Geographic Distribution and Habitat
The buffy-tufted-ear marmoset (Callithrix aurita), also called the white-eared marmoset, is endemic to the states of Minas Gerais and Rio de Janeiro of southeastern Brazil, within their montane rainforests of the inland plateau, at chilly dry-season altitudes of up to 4,265 feet (1,300 m). Multiple studies from 1982 to 1998 were carried out to better understand their geographic range. Recent studies indicate that most buffy-tufted-ear marmoset populations inhabit these montane forests, with a few outlying populations in the foothills or lowland coastal forests.
Buffy-tufted-ear marmosets (C. aurita) and buffy-headed marmosets (C. flaviceps) have interbred, creating a hybrid species that is recorded as living in Carangola in the Serra do Brigadeiro, Minas Gerais. This hybridization is challenging the viability of already endangered pure C. aurita populations.
Size, Weight, and Lifespan
Buffy-tufted-ear marmosets are small primates with a body mass of about 11 oz (306 g). Though little is known about the length of this marmoset species specifically, similar marmoset species average 5.5–7.5 in (14–19 cm), excluding the tail.
Common marmosets have a lifespan of 12 years, so we can conclude that buffy-tufted-ear marmosets likely have a similar lifespan.
Marmosets in general are distinguished by their small size, modified claws (rather than nails), and two molar teeth. They lack a prehensile tail.
Buffy-tufted-ear marmosets have smaller incisors than other Callithix species because they do not use them to perforate bark. They have furry faces and a dusty black pelage that covers their entire body. They have short snouts with flat noses, round yellow eyes, and a down-turned mouth that suggests eternal dissatisfaction. A blaze of reddish-orange hair covers the top of their head, while long white tufts extend out of their ears (hence their “buffy-tufted-ear” moniker). They have long fingers—with claws instead of nails, as noted above—that are covered with dusty yellowish-orange fur.
Unlike most marmosets, buffy-tufted-ear marmosets are primarily insectivorous, although their diet is generally omnivorous. Ants, termites, larvae, caterpillars, insect galls, and large-winged insects are all favorites of buffy-tufted-ear marmosets. They supplement their diet with flowering plants, gums, cacti, nectar, frogs, snails, lizards, and spiders. This diet provides sufficient protein for their small bodies.
Unlike other marmosets, buffy-tufted-ear marmosets do not gouge tree bark for gums and sap. Most marmosets possess dental adaptations that allow them to gouge tree trunks and branches, using their sharp incisors to stimulate the flow of gum. Buffy-tufted-ear marmosets do not use their incisors to obtain plant exudates, hence the evolution of their short muzzles. Instead, when they feed on plant exudates like gum, they seek out sites where it is available without requiring gouging.
Behavior and Lifestyle
Buffy-tufted-ear marmosets are diurnal (active in daylight hours) and arboreal, spending most of their lives in trees. Their small size and distinct coloration make them difficult to detect and observe, so their behavior is little-studied.
Some details about their behavior and lifestyle can be gleaned from other species in the Callithrix genus. For instance, common marmosets remain within their home range while traversing the forest canopy based upon availability of plant exudates. Thus, it is likely that buffy-tufted-ear marmosets’ home ranges are also based on food availability.
Common marmosets wake thirty minutes after sunrise and feed intensively for an hour; the rest of the day is spent feeding, socializing, and resting. Then, an hour before sunset, they return to their sleeping sites and sleep together as a group, which affords greater protection against predators (strength in numbers). Buffy-tufted-eared marmoset behavior is likely similar.
The buffy-tufted-ear marmoset belongs to the class of New World monkeys, also called Platyrrhines. Fossil evidence indicates that monkeys first appeared in the New World approximately 30 million years ago during the Oligocene Epoch.
Buffy-tufted-ear marmosets live in fluid groups of between four and 15 individuals. Group composition may include multi-male/multi-female, one male/multi-female, or one female/multi-male groups.
Little else is known about their group dynamics; however, we do know that common marmoset groups can include up to three family generations. Females within a group are usually closely related (mothers, daughters, and/or sisters). Common marmoset groups retain their adolescent members until they reach adulthood, at which point males emigrate to other groups.
The dominance hierarchy in marmoset species is linked to breeding status. Typically a breeding pair dominates the family and maintains its status through aggressive defense. When there is more than one breeding female in the group, one will be dominant over the other. For non-breeding group members, social status is determined by age.
There is little known specifically about the communication habits of buffy-tufted-ear marmosets, but there are commonalities among all marmosets, including how they use vocalizations, visual cues, and olfactory signals.
For long-range vocalizations, common marmosets emit alarm calls, which are repeated staccatos or “tsiks” (short calls) to warn other group members. They emit trill calls, which are low-pitched calls, to keep track of other group members. Phee calls, which are high-pitched whistles, are used for group cohesion, defense, and attracting a mate.
