The squirrel-sized Black lion tamarin (otherwise called the Golden-rumped lion tamarin) is closely related to the Golden lion tamarin. Like the latter, this animal possesses considerably long digits, helping it to catch small insects. The squirrel-sized Black lion tamarins are currently among the most endangered mammals around the globe. This species exhibits glossy black fur with reddish-golden patches on its rump, thighs and base of the tail. The face is surrounded by a long, black colored mane.
The original range of this species used to cover central and western parts of the state of São Paulo (Brazil). Currently, the Black lion tamarins occur in two isolated areas: Morro do Diabo State Forest Reserve in southwestern São Paulo, occupying a territory of 375 sq. km.; and the small Caetetus Reserve in central São Paulo, covering 23 sq. km. Preferred types of habitat for these animals are lowland semi-deciduous forest as well as macega forest, usually dominated by small bush-like trees.
As diurnal animals, the Black lion tamarins are active during the daytime hours. They are highly social creatures, forming family units, composed of an adult pair and their offspring from the last 2 - 3 years. The male and the female usually share dominance in these social units, defending their territory from intruders and even fighting them off when necessary. Members of the family groups spend all their time together. Becoming reproductively mature, young males disperse to find mates. Occasionally, numerous groups gather to form large aggregations, where newly matured individuals can find mates. During such gatherings, adult males and females keep distance to avoid conflicts.
The Black lion tamarins are omnivores. The usual diet of these animals primarily consists of insects and fruits, supplemented with small lizards, small vertebrates, small birds as well as eggs of birds (when they are able to catch these types of food).
The Black lion tamarins have a monogamous mating system, where one male mates with one female exclusively. However, populations in some areas exhibit polyandry. When a group contains more than one mature male, the female often mates with multiple males to hide paternity of her offspring. Breeding and births usually occur from spring to autumn. Meanwhile, populations in Brazil mate and breed between August and March. Duration of pregnancy is unknown, although females of other related lion tamarins usually undergo 125 - 132 days of gestation. Females can yield up to 3 - 4 young per litter, although twins are most common. The newborn babies live mainly with their mother until 2 - 3 weeks old, when the father begins to care for them. He will remain with his offspring during most of the day, carrying them to their mother every 2 - 3 hours to feed. Weaning occurs after 2 - 3 months old. However, young lion tamarins continue living with their natal group until 16 - 24 months old, when they are mature.
The Black lion tamarins are primarily threatened by habitat loss: this species has lost more than 90% of its Atlantic forest habitat in Brazil due to factors such as logging, development and cultivation. On the other hand, these animals exhibit a high rate of interbreeding and a very low genetic diversity because of living in isolated populations for a long period of time. Hence, they currently face inbreeding depression, which negatively affects the health of these populations. As a result, some populations are unable to grow, survive and successfully reproduce. Other notable concerns to this species’ population include fires and hunting.
According to the IUCN Red List, the total population of Black lion tamarins is estimated at about 1,000 mature individuals, spread through 11 isolated forests, including 820 animals in the Morro do Diabo State Park, about 40 individuals in the Caetetus Reserve and 114 individuals in remaining 9 localities. Overall, Black lion tamarins’ numbers are decreasing today, and the animals are classified as Endangered (EN) on the IUCN Red List.
Their diet allows Black lion tamarins to act as key seed dispersers of some plant species, thus benefiting the ecosystem of their range.