Geographic Distribution and Habitat
The black-tufted marmoset (Callithrix pencillata), sometimes called the black-pencilled marmoset and known as Mico-estrela in Portuguese, inhabits numerous areas throughout Brazil.
Marmosets are typically resilient creatures who have the ability to thrive in many habitats, including busy cities like Rio de Janeiro, where black-tufted marmosets are actually quite common. They are also perfectly happy in lush and healthy primary forests, where they live high up in the treetops just below the canopy, they show a surprising preference for disturbed or secondary growth forests.
Historically, their small size has made black-tufted marmosets popular pets. This trend has allowed the species to be gradually introduced to several places throughout Brazil where they are not native, including its capital city.
Despite their resilience as a species, and though they remain quite common throughout Brazil, black-tufted marmoset populations are currently in decline.
Size, Weight, and Lifespan
Marmosets are notably small species of primates, and the black-tufted variety are no different. Individuals are anywhere from 9–11 in (22–28 cm) in length, not including their long tails that are more than twice as long as their bodies. They can weigh up to 16 ounces (454 g). Males are typically larger than females.
In captivity, marmosets have been known to live up to 15 years. It is not currently clear how long black-tufted marmosets live, on average, in the wild. Lifespans likely vary depending on the type of environment individuals inhabit.
Marmosets are particularly small primates. Their little bodies darts about the branches with striking agility, aided by their forward-facing eyes and long tail. The hands with which they grip and grasp have long nails and—with no opposable thumbs—look more like claws. Their ears are made prominent by the clownish tufts of hair protruding up around them.
Black-tufted marmosets have a dark pelage. As their name suggests, their ear tufts are black. Their faces are either black or dark brown, and often sparse with strands of white hair on their foreheads and around their noses and mouths. Their backside is also black, but their upper torso and limbs are gray. Their long gray tails are ringed all the way to the tip with black ripples.
Black-tufted marmosets are omnivores and primarily eat tree saps and other exudates like gums and resins. Their diet is much more diverse than that, however. Marmosets very happily eat fruits, insects, mollusks (such as snails), and even small vertebrates (such as lizards). Their varied diets are the primary reason why they are such a resilient primate species.
Behavior and Lifestyle
Black-tufted marmosets are arboreal monkeys who almost never descend to the ground. They prefer the comfort of the treetops just below the canopy, where there are fewer predators. As a diurnal (active during daylight hours)—and particularly social—species, groups spend their days traveling to find food, resting, playing, and grooming themselves or each other.
Black-tufted marmoset groups seem to vary their locations as seasons change from wet to dry. Fruits and flowers make up the bulk of their diet during the rainy season, while resins and saps sustain them during the dry season. Black-tufted marmosets forage the exudates from trees using their specialized lower incisors and tiny claw-like hands to nibble and scrape their way through the protective layer of bark.
Groups also engage in scent marking. It is likely that this behavior is used to ward off other primate species (not fellow marmosets), since different groups of marmosets regularly and willingly share space and resources with one another.
Black-tufted marmosets are known as Mico-estrela in Portuguese, which translates to “star tamarin” in English.
They prefer to live in degraded or secondary forests.
A resilient and very adaptable species, they partake of a rich and varied diet.
Black-tufted marmosets engage in scent marking, probably to ward off other primate species, not fellow marmosets.
Marmoset species are highly social, living in family groups of roughly three to fourteen members. Typically, a family group is composed of Mom, Dad, their offspring, and occasional adjacent adult relatives. When they are not busy searching for food, family members play and groom one another. Both parents take responsibility caring for their little ones. Younger members of the family reap the benefits of learning new skills from older siblings, who also help with their upbringing.
There is rarely hostility between different familial groups. In fact, separate groups often look out for each other, keeping their eyes peeled for predators and willingly sharing resources.
Marmosets tend to adhere to a dominance hierarchy, with the mating pair of the group at the top. For the rest, status is typically determined by age, with older individuals wielding more authority than their younger counterparts. Just how these hierarchical roles play out in black-tufted marmoset families specifically is not well studied.
Marmosets are vocal species. Groups use a small repertoire of calls to warn each other of predators; each call is specific to a particular predator. Marmosets then take shelter, depending on the type of predator to which the alarm call refers. For instance, if the predator in question is ground-dwelling, marmosets take shelter in the trees. The ways this plays out for black-tufted marmosets specifically remains to be studied.
Marmoset species show an overwhelming preference for monogamy. Black-tufted mating pairs breed twice per year with pregnancy lasting roughly 150 days (5 months). Twins, which are generally uncommon for primate species to bear, are peculiarly common for marmosets. In fact, marmosets are more likely to have a twin than they are a single newborn.
Both parents invest a great deal of time and energy into raising their offspring, who are born exceptionally small and helpless for primates. After being weaned at eight weeks, other family members begin to help out, teaching the little ones how to search and forage for food on their own.
