to the juvenile marmosets. Members of the group, usually female, may even put off their own reproduction through a temporary cessation of ovulation in order to care for the offspring of others in the group. The ideal number of caregivers for an infant marmoset has been shown to be around five individuals. Caregivers are responsible for finding food for the infants as well as helping the father watch for predators. Pygmy marmosets are non-seasonal breeders and usually gives birth to twins once or twice a year. However, single births occur 16% of the time and triplet births 8% of the time. The pygmy marmoset is usually monogamous though there is some variation within the species in terms of breeding systems. Polyandry also occurs as male marmosets are responsible for carrying the infants on their backs. Having a second male to carry the offspring can be beneficial as marmoset litters are often twins and decreases the cost to any particular male. The daily range of pygmy marmosets, however, is relatively small, which decreases the rate of polyandry. Male and female pygmy marmosets show differences in foraging and feeding behavior, although male and female dominance and aggressive behavior varies within the species. Males have less time to search out food sources and forage due to the constraints of their infant caring responsibilities and predator vigilance. Without an infant to carry, female pygmy marmosets have greater freedom to forage, giving them an apparent feeding priority. This priority may serve to compensate mothers for the energetic costs of carrying and lactating for two offspring at a time. However, the fact that feeding priority is also given to females without offspring weakens the argument. Instead, female feeding priority may have evolved through sexual selection. Females may choose mates who invest more time in infant care and predator vigilance. Such males have less time to look for food, allowing the female feeding priority. Communication Pygmy marmosets are well known for their communication abilities including an intricate system of calls. The trill is used during feeding, foraging, and when travelling and the group is close together. The J-call is a series of fast notes repeated by the caller and is used at medium distances. Both calls are used as contact calls. The long call is used when the group is spread out over distances greater than ten meters or in response to a neighboring group. The pygmy