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Epixerus ebiiwestern palm squirrel

By Kelsie Carlson

Geographic Range

The western palm squirrel, Epixerus ebii, is native to the western parts of Africa, and has a disjunct range. It is found in coastal forests from Sierra Leone east to Ghana, also from central Cameroon south through Equatorial Guinea and Gabon, and with a third population in the Republic of the Congo.

The range overlaps that of its close relative, the African giant squirrel, Protoxerus stangeri. (Grubb, 2008; Lidicker, 1989)

Habitat

Western palm squirrels occur are found in lowland forests and rainforests, up to 1020 meters. They spend most of their time in the undergrowth of these rain forests. They are mostly seen on the ground and seldom climb higher than their nests, which are on average around 8.1 meters above the forest floor. This species is most often found in mature and old secondary forest, they avoid plantations or flooded forests with high water. (Emmons, 1980; Kingdon, et al., 2013)

  • Range elevation
    1020 (high) m
    3346.46 (high) ft

Physical Description

Western palm squirrels are one of the largest species of squirrels found in African rainforests. They have an average mass of around 592 g (range = 540 to 650 g). Their average head and body length is 284 mm (range = 250 to 310 mm). Their backs are a grizzled grey color, while their undersides range from a warm orange to a red color. The most identifying characteristic of this species is its tail, as it is black-fringed with black-and-white marks above. The underside of the tail has fine longitudinal stripes that fade into an orange brush.

These squirrels are commonly mistaken for their closest relative, Protoxerus stangeri. The species can only be distinguished morphologically by minute differences in their skulls. (Emmons, 1980; Kingdon, 2015)

  • Sexual Dimorphism
  • male larger
  • Range mass
    540 to 650 g
    19.03 to 22.91 oz
  • Average mass
    592 g
    20.86 oz
  • Range length
    250 to 310 mm
    9.84 to 12.20 in
  • Average length
    284 mm
    11.18 in

Reproduction

Not much is known about the mating systems in Epixerus ebii. In one observation, several males were seen chasing after a female in heat. It is thought that the tail and its respective pattern may have an impact on mate selection, but it is unknown how. (Emmons, 1979; Hayssen, et al., 1993; Kingdon, 2015)

Little is known about the reproduction in Epixerus ebii but it has been observed that the litter size is two.

The closely related species Protoxerus strangeri breeds from April to July, with the breeding season lasting around one month. Females of this species may breed twice per season, allowing them to raise two different groups of young simultaneously. Protoxerus strangeri inhabit the same geographic region, but are more arboreal. (Emmons, 1978; Gouat and Yahyaoui, 2001; Waterman, 1998)

  • Average number of offspring
    2

As suggested above, little is known about the reproduction in Epixerus ebii. Young of the closely related species Protoxerus strangeri are seen with their mothers for the first month of their lives. The mothers of this species lactate and protect their offspring, but the young are precocial. (Gouat and Yahyaoui, 2001; Kingdon, 2015)

Lifespan/Longevity

Little is known about the lifespan or longevity in the western palm squirrel. They are relatively difficult to capture, and none are currently in captivity. (Kingdon, 2015)

Behavior

Western palm squirrels are not social squirrels, as they are observed alone around 80% of the time. The rest of the time, they are seen with one to three other squirrels. They usually have very large home-ranges, averaging around 21 hectares. They are considered to be active and quick. On average, males can travel 115 meters in one hour while females can travel 144 meters in that time.

They usually create a nest in a tree, which becomes their parent tree. Their home-range extends out from around that point. Little is known about these nests or dens, other then that they are on average 8.1 meters off of the ground, but can range from 1.5 meters to 20 meters. Unless they are climbing to or from their dens, they spend no time climbing trees.

Western palm squirrels are diurnal, but they have relatively short activity periods. They typically leave their nests at dawn and return before dusk. They average an activity period of around 7.69 hours a day. (Emmons, 1975; Emmons, 1980; Kingdon, 2015)

Home Range

Western palm squirrels can have a home range of 21 hectares that surrounds the parent tree housing their den, which is considered quite large. They do not defend territories. (Emmons, 1975; Kingdon, 2015)

Communication and Perception

Although western palm squirrels are considered solitary animals, they do communicate with one another. They have two types of calls that have different intensities. The low intensity call is rapid and soft, with the sound being created by the chattering of the incisor teeth. The low intensity call is softer than the high intensity call. This high intensity call is more staccato with broad-frequency pulses. By having two different types of calls, a western palm squirrel can communicate can indicate how close the danger is to them.

Upon hearing the call, a squirrel typically climbs so that it has a better vantage point and will be able to tell where exactly the danger is. A squirrel will also climb to a higher support so that it can make the call. Upon creating the high intensity call, the base of the tail is wagged rapidly a few times and then slowly for a short while. If the squirrel does not climb to a higher vantage point to call, then its tail is held horizontal to the ground and does not wag. (Emmons, 1975; Kingdon, 2015)

Food Habits

Western palm squirrels typically feed on fallen seeds and fruit, and they occasionally eat insects. They are specifically known for eating the nuts of Panda oleosa, and piles of shells from these nuts can be used to indicate whether these squirrels are present in that area. This species of squirrel has a very peculiar way of opening these tough-shelled nuts: they saw the nuts in half across the middle using their teeth. Some of these Panda nuts are buried so that the Palm Squirrel can hoard them and consume them later. Typically, they are buried 15 to 20 meters away from their parent tree.

