Pygmy marmoset

Life span: 12 years Total population: Unknown Regions: Brazil, Ecuador, Bolivia, Colombia, and Peru Gestation: 4.5 months (142 days) Height: 136 mm (M & F) Weight: 119 g (M & F)

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Diagnosis of two subspecies is fairly recent as is the change in genus from Cebuella to Callithrix, therefore some publications simply refer to one species in the genus Cebuella.

MORPHOLOGY

Pygmy marmosets are the smallest monkeys in the world, weighing a mere 119 g (4.20 oz) on average and measuring, on average, 136 mm (5.35 in) (Soini 1988; Rowe 1996). Males and females are very similar in size, though females are slightly heavier (Soini 1988). There are few distinguishing morphological differences between the subspecies, which may only differ slightly in ventral pelage color (Groves 2001). They have brownish-gold fur with black ticking on their shoulders, backs, and heads, while their ventral fur is light yellow to white. Infants are born with different pelage than is seen in adults; they are a lemon-yellow color with black ticking over their bodies while the head is a dark grey with yellow fur on and around their ears. By the end of the first month, they lose this coat and resemble adults (Soini 1988). Adult pygmy marmosets have tails that are longer than their bodies and marked with conspicuous black rings. The fur on their faces sweeps back over their forehead and ears and they have two white marks on either side of their mouth and a white, vertical line on their noses (Soini 1988). These facial markings probably serve to enhance perception of facial expression and head movements in visual communication in the diffuse light of dense forests (Soini 1988). Though they exhibit squirrel-like patterns of locomotion, including quadrupedally running up and down tree trunks, vertically clinging to tree trunks as they feed on sap, and branch and vine-running on both the top and underside surfaces of horizontal substrates, they are not more closely related to squirrels than other primates (Kinzey 1997). Their small body size allows them to use very slender supports but does not inhibit their locomotion; pygmy marmosets can leap up to five meters (Rowe 1996; Kinzey 1997). They are also able to turn their heads 180 degrees, an adaptation which allows them to scan the environment for predators while vertically clinging to a tree (Kinzey 1997). Pygmy marmosets are able to support their weight on the tips of their long, sharp, claw-like nails (called tegulae) which are different from the flat nails (called ungulae) seen in other primates, including humans, and are probably an adaptation to a life spent clinging to trees (Kinzey 1997; Sussman 2000). An additional characteristic that aids in their exudate-eating behavior is the shape of their lower incisors. They are narrow and elongated such that the five teeth in the front and center of the lower jaw are all the same length. This helps them gnaw into trees efficiently and stimulate sap flow (Sussman 2000). They also have an enlarged cecum, a part of the digestive tract which allows extended time for the breakdown of plant gums (Sussman 2000). Another unusual characteristic seen in pygmy marmosets and other callitrichines is the pattern of giving birth to non-identical twins more frequently than singletons (Soini 1988).

RANGE

CURRENT RANGE MAPS (IUCN REDLIST): Callithrix pygmaea Found in Peru, Ecuador, Colombia, Bolivia, and Brazil, pygmy marmosets range over a large area and the subspecies are isolated by geographic barriers which include several large rivers. The northern subspecies, C. p. pygmaea, is found in the state of Amazonas, Brazil, southern Colombia, northern Bolivia, northeastern Ecuador, and eastern Peru (van Roosmalen 1997; Yépez et al. 2005). Its range is bound by the Rio Solimões and Rio Caquetá. C. p. niveiventris is found in eastern Peru and Amazonas, Brazil south of the Rio Solimões and north of the Rio Purus. It extends as far east as the Rio Madeira and is bound in the west by the Andes (van Roosmalen 1997; Groves 2001). Given their tiny body size and the type of forests in which they are found, wild pygmy marmosets have been poorly studied and there is a lack of detailed behavioral and ecological data (Soini 1982; Heymann &Soini 1999). Many short-term field studies were carried out in the late 1960s and early 1970s, but the first long-term field study of pygmy marmosets occurred in the mid-1970s to 1980s by Pekka Soini. His findings dramatically increased knowledge about pygmy marmoset social behavior and ecology (Kinzey 1997). Additionally, pygmy marmosets have been studied in captivity at the Anthropological Institutes of Zurich University in Switzerland and at the Wisconsin National Primate Research Center, adding to the knowledge of reproductive parameters, development, behavior patterns, and communication (Soini 1988).

HABITAT

Pygmy marmosets occupy mature evergreen forests in and at the edges of periodically inundated river floodplains. They are habitat specialists that prefer areas with no more than two or three meters of standing water for more than three months out of the year and are found in highest densities in river-edge forests (Soini 1988). If they are found in highland areas, it is usually along small, seasonal forest streams that are subjected to frequent, minor flooding (Soini 1988). They utilize vertical strata of the forest from ground level up to 20 m (65.6 ft) and rarely venture into the highest level of the canopy. The understory is composed of reeds, tall grasses, and a few herbaceous plants, vines, shrubs, and saplings. There are also dense thickets formed by bamboo reeds, shrubs, and vines. The tallest trees in this area often have crown heights between 30 and 40 m (98.4 and 131 ft) which support hanging vines and epiphytes (Soini 1982). Data on rainfall and temperature have been reported for a study site in Peru in the Rio Maniti basin where the rainy season lasts from October to May and the dry season lasts from June to September (Soini 1982; Soini 1986). The highest amount of rain falls in March, with levels reaching more than 340 mm (1.12 ft). During the driest part of the year, only about 150 mm (5.9 in) of rain falls per month. Temperatures remain fairly constant throughout the year, hovering around 27° C (80° F) and 80% humidity (Soini 1982). In Ecuador at the Cuyabeno Faunal Production Reserve, average monthly rainfall from March to August exceeds 250 mm (9.84 in) with considerably drier periods during September through February. Average temperatures fluctuate between 22 and 29° C (71 to 84° F) with the rainy season seeing warmer temperatures (de la Torre &Snowdon 2002). Rivers begin to rise in the beginning of the dry season such that between February and June, the floodplain becomes inundated. During this time, there is an abundance of fruits, but as the floodplain dries out during the dry season, fruits also become noticeably scarce (Soini 1986).

