The golden lion tamarin (Leontopithecus rosalia; ), less commonly known as the golden lion marmoset, is a small New World monkey of the family Callitrichidae. Endemic to the Atlantic coastal forests of Brazil, the golden lion tamarin is an endangered species. Its geographic range is entirely within the state of Rio de Janeiro. A 2022/2023 census estimated about 4,800 individuals living in the current primary area of occurrence in the non-coastal area of the São João and Macaé river basins, with unknown but smaller additional numbers in limited coastal forests and to the west of the primary area of occurrence. There is a captive population maintaining about 490 individuals among 150 zoos.
Physical characteristics
The golden lion tamarin gets its name from its bright reddish-orange pelage and the extra-long hairs around the face and ears, which give it a distinctive mane. Its face is dark and hairless. The bright orange fur of this species does not contain carotenoids, which commonly produce bright orange colors in nature. The golden lion tamarin is the largest of the callitrichid monkeys. It is typically around and weighs around . Almost no size difference exists between males and females. As with all callitrichids, the golden lion tamarin has claw-like nails, instead of the flat nails found in other monkeys and apes, although callitrichids do have a flat nail on the big toe.
Golden lion tamarins walk, run, and bound quadrupedally on top of branches, or, less frequently, they run and walk on the ground. When golden lion tamarins run or bound, their hindlimbs alternately overstride their forelimbs, and their feet are set atop the support and grasp it almost perpendicular to the line of travel, making the body's angle of travel oblique rather than precisely parallel to the substrate, a pattern known as "transaxial bounding". In addition, facilitated by their claw-like nails, golden lion tamarins cling and climb on vertical tree trunks (see photographs in Serra (2019), pp 108–117, 137, 155).
Habitat and distribution The golden lion tamarin has a limited current area of occupancy, as most of the original habitat in the Brazilian state of Rio de Janeiro has been lost to deforestation. Today, the species is confined to fragments of forest within the state, including Poço das Antas Biological Reserve, União Biological Reserve, other protected areas, and privately owned lands. Most of the area of occupancy is characterized by vegetation types classified as dense broadleaf evergreen or seasonal deciduous and semideciduous forest, with some tamarins living in areas closest to the coast found in a sandy soil forest type called "arboreal restinga".Kierulff, M.C.M (2000) Ecology and behaviour of translocated groups of golden lion tamarins (Leontopithecus rosalia). PhD thesis, University of Cambridge. pp 41 Golden lion tamarins are thought to occur primarily in low-elevation forests, up to 150 or 300 meters above sea level, but a 1990–1992 survey identified two groups above 500 meters, and reports from the recently identified western geographic area include records above 700 meters.Nascimento, J. L.; Eckhardt, B. L.; Antunes, E. P.; Andrade, F. P. S.; Cronemberger, C.; Soares, R.; Souza, N. F.; Souza, C. S. F.; Ribeiro, E. A.; Pereira, J.; Mattos, E.; Silva, V. M.; Stump, L.; Rubião, E. C. N.; Dias, P. R.; Gomes, M. M.; Silva, C. A. M.; Moreira, S. B.; Pissinatti, A.; Oliveira, L. C. (2019). Novos registros, ampliação da distribuição altitudinal e conservação de Leontopithecus rosalia (Linnaeus, 1766) no oeste do Mosaico Central Fluminense [New records, expansion of altitudinal distribution and conservation of Leontopithecus rosalia (Linnaeus, 1766) in the west of the Central Fluminense Mosaic]. Abstract from the 2019 Brazilian Primatological Conference (in Portuguese).
Golden lion tamarin population estimates in the 1960s and 1970s ranged from only 100 to 600, although these estimates were not based on range-wide censuses. The first such census, carried out 1990–1992, counted about 560 wild individuals and there were about 100 additional individuals from the reintroduction program living in the wild. Since then, following conservation efforts including reintroduction of zoo-born animals and translocation of wild individuals from small, at-risk forest fragments (both largely to areas then unoccupied by tamarins), reforestation with a particular focus on connecting separated areas of habitat, and community-based conservation and engagement programs, the population has grown significantly. Most recently, a 2022-23 census estimated about 4,800 golden lion tamarins living in the current primary area of occurrence in the noncoastal area of the São João and Macaé River basins, with unknown but smaller additional numbers in limited coastal forests and to the west of the primary area of occurrence.
Behaviour and ecology
Diet In the wild, golden lion tamarins eat mostly fruits and small animal prey, in addition to smaller quantities of nectar and plant exudates (tree gum).
Plant material Fruits, mostly ripe, are the plant part consumed by golden lion tamarins for more than 80% of plant species eaten. Tamarins swallow the seeds of most fruits they consume and are considered to function as effective seed dispersers for many plant species.
Wild golden lion tamarins eat from a wide variety of plant species, with 160 species noted in one multiple-group study. Despite this variety of food plants, they appear to get most of their plant food from a smaller subset of species. For example, just seven of the 160 plant species noted eaten by golden lion tamarins in the União Biological Reserve accounted for 56% of total plant feeding observations.
