Download SILVERY MARMOSET Scientific name – Mico argentatus

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