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Microsciurus alfariCentral American dwarf squirrel

By Ashley Combs

Geographic Range

Central American dwarf squirrels, also known as Alfaro's pygmy squirrels (Microsciurus alfari), are native to Colombia, Costa Rica, Nicaragua, and Panama. However, abundance in Nicaragua may be limited, to date; only one specimen has been found there, in 1917. (Allen, 1895; Wilson and Reeder, 2005)

Habitat

Dwarf squirrels (Microsciurus) are found in tropical rainforest regions of Central and South America. None of the members of this genus are endangered, although they are rarely seen because they are shy and lead hidden lives. (Allen, 1895)

Dwarf squirrels show a decided preference for heavy forest, particularly those with vines in the undergrowth. In such places, they can descend to the ground and escape by running across the forest floor or find the nearest tree and climb out of sight. Their small size, dull coloring, and quickness make them difficult to catch. Although they are not abundant, the population numbers within this genus may exceed those of larger squirrels. (Allen, 1895; Loveridge, 1935)

  • Range elevation
    1500 ft. to 5300 ft. km
    to mi
  • Average elevation
    3000-4000 ft. km
    mi

Physical Description

Dwarf squirrels are not as small as their name may suggest. They have a head and body length of 15 centimeters (5.9 in) and a long tail, measuring approximately 12 centimeters (4.7 in). These measurements are similar to those of red and gray squirrels. The majority of their body is dark olivaceous brown. However, their head has a reddish-brown hue. They are fulvous grey below their head and on the underside of their limbs; however, the color can vary from a buff, fulvous grey or a rufous hue. Their skull is highly arched, with pronounced swelling on the frontals at the plane of the postorbital processes. Their brain case is strongly deflected at the posterior end and the rostrum is short and broad. Their upper incisors project forward to, or beyond, the plane of the tip of the nasals, and their jugal is relatively wide. Their inferior margin is abruptly depressed anteriorly where it joins the maxilla. (Allen, 1895; Wilson and Reeder, 2005)

  • Average length
    27 cm
    10.63 in

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 their young, like most squirrels, are altricial. It is also probable that their breeding season is likely in April, May, and June, as in other squirrels. This notion was further supported by the collection of a male specimen whose testes were in breeding condition during the month of June. (Loveridge, 1935; Means, 2003)

  • Breeding season
    Central American dwarf squirrels likely mate during the months of April, May, and June.

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. (Koprowski, et al., 2008; Means, 2003)

Lifespan/Longevity

There is currently no available information about the lifespan of this species.

Behavior

Central American dwarf squirrels are a very shy and solitary species. They are very hard to locate because their small size and dull coloring helps keep them hidden beneath the heavy forest cover. Although they are diurnal, they have been seen on tree branches by hunters at night, this may suggest some nocturnal activities. (Handley, 1966; Loveridge, 1935)

Home Range

There is currently no information available about this species home range.

Communication and Perception

Because Central American dwarf squirrels tend to stay hidden in heavily forested areas, there is currently no information about their forms of communication and perception.

Food Habits

The only Microsciurus alfari stomach contents that have been examined contained material too finely divided to identify. However, it is likely that they eat nuts from the ivory-nut palm groves that they inhabit. They probably have a common granivore diet consisting of seeds, grains, and nuts. (Allen, 1895; Loveridge, 1935)

  • Animal Foods
  • insects
  • Plant Foods
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit

Predation

Small rodents are frequently on the menu for carnivores and birds of prey. Even though there are no specific reports of predation on this species, it is reasonable to assume that they are preyed upon by other animals. (Allen, 1895; Means, 2003)

An anti-predator adaptation that Central American dwarf squirrels possess is their small size and dull coloring; this allows them to blend into heavy forest coverings. (Allen, 1895)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Ectoparasites, such as mites and chiggers, use this species as a host. (Tipton, 1966)

  • Ecosystem Impact
  • disperses seeds
Commensal/Parasitic Species
  • mites (Eutrombicula goeldii) (class Arachnida; phylum Anthropoda)
  • chiggers (Trombicula dunni) (class Arachnida; phylum Anthropoda)

Economic Importance for Humans: Positive

The economic importance of these squirrels has not been evaluated. However, as with all squirrels that have a diet consisting of nuts and seeds, they may act as seed dispersers.

Economic Importance for Humans: Negative

No negative feedback has been reported.

Conservation Status

Central American dwarf squirrels occur in Monteverde National Park, Talamanca National Park, and other protected areas.

Other Comments

The Central American Dwarf Squirrel is also known as Alfaro's Pygmy Squirrel. Evidence suggests that this genus is polyphyletic. The entire radiation of tree squirrels in South America appears to have descended from a single lineage that entered the continent with the establishment of the Panamanian isthmus. The divergence between tree squirrels of Central and those of South America closely corresponds in time to the formation of this land bridge. Before then, there was no evidence of squirrels in South America. (Mercer and Roth, 2003)

Contributors

Ashley Combs (author), University of Pikeville, Mathys Meyer (editor), University of Pikeville, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

Glossary

Neotropical

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

World Map

acoustic

uses sound to communicate

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.

arboreal

Referring to an animal that lives in trees; tree-climbing.

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.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
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

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

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.

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

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.

seasonal breeding

breeding is confined to a particular season

sexual

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

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

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

visual

uses sight to communicate

viviparous

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

References

Allen, J. 1895. Descriptions of New American Mammals. Bulletin - American Museum of Natural History, 7: 333. Accessed September 24, 2011 at http://www.biodiversitylibrary.org/page/26894480#page/363/mode/1up.

Handley, C. 1966. Handley: Checklist of Mammals. Pp. 777 in R Wenzel, V Tipton, eds. Ectoparasites of Panama. Chicago, IL: Field Museum of Natural History. Accessed November 20, 2011 at http://www.biodiversitylibrary.org/page/2652331#page/7/mode/1up.

Koprowski, J., L. Roth, L. Emmons, R. Timm, T. McCarthy. 2008. "Microsciurus alfari" (On-line). IUNC Redlist of Threatened Species. Accessed September 22, 2011 at http://www.iucnredlist.org/apps/redlist/details/13409/0.

Loveridge, A. 1935. Canal Zone Pygmy Squirrels. Bulletin of the Museum of Comparative Zoology, 78: 450. Accessed November 20, 2011 at http://www.biodiversitylibrary.org/page/2794455.

Means, C. 2003. "Microsciurus flaviventer" (On-line). Animal Diversity Web. Accessed October 21, 2011 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Microsciurus_flaviventer.html..

Mercer, J., V. Roth. 2003. The Effects of Cenozoic Global Change on Squirrel Phylogeny. Science Magazine, 299: 1568-1572.

Tipton, V. 1966. Ectoparasites of Panama. Chicago: Field Museum of Natural History. Accessed November 20, 2011 at http://www.biodiversitylibrary.org/name/Microsciurus_alfari#.

Wilson, D., D. Reeder. 2005. Mammal Species of the World: A Taxonomic and Geographic Reference. Baltimore, Maryland: The Johns Hopkins University Press. Accessed October 21, 2011 at http://www.google.com/books?id=JgAMbNSt8ikC&pg=PA757#v=onepage&q&f=false.

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