The most common reported source of nectar in golden lion tamarin diets are the flowers of the tree Symphonia globulifera. Nectar consumption typically represents a small proportion of the plant diet (6%-10% of observations or time), but some groups may concentrate heavily on nectar during the cool, dry season in at least some years.
Exudates or tree gum are soft, semiliquid substances produced by trees and lianas in response to damage to exterior bark or to disease. Golden lion tamarins in the Poço das Antas Reserve fed occasionally on tree gum that they found opportunistically on trees and woody lianas, and gum consumption represented less than 2% of total feeding observations or time. Lion tamarins (and other tamarins) lack the dentition and other specializations for gum-feeding characteristic of marmoset genera, e.g., Callithrix and Cebuella.
Animal prey Animal prey reported as eaten by wild golden lion tamarins in at least one study include frogs and tree frogs, amphibian egg masses, lizards, snakes, nestling birds, bird eggs, snails, spiders, centipedes, katydids, grasshoppers, crickets, beetles and beetle larvae, cockroaches, ants, stick insects, butterflies, caterpillars, and insect-infested tree galls. Orthopteran insects (e.g., grasshoppers, katydids, and crickets) were the most commonly eaten prey in one study.
Golden lion tamarins capture most of their prey animals from hidden crevices in tree bark, rotten wood, holes in trees, vine tangles, within curled dead leaves, between the leaves and in the basins of bromeliads, inside hollow bamboo, under the sheaths of palm leaves, or in leaf litter on the ground and debris accumulated in limb junctions and palm apices. A golden lion tamarin captures such hidden prey by inserting its fingers, hand, and even forearm into the visually inaccessible recesses, groping blindly by sense of touch, grasping an encountered prey item, and withdrawing and eating it. This is a form of the foraging technique known as "extractive foraging on embedded foods", and in golden lion tamarins has been termed "micro-manipulation".Bronikowski, E. J., Beck, B. B., and Power, M.L.. (1989) Innovation, exhibition and conservation: Free-ranging tamarins at the National Zoological Park. Proceedings of the 1989 American Association of Zoological Parks and Aquariums Conference: 540-546 Peres reported that such extractive foraging accounted for 98% of prey captures observed in one study in the Poço das Antas Biological Reserve. Lion tamarins (the genus Leontopithecus as a whole) have significantly longer and narrower hands (including longer fingers) than other callitrichids. This is considered to be an adaptation to their micro-manipulation foraging behavior.
Home range and use of space Golden lion tamarin groups are highly territorial; they have areas of exclusive use, but engage in aggressive encounters with neighboring groups at borders and in areas of overlap. These encounters feature chases and characteristic vocalizations and posturing, and can include brief physical contact and fights. Peres proposed that these encounters served to reinforce boundaries and preserve areas of exclusive use, "preventing neighbors from trespassing farther" (p 232). The term "home range" is used here, representing the full area that a tamarin group uses, including both areas of exclusive use and areas of overlap with neighboring groups. For one study group in Poço das Antas Biological Reserve, about 60% of the study group's home range was overlapped by the home ranges of neighboring groups.
A long-term study in Poço das Antas Biological Reserve calculated a mean home range size of 50.5 ha (124.8 acres) for golden lion tamarin groups over one-year periodsHankerson, S. J. (2008) Resource and space use in the wild golden lion tamarin, Leontopithecus rosalia. PhD thesis, University of Maryland. http://hdl.handle.net/1903/8812(pp 66–67), with a range of 17.4-87.7 ha (43.0-216.7 acres). Reports from União Biological Reserve indicate larger home range sizes there, which may be a result of lower population density in União at the time of the studies as well as differences in calculation methods. Golden lion tamarin home ranges are not static over time. One study found a mean of 77% home range overlap for a group between one year and the next. Wild golden lion tamarins use their home ranges unevenly, with some areas used much more heavily than others. In a study in Poço das Antas Biological Reserve, "core areas", where 50% of a group's location records were documented, averaged around 10% of a group's total home range.
Reports of average daily travel distances for individual groups range from 1,339 to 2,135 m (4,393 to 7,005 ft). Single-day travel distances for groups vary more widely. For example, in one study of two groups in União Biological Reserve, single-day travel distances ranged from 401 to 3,916 m (1,316 to 12,848 ft).
Sleeping sites Golden lion tamarins usually spend more than half their time in overnight sleeping sites and thus they are active for less than half the day. Two groups in the União Biological Reserve spent an average of 14.2 hours and 13.1 hours in their sleeping sites (calculated from Table 1). Active periods are longer in the austral summer, which have more hours of daylight. In the Poço das Antas Biological Reserve, golden lion tamarins left their sleeping sites in the morning an average of 10 min after sunrise and entered at the end of the day an average of 82 min before sunset.