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SILVERY MARMOSET Scientific name – Mico argentatus Background These tiny monkeys are highly intelligent and well adapted for life in the rainforest. Little is known about the wild status of the silvery marmoset, but it is thought to be in similar trouble to other species of Amazonian primates because of the destruction and fragmentation of its forest habitat for timber and to make way for farmland and housing. Durrell has cared for silvery marmosets in Jersey since 1973, when a captive breeding programme was established to ensure there would be an assurance population should the worst happen in the wild. Species classification The New World monkeys of the family Callitrichidae are found in Central and South America and are commonly known as marmosets and tamarins. These diminutive primates are sub-divided into 6 groups or ‘genera’: Cebuella (pygmy marmosets), Mico and Callithrix (marmosets), Saguinus and Leontopithecus (tamarins) and Callimico (Goeldi’s monkey – an evolutionarily distinct species). Representative species of all these genera, except the pygmy marmosets, are cared for by Durrell in Jersey. The silvery marmoset Mico argentatus is one of 14 species of Amazonian marmoset in the genus Mico. Its scientific name has recently been changed from Callithrix argentata argentata because of the reclassification of many callitrichids, in which many subspecies were given full species status, and Amazonian forest marmosets were separated from Atlantic forest species. The classification or ‘taxonomy’ of the Callitrichidae is constantly changing as a result of new research and the discovery of further species. The callitrichids, with the exception of Goeldi’s monkey, have fewer teeth than the larger New World monkeys - 32 as opposed to 36. The ancestral primate nails on their toes and fingers have evolved into claws on all but their big toes, so that they can climb trees in a squirrel-like fashion and scrabble around in various substrates to catch invertebrate prey. The feature that distinguishes marmosets from tamarins is their lower incisor teeth. Those of marmosets are as large as their canines, which makes it easier for them to gouge holes in tree bark and tap into the nutritious sap that lies beneath. Marmosets depend for a great deal of their food on this ability to use plant exudates. Description The silvery marmoset’s body is covered in silky white-grey hair and it has a long black tail. The eyes are brown, set in a yellowish pink-buff face, which turns darker with exposure to the sun (they get sun tans too!) and may be mottled with black in some individuals. Adults usually weigh 320-350g (11-12oz), with a body length of 2022cm (8in) and tail length of 30-32cm (12in). Males tend to be slightly larger than females and marmosets usually live for 10-15 years in captivity. Distribution and habitat The only place that silveries are found in the wild is a small area of the Amazon basin in northern Brazil, where they live in relatively flat, lowland primary and secondary tropical rainforest. Unfortunately, loggers are reported to have moved into the region increasing the threat to these primates. Feeding habits The silveries normally live in the middle to lower forest canopy and habitually sleep at night in tree holes, dense vegetation and vine tangles. They are active by day and are generally arboreal, but may descend to the ground to cross grassland between areas of forest, and to forage in the leaf litter for animal prey (although this is rare in the wild). Their specialised hands have nimble fingers and strong claws that are used to catch mobile food items. They probe crevices and pull off bark to find tasty morsels and gouge holes in bark to access tree gums and saps, known as ‘exudates’. The diet of the silvery marmoset consists of invertebrates (e.g. insects, spiders), fruit, flowers, gum, small vertebrates (e.g. rodents, birds, frogs, lizards) and sometimes eggs. The proportions of these different food types consumed, and the amount of time devoted to foraging, varies seasonally. For instance, the diet includes the greatest Silvery marmoset species factsheet. © Durrell Wildlife Conservation Trust, July 2006, photograph credit: James Morgan amount of fruit in the wet season and exudates in the dry season, and more time is spent searching for animal prey in the dry season, although the proportion of the diet it represents remains quite constant. Breeding and social behaviour Silvery marmoset social structure and group size is variable, but groups usually consist of an adult male, adult female and several offspring from successive births. Some may have more than one breeding male or female, and also subadults that have joined from other groups. Members of a group stay in close contact in the dense forest by making shrill chirruping calls. Other calls are used in situations of alarm and excitement, and vocalisations are also used to ward off intruders into a group’s home range. Silvery marmosets are highly territorial and adults of both sexes use scent from glands on their chest and genitals to mark out their territories. In captivity breeding can occur at any time of year, but in the wild births are usually between November and March at the onset of the wet season, when food is most readily available. Twins are usually born after a pregnancy of about 140 days, although singletons and triplets also occur. All group members may care for the young soon after birth; this involves food sharing, carrying, grooming and playing. Indeed, the subordinate females in a group are often ‘sexually suppressed’ and prevented from breeding by the dominant female, but gain experience with infants by assisting in babysitting duties. Infants are fully weaned at about 3 months of age and are sexually mature at 15-18 months. Play and mutual grooming are important social aspects of a group’s daily routine and serve to strengthen bonds between its members, as well as to keep fur clean and facilitate infant development. The silvery marmoset has a very distinctive threat display, which is used in confrontations between individuals and includes lowered eyebrows, lipsmacking and rapid tongue flicking. restricted range, it is not hunted, though some animals are taken as pets. However, only one or two field studies have been conducted, so given that its habitat appears to be coming under increasing threat, further research in the wild is urgently needed to assess the risk that the species faces of becoming extinct in the wild. Since 1977 it has been listed under Appendix II of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora), affording the species protection against unregulated international trade. The future Following the recent re-classification of Amazonian marmosets, fieldwork needs to be carried out as soon as possible to determine the conservation status of many species, including the silvery marmoset. Once this has been done, measures can be taken to ensure the survival of these beautiful and fascinating miniature monkeys. June 2006 Conservation status Very little is known about the population level or ‘status’ of this species and there are no biological reserves within the Silvery Marmosets’ range. However, their numbers are inevitably declining, because of the habitat destruction and fragmentation that is occurring throughout the Amazon. The World Conservation Union (IUCN) currently classifies the silvery marmoset as Least Concern, as although it has a relatively Silvery marmoset species factsheet. © Durrell Wildlife Conservation Trust, July 2006, photograph credit: James Morgan