White-Headed Marmoset, Callithrix geoffroyi (draft)
WHITE-HEADED MARMOSET
Callithrix geoffroyi
Geographic Distribution and Habitat
The white-headed marmoset is endemic to Brazil and can be found in the eastern coast states of Espirito Santo, Minas Gerais, and Bahia. They can live at altitudes of up to 4,179 feet (1,274 meters) and as low as 1,640 feet (500 meters) and can be found in submontane forests, deciduous forests, and densely forested areas. They are relatively tolerant of secondary forests—forests that have been felled and have since regrown, resulting in a more dense understory. While they adapt relatively well to ever-encroaching human pressures and disturbances, they remain significantly impacted by deforestation.
The white-headed marmoset has a home range of 24 to 100 acres (10-40 ha). A home range is the distance that the group may travel on a regular basis. Researchers point to their large home range, particularly when compared to their body size, as evidence of high-functioning cognitive abilities. In short, maintaining such a large home range requires exceptional memory and mind-mapping skills.
The white-headed marmoset is also known as the tufted-ear marmoset or Geoffrey’s marmoset. When referring to marmosets, there are two genera under that term—the Mico genus and the Callithrix genus. The white-headed marmoset is part of the Callithrix genus, which includes five other marmoset species: common marmoset (Callithrix jacchus), black-tufted marmoset (Callithrix penicillata), Wied’s marmoset (Callithrix kuhlii), the buffy-headed marmoset (Callithrix flaviceps), and the buffy-tufted marmoset (Callithrix aurita). All of these marmosets inhabit eastern Brazil, ranging from central to the northern coast.
Size, Weight, and Lifespan
The white-headed marmoset is a petite monkey measuring only about 8 inches in length (20 centimeters). Their tail adds another 11 inches (29 centimeters). They are generally considered sexually monomorphic, which means their size and physical characteristics do not vary depending on the sex of the individual. They weigh 9 to 13 ounces (250 to 380 grams). Their lifespan is around 10 years.
Appearance
The white-headed marmosets’ pelage ranges from black to gray, often giving a salt-and-pepper appearance from the chest to the arms. Their backs are also black and gray, but they have highlights of golden orange on their backs. Their long tails are black with light gray rings that extend down the length of the tail. Their face and necks are white, and they have long black tufts of hair protruding from the sides of their head.
Unlike other South American monkeys, the white-headed marmoset, like all marmosets, have claws on most of their fingers, rather than nails. The exception is the big toe, which has a toenail. The claws are a special adaptation that helps with their arboreal lifestyle and access to their dietary preferences.
Diet
The white-headed marmoset has a notorious sweet tooth. These small monkeys enjoy fruit, flowers, nectar, sap, and tree gums. They also eat insects, small amphibians, and reptiles. Their claws are particularly useful for gouging trees to extract sap and gums, while their incisors assist in peeling away bark. They puncture the tree’s exterior before moving to other trees, only to return later to enjoy the exudate that has gradually seeped out. Typically, only a small amount of sap or gum is released, and the white-headed marmoset spends just a few minutes at each gouged spot. They then continue this process at various trees, which demands an impressive memory from the marmosets.
Behavior and Lifestyle
The white-headed marmoset is a diurnal monkey, meaning they are awake and active during the day and sleep at night. They are active for around 11 hours per day, from sunrise to sunset. They spend their day traveling, eating, and resting. Although, during the wet season they will spend much of their time resting.
They are described as intensely affiliative, meaning they can often be found grooming one another and cuddling during sleep. This affiliative nature lends itself to great cooperation, which has been seen in marmosets mobbing wild cats to deter them from capturing an individual. They are highly arboreal, which is important in avoiding predators in the forest. They vertically leap between trees and cling to the branches. This is a highly effective method of movement that allows the white-headed marmoset to move quickly and efficiently. This method of movement allows them to be precise and deadly hunters. They can pounce on their prey from several meters away.