For close-range visual cues, a partial open-mouth stare indicates alarm, a frown indicates aggression, a slit stare indicates submission, and ear-flattening indicates submission, fear, or curiosity.
Olfactory signals include secretions from a scent gland on the chest to mark territory and signify social or reproductive status. Marmosets have a specialized organ in their nasal cavity that effectively processes chemical markings left by other animals.
Typically, only one female in the group breeds during a particular breeding season. The singular breeding pair is usually the highest ranking male and female. The breeding female emits chemical cues that, along with her dominant behavior, suppress the hormones of less dominant females in the group. Since they typically give birth to twins, suppressed reproduction in the other related females focuses a great deal of attention and care onto the twins as everyone participates in raising the youngsters. This increases their chances to survive infancy.
The twins are non-identical and are born during the spring after a gestation period of approximately 170 days (almost 6 months). Infants are weaned at 3 months of age. Marmoset females are generally sexually mature at approximately 1.5 years of age while males achieve sexual maturity at just over one year of age.
There is little recorded about the ecological role of buffy-tufted-ear marmosets. More observation and research need to be conducted in order to properly chronicle the buffy-tufted-ear marmoset’s role in its ecosystem; however, it can be assumed that, as insectivores, they play a role in pest control. Their broad omnivorous diet probably also plays a role in reforestation as they drop seeds and pollen as they travel.
The International Union for Conservation of Nature’s Red List of Threatened Species lists the buffy-tufted-ear marmoset as Endangered (IUCN, 2015). Other sources describe the species as “on the brink of extinction in the wild” (World Land Trust, 2015). The Brazilian Red List of Fauna also classifies the buffy-tufted-ear marmoset as Endangered. Additionally, the species is listed in the 2018-2020 “Primates in Peril: The World’s 25 Most Endangered Primates.” The population is estimated at 10,000-11,000 mature individuals, with those number continuing to decline rapidly.
Threats against the buffy-tufted-ear marmoset consist of habitat fragmentation and competition, hybridization, yellow fever outbreaks, human hunting, and widespread destruction of the forests within its range—only 7% of its original range remains.
From 2016 to 2017, a yellow fever outbreak in the buffy-tufted-ear marmoset’s range resulted in 257 confirmed yellow fever cases in the species, though the actual number is likely much higher due to the difficulty of locating tiny marmoset cadavers in the dense forests; across Brazil, the virus impacted more than 7,000 nonhuman primates.
Interbreeding with the buffy-headed marmoset (C. flaviceps) is a considerable threat to the buffy-tufted-ear marmoset, as it could eliminate the remaining wild population as the genetically pure individuals will die out. The common marmoset and black-tufted marmosets, introduced through the illegal pet trade, are also rapidly expanding into the range of the buffy-tufted-ear marmoset, stretching availability of natural resources, like space and food.
The buffy-tufted-ear marmoset inhabits several protected national parks, like Serra da Bocaina National Park, Serra dos Orgaos National Park, Itatiaia National Park, and several other state parks and ecological stations, but a full-scale survey needs to be conducted in order to determine exactly where these marmosets occur in protected areas and how conservation efforts can be improved.
The Mountain Marmosets Conservation Program (MMCP) was established in 2014 after concern was expressed about the threats faced by buffy-tufted-ear marmosets. In 2015, MMCP identified regions with pure populations, hybrid groups, and invasive species and discovered that in approximately 100 different locations, 85 groups of buffy-tufted-ear marmosets and 47 groups of invasive species or hybrids were found. The results of this field survey helped MMCP recognize the urgency of reinvigorating the captive populations of buffy-tufted-ear marmosets. They conducted a plan in 2017 to increase the population size and maintain healthy reproductive pairings. The plan requires more institutions to join in order to reach the population target number of 350–400 individuals (there are at least 5 institutions currently joined now).
In order to combat the increasing population of invasive Callithrix species, the Environmental Secretary of Sao Paulo proposed reproductive restrictions for captive populations of those non-native species in order to reduce a potential surplus and resultant undue release. In 2018, The National Action Plan for the Atlantic Forest Primates and the Maned Sloth (ICMBIO, 2018) included buffy-tufted-ear marmosets along with 12 other primates. The Rodrigo Salles de Carvalho of Rio de Janeiro University has also created an action plan for the buffy-tufted-ear marmoset in order to ensure its survival.
Buffy-tufted-ear marmoset conservation will depend on multiple different actions including:
- Surveying to understand how they are affected by things like invasive species and disease
- Development of effective techniques and protocols to control invasive Callithrix populations
- Monitoring and management with individual movements facilitated by human intervention
- Continued legal protection of the species and its habitat
- Involvement of more institutions
- Promotion & social awareness of buffy-tufted-ear marmoset conservation
Throughout all these conservation plans and initiatives, one thing remains clear: effective and collaborative action needs to be taken soon before this species veers toward the wrong end of the endangered species list.
Written by Rachel Heim, November 2019