White-Headed Marmoset
They are also known as the tufted-ear marmoset, Geoffroy's marmoset, or Geoffrey's marmoset. They are small primates measuring about 7.8 inches. Females weigh only 0.4 lb, while males weigh 0.5–0.8 lb. Their tails are longer than their body length, measuring at 11 inches. Their typical lifespan in the wild is about 10 years. They are mostly black and dark brown in colour. Their tail is lightly ringed with grey and black bands. Adults have white heads, cheeks, and throats.
Adults also have black tufts of fur by their ears.​Infants lack ear tufts and white markings around their face. At about two weeks of age, juveniles begin to grow their ear tufts and have full adult markings by 5 months. Marmosets (and tamarins) are distinguished from other New World monkeys by their small size and modified claws, rather than nails, on all digits except their big toe. They also possess two molar teeth on each side of the jaw rather than three.
Habitat
The species is endemic to Brazil. They are present in the state of Espirito Santa and in the forested eastern and northeastern regions of Minas Gerais, extending north as far as the Rios Jequitinhonha and Aracuai, as well as south to near the state border of Espirito Santo and Rio de Janeiro. The population in the south of Rio Jequitinhonha was introduced there in 1975. The population has since spread eastward. They live in lowland forests, sub-montane forests, and dry forest patches in desert scrub. They inhabit a wide variety of habitats such as dense forests, semi-deciduous forests in the Atlantic forest biome, and deciduous forests in the Caatinga biome. They are tolerant to changes and environmental disturbances; thus, they can be considered a well-adapted species to anthropogenic environments, where there is human activity.
Diet
They are omnivorous, eating fruits, flowers, nectar, and insects. They will also eat small animal prey such as snails, lizards, and frogs. Marmosets have behavioural and morphological adaptations for gouging tree trunks to extract plant exudates such as gum and sap. Their claws allow them to cling onto the side of trees and gnaw off the bark with their incisors, then scoop out the gum or sap with their fingers.
Breeding
The dominant male and female in a group form a monogamous bond; only this pair breeds. Reproduction in other adult female troop members is suppressed by pheromones produced by the scent glands of the dominant breeding female. This leads to a delay in reproduction in subordinate females for as long as they remain within the group. Theories suggest that female reproduction is suppressed so that those other troop members are available to assist with childcare. Courtship begins with sniffing each other, marking objects, huddling, and grooming. These behaviours start to increase as the female reaches estrus. Twins are usually born, but sometimes a single infant or triplets may occur. The father assists with the birth and licks the babies, then gives them to the mother. Other family members may eat the placenta. Infants nurse for 5–6 months. Unlike many other primates, a female white-headed marmoset feeds both her infants at the same time. Within the first week of being born, the father carries the twins exclusively, only handing them over to the mother to nurse. The father remains the primary carrier of the infants; however, after the first week, all members of the family participate in carrying the young. Older siblings also assist in taking care of the young. This teaches the older siblings essential skills they need in caring for their future offspring.
Population
According to the IUCN Red List, they are classed as Least Concern(LC). Their current population trend is decreasing. The total population size is not known, but it is inferred that the number of mature individuals is greater than 10,000. They have an average size group ranging from 3 individuals.
Threats
The major threats identified were rural settlements, agriculture, livestock, deforestation, isolation, habitat reduction and expansion of forestry. Although considered an adaptable species, populations are declining because of widespread destruction of the Atlantic forest in the states of Minas Gerais and Espírito Santo. Less than 6.8% of the original area of Atlantic forest remains in the state of Minas Gerais. It has remained locally abundant and concluded that the species is not seriously threatened at the present time. It is occasionally hunted for pets.
Conservation
This species occurs in a number of protected areas:
Minas Gerais
Serra do Cipo National Park (33,800 ha)
Fazenda Córrego de Areia Reserve (60 ha) (privately owned)
Espirito Santo
Córrego Grande Biological Reserve (1,504 ha)
Córrego do Veado Biological Reserve (2,392 ha)
Sooretama Biological Reserve (27,943 ha)
Comboios Biological Reserve (833 ha)
Duas Bocas State Reserve (2,910 ha)
Linhares Forest Reserve (21,787 ha)
Goitacazes Forest Reserve (1,400 ha)
Santa Lucia Biological Station (350 ha)
Fazenda São Joaquim Reserve (Klabin Reserve) (1,505 ha)
Bahia
Porto Seguro Forest Reserve (6,069 ha)
Pau Brasil Experimental Station (900 ha)
Gregório Bondar Experimental Station (710 ha)
Santa Catarina
Córrego Grande Ecological Park (21,3 ha).
This species is listed on Appendix II of CITES.