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Sciurus granatensisred-tailed squirrel

By Casey Harrell

Geographic Range

Red-tailed squirrels are found in Central and South America. Their range includes northern Costa Rica, southern Venezuela, Columbia, Panama, and Ecuador. Sciurus granatensis are also found on the islands of Margarita, Tobago, Trinidad, and Barro Colorado Island. Red-tailed squirrels are found from sea level to 3,000 meters, although in Venezuela 93% of red-tailed squirrels are found below 1,500 m. (Emamdie and Warren, 1993; Heaney and Thorington, Jr., 1978; Nitikman, 1985; Nowak, 1999; Thorington, Jr. and Hoffmann, 2005)

Habitat

Red-tailed squirrels are found in a variety of habitats. They are found in both tropical and seasonal forests, in close proximity to water, and in croplands close to human populations. They are primarily found in seasonal rainforests inhabiting lower forest layers. (Heaney and Thorington, Jr., 1978; Nitikman, 1985)

  • Range elevation
    0 to 3,000 m
    0.00 to ft

Physical Description

Red-tailed squirrels are medium-sized squirrels. Their color varies greatly across the range of the species, especially in different habitats. Their dorsal surface is often dark orange, but can range from dull yellow sprinkled with black to all black. Some varieties of red-tailed squirrels have a median, dorsal stripe. Their ventral color ranges from completely white to bright orange-rust. The well-furred tail is dull yellowish brown and may or may not include a black tip. The ventral tail varies from dark yellowish brown to black with a dark yellow edge. The chin and sides of the throat are dark colored with dark yellow highlights with a yellowish-brown ring surrounding the eyes. The winter coat color may vary slightly from the summer coat. Red-tailed squirrels vary in size throughout their geographic range. Males and females tend to be around the same size, although females tend to be slightly larger on Barro Colorado Island in Panama. Body masses range from 228 to 520 g with body length ranging from 330 to 520 mm. Tail length is 140 to 280 mm. The length of the hind feet is 40 to 65 mm, the length of each ear is 16 to 36 mm, the length of the skull is 42.5 to 68.3 mm, and the width of the cranium is 20.0 to 25.6 mm. Sciurus granatensis has a broad skull that is deep in the orbital region. The cranium is arched, the snout is long, and the bullae are small. (Heaney and Thorington, Jr., 1978; Nitikman, 1985; Nowak, 1999)

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • Range mass
    228 to 520 g
    8.04 to 18.33 oz
  • Range length
    330 to 520 mm
    12.99 to 20.47 in

Reproduction

Red-tailed squirrels generally breed from late December or early January through October. Some red-tailed squirrels may grunt, squeal, and chase each other, but it is not known if that is a mating behavior. During mating season, males begin to search for and follow females three or more days before they come into heat. The day the female comes into heat, many males begin to enter her home range and chase her until mating occurs. The male loses interest within 15 to 30 minutes following mating. (Fleming, 1970; Nitikman, 1985)

The gestation period of red-tailed squirrels is less than two months. Young are born hairless and with closed eyes weighing approximately 9 to 10 g at birth. The litter size is usually 1 or 2 squirrels, although in rare cases litter size may be up to 3. Red-tailed squirrels can have 2 to 3 litters per year. Fur begins to grow on the young approximately 14 days after birth and their eyes open approximately 30 to 32 days after birth. (Heaney and Thorington, Jr., 1978; Koprowskia and Lurzb, 2007; Nitikman, 1985; Nowak, 1999; de Magalhaes and Costa, 2009)

  • Breeding interval
    Red-tailed squirrels have 2 to 3 litters per year.
  • Breeding season
    Red-tailed squirrels breed from late December to late October.
  • Range number of offspring
    1 to 3
  • Average number of offspring
    1.93
  • Range gestation period
    2 (high) months
  • Average weaning age
    61 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Young stay in the nest approximately six weeks after birth. When the mother leaves the nest, she covers her young with nest material. After the period of lactation, which is approximately 61 days, the mother leaves her young. Males have no parental involvement in their young. (Heaney and Thorington, Jr., 1978)

  • Parental Investment
  • altricial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Not much is known about the lifespan of red-tailed squirrels in the wild, but it is estimated that maximum lifespan is between 6 and 7 years. During a study on Barro Colorado Island, an individual that was approximately 1 year old, was captured and marked and re-captured multiple times for 6 years. The maximum lifespan in captivity is approximately 11.5 years. (Heaney and Thorington, Jr., 1978; Nitikman, 1985; de Magalhaes and Costa, 2009)

  • Average lifespan
    Status: wild
    7 years
  • Average lifespan
    Status: captivity
    11.5 years

Behavior

Red-tailed squirrels are usually solitary and are only seen in groups when breeding, feeding, or with their young. Even when they are in groups, red-tailed squirrels usually avoid each other. Adult female red-tailed squirrels are usually not seen within 10 m of other individuals, but they have been documented chasing each other. They avoid one another while feeding and are never found in the same tree at one time. The majority of their day (64%) is spent sitting, while only about 3% is spent grasping, jumping, climbing, or doing other activities. Red-tailed squirrels are generally silent, unless they are alarmed, during which they will let out a few short, hoarse sounds. They also have been known to let out grunts and squeals. Red-tailed squirrels travel 50% of the time on the trunks and large branches close to the center of trees. (Fleming, 1970; Garber and Sussman, 1984; Nitikman, 1985)