A black-tufted marmoset, male or female, reaches sexually maturity around 18 months of age, though there is variation. Offspring remain loyal to their troop for some time, and usually become parents considerably later in their lives.
More about the reproductive habits and family dynamics specific to black-tufted marmosets remains to be studied.
Black-tufted marmosets play complex roles in the ecosystems they inhabit. They disperse the seeds of almost every fruit they eat. Yet, for the trees that provide them with the saps and gums they relish, black-tufted marmosets are harmful parasites.
Marmosets are prey to snakes, large birds, and, occasionally, wildcats.
The black-tufted marmoset is classified as Least Concern by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. However, populations throughout Brazil are in decline. While black-tufted marmosets are quite resilient in the face of rampant residential and commercial development, adapting to life in major cities and even showing a preference to living in degraded and secondary forests, these trends will eventually reach a tipping point. Deforestation causes multi-faceted issues for primates everywhere, including ones as adaptable as black-tufted marmosets.
As ecosystems begin to crash around primates, many unexpected things can happen. Since 2016, yellow fever outbreaks have ravaged primate populations throughout Brazil’s Atlantic Forest, including black-tufted marmosets. Researchers believe the outbreaks have been brought on by a perfect storm of peculiar environmental changes. Remarkably high rates of rainfall and warmer-than-usual temperatures may have increased the number of mosquitoes and could have allowed the disease to replicate faster in mosquito hosts. Since humans can carry the virus for longer periods without any symptoms, researchers believe that the increase of human tourism to the outbreak areas may be a factor as well. With ecotourism becoming more popular, it is possible that primates are being exposed to the virus via infected tourists who don’t even realize they are carrying the disease when they travel to these areas.
Conservation issues such as population fragmentation and hybridization—both of which effect black-tufted marmoset populations—add additional layers to this process, and it can take years for their consequences to play out. As forests become more fragmented, troops of black-tufted marmosets are becoming increasingly isolated. Over time, this will cause gene flow between groups to stagnate or even halt altogether. When primates’ gene pools bottleneck in this way, they successively become more vulnerable to diseases (yellow fever, for example), greatly affecting the new generations’ chances of survival.
Hybridization occurs when two genetically distinct groups within a species reproduce. While it occurs naturally and is considered by researchers to play an important role in speciation (the formation of new and distinct species in the course of evolution) and evolution, hybridization becomes a problem for the conservation of species when shrinking and fragmented forests push genetically distinct groups together, increasing the frequency with which they produce hybrid offspring. This can be detrimental to the process of conserving endangered species on multiple fronts. In addition to compromising the unique set of genes that allow for a distinct species to exist, hybrid offspring are potentially less fit than their parents and less likely to produce viable offspring of their own one day. Thus, as different species of marmoset troops are pushed together by human forces, there is the potential that the hybridization resulting from interspecific breeding could endanger all marmoset species, not just the black-tufted variety.
The most popular primate species to keep as pets in the world, marmosets are regularly hunted and sold on the exotic pet trade—an extremely cruel fate for any primate. Infant marmosets—who would have otherwise been nurtured and taught how to survive by their familial group—end up in the care of owners who know nothing about these creatures’ many and unique social, emotional, and physical needs. Even if they did, keeping a marmoset healthy and alive in captivity is a struggle. Confined to poor living conditions, pet marmosets become malnourished, develop severe dental problems, and suffer major health troubles such as metabolic bone diseases, which are brought on by a prolonged lack of sunlight.
The black-tufted marmoset is categorized as Least Concern by the IUCN, so there is little work being done specific to their conservation at this time. Though the species’ numbers are in decline, it remains quite common throughout Brazil. Furthermore, the species’ hardiness and adaptability, as well as its apparent preference for degraded or secondary rainforest, makes its protection less of a priority for conservationists than other, more vulnerable primates. Currently, whether native or introduced, viable groups of black-tufted marmosets reside in more than twenty national parks or other protected areas. Thus, the work being done by conservationists in the names of other primate species is likely to have positive effects for black-tufted marmosets who just so happen to share ranges with them. All that being said, there is still a great deal of research left to be done concerning black-tufted marmosets, and conservation of the species is important to maintaining the ecosystems where they are native.
Where they have been introduced, however, black-tufted marmosets are sometimes known to disrupt ecosystems, complicating survival for native primate species in those areas. The golden lion tamarin is one such example. This endangered species of tamarin monkey is particularly vulnerable to outside competition. As they and black-tufted marmosets rely on similar food sources, the two species are at odds with one another where their ranges have come to overlap. Golden lion tamarins are more adversely affected by Brazil’s growing conservation threats and are therefore severely disadvantaged when forced to compete with hardier and more adaptable black-tufted marmoset invaders.
Written by Zachary Lussier, September 2019