When a squirrel is feeding on these nuts, it will climb to a low feeding perch so that it has a better vantage point and can see approaching predators. These feeding perches are typically around 0.5 to 1.5 meters off the ground. Because the nuts are very hard and must be sawed through, feeding on them can be a noisy process. This compromises their ability to hear predators approaching, so they must increase their vantage point so they will be able to better see the predators. (Emmons, 1975; Emmons, 1980; Ikpegbu, et al., 2014; Kingdon, 2015)

  • Animal Foods
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit

Predation

To avoid predators, western palm squirrels make their dens in tree cavities that are off the ground with narrow entrances that are barely big enough for them to fit into. This prevents exposure to both large predators from entering and predators that cannot climb from attacking them while they are in their nests. Once a predator is seen, these squirrels will call out by using either their low intensity call to announce a less dangerous threat or their high intensity call to inform others of a more threatening attack. Typically, they will climb up to a higher perch to make these calls. They also climb to higher perches when they are eating so that they can be aware of approaching predators.

The specific types of predators that attack Epixerus ebii have not been characterized. Predators of other squirrels found in its range include raptors, large snakes, and mammalian carnivores such as genets and African golden cats. (Emmons, 1978; Emmons, 1979; Emmons, 1980; Grubb, 2008; Kingdon, et al., 2013)

Ecosystem Roles

Because western palm squirrels bury the nuts they find, particularly Panda oleosa nuts, they are responsible for dispersing these trees. By burying the nuts and forgetting about them or not being able to make it back to retrieve them, they are essentially planting them.

They are also believed to be prey for species of raptors, foxes, and genets. It is not currently known whether they act as hosts for any other species. (Emmons, 1979; Emmons, 1980; Kingdon, 2015)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Humans use western palm squirrels as a source of meat occasionally, when larger prey items are scarce. These squirrels also distribute the nuts of a tree species that that grows fruits that can be consumed by humans, giving them another food source. (Emmons, 1980; Kingdon, et al., 2013)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no known negative economic impacts caused by western palm squirrels. (Kingdon, 2015)

Conservation Status

Western palm squirrels are extremely skittish around humans, and difficult to observe. Because of this, their exact density is unknown, so approximations have been made in order to determine the conservation status. The species is currently rated as "Least Concern" by the IUCN, based on the large range and presumed large population. However, exact numbers are not known, trends in population size are not known, and the species' dependence on primary forest makes it vulnerable to deforestation. (Grubb, 2008; Kingdon, et al., 2013)

Contributors

Kelsie Carlson (author), Indiana University - Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, George Hammond (editor), Animal Diversity Web Staff.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

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.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

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.

young precocial

young are relatively well-developed when born

References

Emmons, L. 1975. Ecology and Behavior of African Rainforest Squirrels. Ithaca, NY: Cornell University.

Emmons, L. 1980. Ecology and Resource Partitioning among Nine Species of African Rain Forest Squirrels. Ecological Monographs, 50: 31-54.

Emmons, L. 1979. Observations on Litter Size and Development of Some African Rainforest Squirrels. Biotropica, 11: 207-213.

Emmons, L. 1978. Sound Communication among African Rainforest Squirrels. Zeitschrift für Tierpsychologie, 47: 1-49.

Gouat, P., I. Yahyaoui. 2001. Reproductive Period and Group Structure Variety in the Barbary Ground Squirrel Atlantoxerus getulus. Lecture at the University of Paris, 13: 343-352.

Grubb, P. 2008. "IUCN Red List of Threatened Species" (On-line). Accessed February 29, 2016 at http://www.iucnredlist.org/details/7899/0.

Hayssen, V., A. van Tienhoven, A. van Tienhoven. 1993. Asdell's Patterns of Mammalian Reproduction: A Compendium of Species-Specific Data. Journal of Mammalogy, 75: 231-233.

Ikpegbu, E., U. Nlebedum, O. Nnadozie, I. Agbakwuru. 2014. The Liver Micromorphology of the African Palm Squirrel Epixerus ebii. International Journal of Morphology, 32: 241-244.

Kingdon, J., D. Happold, T. Butynski, M. Hoffmann, M. Happold, J. Kalina. 2013. Mammals of Africa. New York: Bloomsbury.

Kingdon, J. 2015. The Kingdom Field Guide to African Mammals. London: Bloomsbury.

Lidicker, W. 1989. Rodents: A World Survey of Conservation Concern. Gland, Switzerland: IUCN.

Waterman, J. 1998. Mating Tactic of Male Cape Ground Squirrels, Xerus inauris: Consequences of Year-Round Breeding. Journal of Animal Behavior, 56: 459-466.

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