Perception Channels: tactile ; chemical
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.
CITES: no special status
IUCN Red List of Threatened Species: data deficient
No negative impact of this species has been reported.
The economic importance of these squirrels has not been evaluated.
The roles that M. flaviventer plays are unknown at this time.
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).
Primary Diet: carnivore (Insectivore )
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).
Biogeographic Regions: neotropical (Native )
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.
Habitat Regions: tropical
Terrestrial Biomes: rainforest
There are no data available on the lifespan of M. flaviventer.
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).
Other Physical Features: endothermic ; bilateral symmetry
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.
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.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
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.
Parental Investment: altricial ; female parental care
The Amazon dwarf squirrel (Microsciurus flaviventer) is a chipmunk-sized tree squirrel native to South America.
As its name suggests, the Amazon dwarf squirrel is relatively small, with a head-body length of 12 to 16 cm (4.7 to 6.3 in) and a tail 8 to 16 cm (3.1 to 6.3 in) long. Adults weigh between 86 and 132 g (3.0 and 4.7 oz), with males being slightly larger than females.[2] The fur varies from reddish to dull brown, fading gradually to yellow or greyish on the underparts. There is a distinctive patch of pale yellow fur behind the ears, while the tail has faint yellowish bands and white frosting.[3]
The limbs are unusually long for tree squirrels. In the forelimbs, the humerus and radius are of equal length, an adaptation thought to increase the squirrel's ability to climb large trees, compensating for a lack of shoulder mobility. The longer hindlimbs allow for stronger muscles, so that the squirrel can leap over larger gaps, relative to its size, than more typically sized squirrels can.[3]
The squirrels are found in the upper Amazon Basin, broadly west of the Purus and Rio Negro rivers, in Brazil, Bolivia, Peru, Ecuador, and Colombia. They typically inhabit evergreen tropical rainforests at up to 2,000 m (6,600 ft) elevation,[3] although they may sometimes be found in more disturbed habitats.[4]
Eight subspecies of Amazon dwarf squirrel are currently recognised:[5][3]
Microsciurus flaviventer taxonomy Subspecies Authority Synonyms Distribution M. f. flaviventer Gray (1867) manarius Western Brazil, northeastern Peru M. f. napi Thomas (1900) avunculus, florenciae Northeastern Ecuador M. f. otinus Thomas (1901) none Western Colombia M. f. peruanus J. A. Allen (1897) none Northern Peru M. f. rubrirostris J. A. Allen (1914) rubicollis Southern Peru M. f. sabanillae Anthony (1922) none Southern Ecuador M. f. similis Nelson (1899) none Far western Colombia M. f. simonsi Thomas (1900) none Central eastern EcuadorThe squirrels use all levels of the forest, from the ground to the tree canopy, but are most commonly found in the understory. They feed on arthropods, tree bark, and fungi, and have been observed to closely follow flocks of birds while foraging, although the reason for this is unclear. They are diurnal and highly arboreal, even for tree squirrels, frequently jumping from branch to branch. They spend the night in nests formed from plant fibres, and located several metres above the ground.[3]
They are mostly solitary, but may be found with others feeding on the same tree. Their calls include a bird-like "trill" and a series of soft "chucks" used as an alarm call. Very little is known of their reproduction, although litters are thought to be small.[3]
The Amazon dwarf squirrel (Microsciurus flaviventer) is a chipmunk-sized tree squirrel native to South America.