ECOLOGY

Characteristics such as elongated, sharp incisors and claw-like nails are adaptations to the very specific diet of the pygmy marmoset — gums and other exudates. They are exudativore –insectivores and spend the majority of their time gouging holes into trees or vines with their sharp lower teeth and then eating the gum, sap, resin, or latex that is exuded (Soini 1988). Holes are generally ten to 20 mm (.787 in) wide, four to 18 mm (.157 to .709 in) deep, and nearly perfectly circular. The “oldest” holes on a tree are closer to the ground and they get “newer” farther up the tree, indicating a pattern of usage (Ramirez et al. 1977). Insects make up the other important part of the diet, and grasshoppers are especially coveted. Pygmy marmosets forage in the crown foliage of trees at about five to 15 m off the ground, looking in vine-tangles and shrubby vegetation for spiders, orthopterans, butterflies, moths, beetles, and ants (Soini 1988). While 60 to 80% of their total feeding time is spent on exudates, they spend between 12 and 16% on insects, and supplement their diet with fruits, buds, flowers, nectars, and very occasionally small lizards (Soini 1988; Yépez et al. 2005). Pygmy marmosets use sleeping sites, or roosts, each night and their day starts shortly after sunrise when all members of the group leave the sleeping site. Sleeping sites are generally made of dense tangles of vines or, on rare occasion, tree holes. Each group has two or three sleeping sites but only use one on a regular basis (Soini 1988; Sussman 2000). In heavy rain or dark, overcast mornings, pygmy marmosets take up to an hour longer to leave the sleeping site. Once it has left the roost, the group travels directly to their primary exudate tree where the marmosets feed for 30 to 90 minutes on gum that has been exuded during the night (Soini 1988). After this feeding bout, there is a shift in activity to more social activities such as huddling, grooming, and playing. After this brief period of rest from foraging, the group begins to focus on insect foraging and exudate foraging until midday when rest and social behavior become the predominant activities. Intense feeding activities begin again in late afternoon until the group travels back to the roost for the night (Ramirez et al. 1977; Soini 1988). The two peaks of exudate feeding occur between 6:00 and 9:00 a.m. and again between 3:00 and 6:00 p.m. (Yépez et al. 2005). Activities are not always coordinated between all group members; some may be foraging for insects while others are feeding on exudates nearby (Soini 1988). A pygmy marmoset group, ranging in size from two to nine individuals, utilizes a primary exudate tree in its home range until the exudate yield declines at which point they gradually move to a new area, if one is available, in the vicinity of the old home range (Ramirez et al. 1977; Soini 1988). Groups of pygmy marmosets exchange home ranges as one group leaves an area and allows an exudate tree to recover, approximately every few months. When an area remains unoccupied long enough for a tree to begin producing gum in large amounts again, it is a potential new home range for a different group (Soini 1988). Densities of pygmy marmosets are quite high in riverine forests and are up to 233 individuals per km² (90.0 per mi²). Removed from a river’s edge, pygmy marmosets are found in densities closer 50 or 60 individuals per km² (19.3 or 23.2 per mi²) (Soini 1988). With such high densities, home ranges for each group are very small, averaging .003 km² (.001 mi²) but less than .005 km² (.002 mi²), and the horizontal day range within these home ranges about 300 m (.186 mi), but they may travel much farther when considering vertical movement within their home range (Soini 1988). Home ranges of neighboring groups do not overlap and there are few, if any, interactions between groups (Soini 1982). Other primates that are found in the habitats occupied by pygmy marmosets include Saguinus fuscicollis (saddleback tamarin), Saguinus mystax (mustached tamarin), Saguinus nigricollis (black-mantle tamarin), Saguinus tripartitus (golden-mantle saddle-back tamarin), Callicebus torquatus (collared titi monkey), Callicebus moloch (dusky titi monkey), Saimiri sciureus (squirrel monkey), and Aotus (owl monkey species) (Soini 1988; Yépez et al. 2005). Saddleback and mustached tamarins sometimes feed from holes gouged by pygmy marmosets and have been seen aggressively chasing the smaller primates from the tree in order to feed. Interactions with other sympatric primates are uneventful (Soini 1988). Exudate holes are also subject to predation by ants, which move in at night when the pygmy marmosets are not feeding and carry away solidified exudate. Excessive predation by ants forces marmosets to abandon a feeding site (Soini 1988). Because of their extremely small body size, pygmy marmosets are subject to predation by raptors, small felids, and climbing snakes. In some cases, they exhibit mobbing behavior in which the entire group flocks to an intruder, loudly vocalizing and attacking the intruder until it retreats; other times, they remain frozen until the threat has passed (Soini 1988; Kinzey 1997).

Content last modified: June 30, 2005

Written by Kristina Cawthon Lang. Reviewed by Stella de la Torre.

Cite this page as: Cawthon Lang KA. 2005 June 30. Primate Factsheets: Pygmy marmoset (Callithrix pygmaea) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/pygmy_marmoset>. Accessed 2020 July 14.