus), or simply vervet, is an Old World monkey of the family Cercopithecidae native to Africa. The term "vervet" is also used to refer to all the members of the genus Chlorocebus. The five distinct subspecies can be found mostly throughout Southern Africa, as well as some of the eastern countries. Vervets were transported to the islands of Barbados, Saint Kitts, and Nevis in conjunction with the African slave trade. These mostly vegetarian monkeys have black faces and grey body hair color, ranging in length from about 19 in (50 cm) for males to about 16 in (40 cm) for females.
In addition to very interesting behavioral research on natural populations, vervet monkeys serve as a nonhuman primate model for understanding genetic and social behaviors of humans. They have been noted for having human-like characteristics, such as hypertension, anxiety, and social and dependent alcohol use. Vervets live in social groups ranging from 10–50 individuals, with males changing groups at the time of sexual maturity. The most significant studies done on vervet monkeys involve their communication and alarm calls, specifically in regard to kin and group recognition and particular predator sightings.