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Microsciurus flaviventerAmazon dwarf squirrel

By Christee Means

Geographic Range

The Amazon dwarf squirrel is found in South America. It ranges from the Amazon Basin of Colombia, Ecuador, Peru, and Brazil, west of the Rios Negro and Madeira, up to 2,000 m in elevation (Emmons, 1997).

Habitat

These squirrels inhabit lowland to dense, fog-shrouded forests, but seem to prefer palm forests (Nowak, 1999). The Amazon dwarf squirrel uses all levels of the forest, from ground level to the canopy (Emmons, 1997). Major activities of this squirrel are confined to heights under 5 meters, using mainly rough, vertical trunks (Youlatos, 1999).

  • Range elevation
    2,000 (high) m
    ft

Physical Description

The total length of the Amazon dwarf squirrel is 250-273mm (Eisenburg and Redford, 1989). The tail is usually shorter than the head and body length; it is relatively slender, tapered toward the tip and frosted with a dirty white color (Nowak, 1999). The upper parts of the Amazon dwarf squirrel are mostly brown, finely grizzled, and reddish to olive in color. The ventrum is thickly haired, deep to pale orange, with brightest coloration on the chest. The ears are short, not protruding above the crown of the head. The fur behind the ears is pale yellow with short hairs not visible above the rim of the ear (Emmons, 1997).

Reproduction

There are no data on the mating system of this animal.

Although data are lacking on the reproduction of this species, it is reasonable to assume that the young, like most squirrels, are altricial. M. alfari, a closely related species, breeds at least from late April to June, and this may also be the case with M. flaviventer. One female M. flaviventer was found to have two embryos (Nowak, 1999).

  • Breeding season
    These squirrels may breed from April to June, as do congeneric animals.

As in all mammals, the female provides parental care by nourishing her young with milk. It is likely that, as in other squirrels, the young are born in a nest of some sort, with their eyes closed. The mother likely cares for the young in the nest until they are able to venture forth on their own.

Lifespan/Longevity

There are no data available on the lifespan of M. flaviventer.

Behavior

Amazon dwarf squirrels are primarily diurnal. Although usually solitary, these squirrels can be seen in pairs especially during the mating season (Emmons, 1997). They primarily use clawed locomotion to travel and feed, associated with large vertical support use. Quadrupedal bounds and vertical leaps are also common. Claw cling, or hanging on rough surfaces, was the dominant feeding posture occuring on vertical supports (Youlatos, 1999). Amazon dwarf squirrels make nests that consist of a ball of leaves lined with fibers (Emmons, 1997). They have a reputation of being rather curious and can be approached within a short distance before they retreat (Nowak, 1999).

Communication and Perception

Food Habits

The Amazon dwarf squirrel forages for arthropods by searching actively over large trunks, vines, and treefalls. They also feed on a substance that is scraped from the bark of trees (Emmons, 1997). They also feed on fruits and nuts of palms (Nowak, 1999).

Predation

In general, small rodents are frequently on the menu for carnivores, birds of prey, and oportunistic carnivorous animals of all sorts. Although there are no specific reports of predation on this species, it is reasonable to assume that they are prey items.

Ecosystem Roles

The roles that M. flaviventer plays are unknown at this time.

Economic Importance for Humans: Positive

The economic importance of these squirrels has not been evaluated.

Economic Importance for Humans: Negative

No negative impact of this species has been reported.

Conservation Status

M. flaviventer currently has no special conservation status. However, because it is an inhabitant of threatened rainforests in the Amazon River basin, this may not always be the case.

Contributors

Christee Means (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor), University of Wisconsin-Stevens Point.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Eisenburg, J., K. Redford. 1989. Mammals of the Neotropics Vol.1. Chicago, IL: University of Chicago Press.

Emmons, L. 1997. Neotropical Rainforest Mammals. Chicago, IL: The University of Chicago Press.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The John Hopkins University Press.

Youlatos, D. 1999. Locomotor and postural behavior of *Sciurus igniventris* and *Microsciurus flaviventer* in eastern Ecuador. Mammalia, 63(4): 405-416.

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