Callithrix geoffroyi
Geoffroy's marmoset

Geoffroy's marmosets (Callithrix geoffroyi) are found in southeastern Brazil. They inhabit the state of Espirito Santo and the forested eastern and north-eastern part of the state of Minas Gerais. They are found as far north as the Rio Jequitinhonha and Aracuai and south to near the state border of Espirito and Rio de Janeiro. The population south of Rio Jequitinhonha originated from animals released near the river's mouth in 1975. This population has since spread eastward. A hybrid population of Callithrix penicillata x C. geoffroyi has been found in the Serra da Piedade along the Rio Piracicaba. (Rylands and Mendes, 2008)

Geoffroy's marmosets inhabit secondary lowlands and sub-montane forest, evergreen, and semideciduous forest, forest edge and dry forest patches. They are generally found at an elevation of between 500 and 700 m, but can be found as high as 800 m. (Rowe, 1996; Rylands and Mendes, 2008)

Geoffroy's marmosets are small primates, only about 200 mm in length, with a tail of about 290 mm. Females tend to weigh around 190 g, while males range from 230 g to 350 g. The body is predominately dark or blackish brown. The tail is ringed with gray and black bands. Adults have white foreheads, cheeks, temples and throats. Adults also have tufts of black fur in front of their ears. Juveniles differ from adults in that they lack both the ear tufts and white markings around the face. Juveniles begin to grow their ear tufts at an age of about 2 weeks, and have full adult markings by the age of 5 months. (Rowe, 1996; Stevenson and Rylands, 1988)

The dominant male and female in each group of Geoffroy's marmosets form a monogamous pair bond. Only this pair will breed. Dominant behavior of the breeding female will halt ovulation in other females in the group. This process may be aided by pheromones produced in the scent glands of the dominant female. As a result, subordinate females cannot reproduce while they remain with the group. Such hierarchy is less evident among males. Usually only one male mates with the breeding female, but polyandry (usually rare among mammals) has been observed under certain circumstances. (Wakenshaw, 1999)

Pre-copulatory courtship usually begins with sniffing each other's muzzles and genitalia, as well as marking objects, licking, grooming and huddling. These behaviors are also seen in post-copulatory courtship. These behaviors increase as the female reaches estrus. (Wakenshaw, 1999)

Female estrus cycles vary from 14 to 21 days. Should a female become pregnant, the gestation lasts about 140 to 148 days. Parturition may take up to an hour. Usually twins are born, but sometimes singletons or triplets occur. The male will assist with the birth by licking the babies before giving them to the mother. Other family members may help to eat the placenta. Post-partum estrus occurs 2 to 14 days after giving birth. Young are weaned by 5 or 6 months and reach sexual maturity between 15 and 18 months. (Wakenshaw, 1999)

A female Geoffroy's marmoset will suckle both of her twins at the same time, until the young are weaned. For the first week after young are born, the father carries the babies exclusively. After this, the male will still be the primary carrier, but all members of the family participate in carrying the young. Older siblings assist in the rearing of the younger siblings, by which they learn skills essential to raising their own young in the future. Females primarily provide milk for their young. (Wakenshaw, 1999)

Geoffroy's marmosets generally live about 10 years. (Richardson, 2007)

Geoffroy's marmosets are diurnal, arboreal, and scansorial. They live in family groups of between 8 and 10 individuals. During the wet season, Geoffroy's marmosets spend 32.1% of their time resting, 21% feeding, 20% moving, 14% foraging, 13% gouging (for gum), and 3% doing other activities such as playing, grooming, scent marking and vocalizing. During the dry season, time spent resting drops to 17.8% and time spent foraging increases to 20.6%. Geoffroy's marmosets are reported to follow swarms of army ants in order to catch the insects flushed out by the ants. (Rowe, 1996)

Groups defend a home range of between 10 ha and 40 ha. (Rylands and Mendes, 2008)

Geoffroy's marmosets make alarm calls when they perceive a threat. They have also been observed scent marking. Allogrooming has been observed too, and is thought to contribute to calming the group down after a threat has passed. (Caine, 1998; Passamani, 1998)

Geoffroy's marmosets are omnivorous, eating mostly fruit, insects, and plant gums. They also eat flowers, nectar, frogs, snails, lizards, and spiders. These small primates are able to gouge into tree trunks, branches, and vines to obtain gum. (Passamani, 1998; Rowe, 1996; Rylands and Mendes, 2008)

Members of the Family Callitrichidae, including Geoffroy's marmosets, are highly affected by predation, perhaps to the highest degree of any primate. Field reports indicate that monitoring for predators is a high priority in the lives of marmosets. Groups of C. geoffroyi respond to predator threats by increasing rates of vigilance and decreasing rates of play and foraging. Members of groups share the task of monitoring by rotating occupation of the best look-out point. Geoffroy's marmosets have a variety of responses to raptors, snakes, and felids as well as other predators. Wild Geoffroy's marmosets react to predators with combinations of monitoring, alarm calls, mobbing, fleeing, and freezing. (Caine, 1998)

Geoffroy's marmosets prey on a variety of small vertebrates and invertebrates and provide prey for larger predators. (Passamani, 1998; Rowe, 1996; Rylands and Mendes, 2008)

Geoffroy's marmosets are occasionally captured for the pet industry. (Rylands and Mendes, 2008)

There are no known adverse effects of Geoffroy's marmosets on humans.

Geoffroy's marmosets are considered "Least Concern" by the International Union for Conservation of Nature. The population trend for this species is classified as stable. However, widespread destruction is causing their populations to decline. The range of C. geoffroyi was once throughout the Brazilian Atlantic forest, but only about 1% to 5% of this habitat remains. For example, less than 6.8% of the Atlantic forest remains in the state of Minas Gerais. However, C. geoffroyi is considered relatively abundant and inhabits many protected areas. For this reason, their rate of population decline does not warrant a threatened listing. In 1982, Russell Mittermeier recommended that C. geoffroyi be listed as endangered, but studies conducted in 1991 found them to be locally abundant, if patchily distributed. In 1994, 1996, and 2000 C. geoffroyi was listed as vulnerable by the IUCN. Today, it is not considered under serious threat. (Passamani, 1998; Rylands and Mendes, 2008)

Callithrix geoffroyi was declared a separate species in 1988. It was previously considered to be a subspecies of Callithrix jacchus. (Rowe, 1996)