The white-headed marmoset usually lives in groups of about 10 individuals, although groups of up to 20 have been observed. They are multi-male and multi-female groups. Compared to the vast majority of other primates, marmosets have a unique social order. This social order is different in that there is usually a dominant male and female that leads the group. Dominance is based on age and only the dominant female will reproduce. The rest of the group is composed of adult offspring of the dominant pair and one to two immigrants from outside the group. Adult white-headed marmosets typically leave their natal group in early adulthood. This dispersal from the group helps avoid inbreeding and increases the individual’s chance of becoming part of a dominant pair somewhere else.
Another key feature of white-headed marmoset sociality is the allocare exhibited by all group members. Allocare of infants is essentially care given by an individual who is not the mother. Fathers, sisters, and brothers all participate in caring for newly born members of the group so that the mother may rest and forage. This investment is beneficial for the fathers because it ensures that the dominant female will be able to produce the milk to keep the infants alive, making it more likely that his genetics will be passed on through generations, and beneficial for the brothers and sisters so that they may practice for their own offspring later on.
White-headed marmosets have high-pitched calls that they will use when they feel threatened or are surprised. There are different types of alarm calls that range from short ascending vocalizations, and quick descending calls. High-pitched whistling vocalizations are important in making connections for mates and maintaining existing bonds. Although these vocalizations are important, the most important communication tool for the white-headed marmoset is visual communication. Due to their small size, they have developed silent visual cues that allow them to communicate with one another without alerting predators of their location. Frowning, squinted eyes, mouth open, and wide eyes are just a few of the nonverbal cues these monkeys will give to one another to convey a message.
The white-headed marmoset has what is referred to as a cooperative breeding system. This is a system in which all members of the group contribute to the rearing and well-being of the youngest members of the group. After a pregnancy of about 4 ½ months, the dominant female usually bears twins, which is extraordinarily physically demanding of a small primate. To offset that demand, the dominant male and subordinate males and females help carry the infants, groom them, and sleep with them to ensure their safety. This allows the mother time to rest and forage to be able to maintain her milk supply. It is common for the breeding female to have two births in a year, which requires an immense investment. The dominant female suppresses ovulation in the other females through the release of pheromones. Researchers are not entirely sure of the biological mechanisms behind this. If a non-dominant female happens to give birth to an infant, it is not uncommon for the dominant female to kill them to monopolize care for her own young.
As fruit eaters, the white-headed marmoset is a seed disperser in their environment. Additionally, since they eat insects, they help prevent the predation of leaves and flowers.
The International Union for Conservation of Nature lists the white-headed marmoset as Least Concern (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
Although they are facing many challenges that other primates face, namely habitat loss due to deforestation and fragmentation, the white-headed marmoset seems to adapt well to these challenges. Rural settlements, agricultural expansion, isolation, and habitat reduction are all issues that are slowly encroaching on these monkeys. In Minas Gerais, less than 7% of the original forest remains intact. Luckily, despite this, white-headed marmosets have remained abundant in numbers. Many marmoset species are hunted for the pet trade, but that does not seem to affect white-headed marmosets on an international scale, though, locally they are sometimes pursued and kept as pets.
The white-headed marmoset is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
The white-headed marmoset lives in several protected parks and reserves. The Serra do Cipo National Park, Minas Gerais, Fazenda Córrego de Areia Reserve, Linhares Forest Reserve, Fazenda São Joaquim Reserve, and Sooretama Biological Reserve are among some of them. Though the marmosets appear to have a healthy population, land and water management are still suggested actions, as well as research into their population size, trends, life history, and ecology. Ongoing monitoring is suggested to help keep up with the population so that we may accurately assess the species well being.
- https://www.inaturalist.org/taxa/43372-Callithrix-geoffroyi
- https://stlzoo.org/animals/mammals/lemurs-monkeys-apes/geoffroys-marmoset
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- https://nationalzoo.si.edu/animals/geoffroys-marmoset
- https://resourcelibrary.clemetzoo.com/Animal/136
- https://www.iucnredlist.org/species/3572/191701212
- https://www.marmosetcare.stir.ac.uk/understanding-behaviour/faces.html
- https://primate.wisc.edu
Written by Robyn Scott, November 2024