Home Range

The average home range area of males is estimated to be 1.5 ha. and the average home range of females is estimated to be 0.65 ha. On a study done in Panama, home range for males was 0.83 ha to 2.15 ha. Females home ranges were 0.39 ha to 0.86 ha. Male home ranges overlap greatly with one another and overlap with home ranges of females. Female home ranges do not usually overlap. (Heaney and Thorington, Jr., 1978; Nitikman, 1985; Nowak, 1999)

Communication and Perception

Normally Sciurus granatensis are quiet and solitary, but they often let out grunts and squeals and chase each other. This may or may not a mating behavior. Like other squirrels, they use body postures and gestures to communicate and have a keen sense of smell used to find food and determine sexual receptivity. (Fleming, 1970)

Food Habits

Approximately 65% of the diet of red-tailed squirrels is made up of fruits, nuts, and seeds with the majority of their diet coming from Scheelea zonensis, Dipteryx panamensis, Maripa panamensis, and Gustavia superba. Although they feed mainly on large fruits and seeds, their diet may include leaves, bark, mushrooms, and flowers. A study done on Barro Colorado Island found that 73% of total feeding observations were on four species of fruit; Dipteryx panamensis, Astrocaryum standleyum, Scheelea zonensis, and Gustavia superba. When available, acorns and hickory nuts are greatly preferred. Red-tailed squirrels have been documented feeding on small insects. In areas where humans reside, red-tailed squirrels feed on cultivars, mangos, avocados, maize, coconuts, and bananas causing damage to these crops. In central Panama, red-tailed squirrels prefer feeding on hard-shelled nuts over softer-shelled nuts. Red-tailed squirrels mainly search for food on the ground, but will usually climb up into the trees before eating food they have found. They also look for food in the crowns of trees over 30 m above the ground. (Garber and Sussman, 1984; Glanz, 1984; Heaney and Thorington, Jr., 1978; Nitikman, 1985; Nowak, 1999)

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers
  • Other Foods
  • fungus

Predation

Humans occasionally prey on red-tailed squirrels, both for food and to reduce their impact on crops, such as mangos, avocados, corn, coconuts, and bananas. Natural predators include capuchin monkeys (Cebus capucinus) and boa constrictors (Boa constrictor). They may also be preyed on by raptors, felids, and arboreal snakes. (Nitikman, 1985; Wright, et al., 2000)

Ecosystem Roles

Red-tailed squirrels disperse the seeds of the fruits that they feed on and serve as prey for predators. They may contribute to the dispersal of fungal spores as well. (Steven and Putz, 1984)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Red-tailed squirrels disperse seeds of the plants they feed on. Sciurus granatensis are hunted for food by humans. (Nitikman, 1985; Wright, et al., 2000)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

In areas of human population, red-tailed squirrels feed on crops such as mangos, avocados, maize, coconuts, and bananas, causing crop damage. (Nitikman, 1985)

  • Negative Impacts
  • crop pest

Conservation Status

Red-tailed squirrels have a stable population standing. They are neither endangered nor close to extinction even though they are hunted by humans.

Other Comments

Sciurus granatensis, along with many other species of Sciurus swim by dog paddling. (Nowak, 1999)

Contributors

Casey Harrell (author), Radford University, Joel Hagen (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

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

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

food

A substance that provides both nutrients and energy to a living thing.

forest

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

frugivore

an animal that mainly eats fruit

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.

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

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

sedentary

remains in the same area

sexual

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

solitary

lives alone

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

Emamdie, D., J. Warren. 1993. Varietal Taste Preference for Cacao Theobroma cacao L. by the Neotropical Red Squirrel Sciurus granatensis (Humboldt). Biotropica, 25: 365.

Fleming, T. 1970. Notes on the Rodent Faunas of Two Panamanian Forests. Journal of Mammalogy, 51(3): 475.

Garber, P., R. Sussman. 1984. Ecological Distinctions Between Sympatric Species of Saguinus and Sciurus. American Journal of Physical Anthropology, 65: 135-146.

Glanz, W. 1984. Food and Habitat use by two Sympatric Sciurus Species in Central Panama. Journal of Mammalogy, 65(2): 342-347.

Heaney, L., R. Thorington, Jr.. 1978. Ecology of Neotropical Red-Tailed Squirrels, Sciurus granatensis, in the Panama Canal Zone. Journal of Mammalogy, 59(4): 846-851.

Koprowskia, J., P. Lurzb. 2007. Tree Squirrel Introduction: A Theoretical Approach with Population Viability Analysis. Journal of Mammalogy, 88(5): 1271-1279.

Nitikman, L. 1985. Sciurus granatensis. Mammalian Species, 246: 1-8.

Nowak, R. 1999. Order Rodentia. Pp. 1265-1268 in Walker's Mammals of the World, Vol. 2, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

Steven, D., F. Putz. 1984. Impact of Mammals on Early Recruitment of a Tropical Canopy Tree, Dipteryx panamensis, in Panama. Oikos, 43(2): 207-216.

Thorington, Jr., R., R. Hoffmann. 2005. Family Sciuridae. Pp. 761 in D Wilson, D Reeder, eds. Mammal Species of the World, Vol. 2, Third Edition. Baltimore, Maryland: The Johns Hopkins University Press.

Wright, S., R. Ibáñez, M. Moreno, M. Gallardo, I. Dominguex, H. Zeballos. 2000. Poachers Alter Mammal Abundance, Seed Dispersal, and Seed Predation in a Neotropical Forest. Conservation Biology, 14(1): 227-239.

de Magalhaes, J., J. Costa. 2009. A database of vertebrate longevity records and their relation to other life-history traits. Journal of Evolutionary Biology, 22(8): 1770-1774.

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