Xerus inaurisSouth African ground squirrel

Geographic Range

Cape ground squirrels are found in regions ranging from southern Africa in Namibia and Botwsana to South Africa. (Skurski and Waterman, 2005)

Habitat

Cape ground squirrels live in tropical regions. They prefer dry environments, such as savannas and grasslands. They are also found in the Kalahari Desert, which has an elevation of 600 to 1200 m. Cape ground squirrels live in burrows, which protect them from extreme weather conditions as well as from predation. They do not hibernate. (O’Meara, et al., 2009; Skurski and Waterman, 2005)

  • Range elevation
    600 to 1200 m
    1968.50 to 3937.01 ft

Physical Description

Cape ground squirrels have coarse, short hair. The color of the skin is black. On the back of the body, individuals vary between dark and light shades of a reddish brown. The underbody, limbs, neck, and face are white. They have small ears. A defining characteristic is the extended white tail that is almost as large as the body. Females and males are dimorphic, differing in length and mass. Adult males average 452 to 476 mm, while females are around 435 to 446 mm in length. The mass of males is 423 to 649 g and females are 444 to 600 g. Average mass is 528.5 g. Basal metabolic rate has been calculated at 1.7750 W. (de Magalhaes, et al., 2009; Skurski and Waterman, 2005)

  • Sexual Dimorphism
  • male larger
  • Range mass
    423 to 649 g
    14.91 to 22.87 oz
  • Average mass
    528.5 g
    18.63 oz
  • Range length
    435 to 476 mm
    17.13 to 18.74 in

Reproduction

Cape ground squirrels mate throughout the year and are promiscuous. Both males and females mate with multiple partners. When females become receptive, interactions with males occur immediately after leaving the burrow in the morning. Females are in estrous multiple times a year. Estrous does not occur at regular intervals, instead, spontaneous ovulation is thought to occur. Males search for females in estrous and copulate right away or chase females into burrows and mate there. Researchers found that mating took place both above and below ground. Waterman (1998) also found that the minimum time needed to ejaculate was 25 seconds. Dominant males have more mates and gain priority access in mating order. Male to male competition occurs, yet no injuries have been reported. Researchers concluded that aggressive fighting is too costly because a male would be unable to mate if injured. Instead, males approach each other side to side and use a non-aggressive leaping display in which the backs are arched and heads are facing each other. Males must use competitive searching to find females in estrous. Since dominant males have more experience, they find females first. Males also constantly disrupt mating in order to mate with the particular female that they have not mated with yet. When this happens, the disrupted male returns later to finish mating with the same female. Even though mating disruptions happen frequently, males rarely guard their mate. (Waterman, 1998)

Breeding takes place all year long with a peak in the winter. Cape ground squirrels live in social groups with around 3 or 4 females. However, only one female is in estrous at a time. Once a female mates with a male, there is an average of a 48 day gestation period that ranges from 42 to 49 days. Females have a litter of 1 to 3 pups that are altricial; they are blind and naked when they are born. Pups come out of the burrow at the age of 45 days. Females nurse the young for an average of 52 days, so the pups eat solid food approximately 7 days after leaving the burrow. At the age of 153 days, the pups have reached adult size of 570 g. Pups do not reach sexual maturity until 8 months for males and 10 months for females. Once males reach sexual maturity, they disperse from the burrow, while females remain in the social group. (Skurski and Waterman, 2005)

  • Breeding interval
    Cape ground squirrels breed year around, with a peak in the winter.
  • Breeding season
    Breeding occurs throughou the year. Only one female is in estrous at a time in a social group.
  • Range number of offspring
    1 to 3
  • Range gestation period
    42 to 49 days
  • Average gestation period
    48 days
  • Average weaning age
    52 days
  • Average time to independence
    153 days
  • Average age at sexual or reproductive maturity (female)
    10 months
  • Average age at sexual or reproductive maturity (male)
    8 months

Cape ground squirrels offspring are atricial at birth and need parental care until they are independent. Females protect their offspring in the burrows. Once pups are 45 days of age, they can leave the burrows. Females provide food for their young through nursing until pups are 52 days old. After 52 days, pups leave the burrow to forage on their own. Pups reach full adult size at 153 days. Once males reach sexual maturity at 10 months, they no longer associate with the social group. Once females reach sexual maturity at 8 months, they stay with the social group and continue to associate with the mother. Males are found to have no involvement in parental care. (Skurski and Waterman, 2005)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • post-independence association with parents

Lifespan/Longevity

Little is known about the lifespan of this species in the wild. However, the longest lifespan found in captivity is 11.5 years. (de Magalhaes, et al., 2009; de Magalhaes, et al., 2009)

  • Range lifespan
    Status: captivity
    11.5 (high) years

Behavior

Cape ground squirrels are diurnal animals that live in burrows. They typically leave the burrow in the morning, often a couple of hours after sunrise. On arising, they groom themselves and lie stomach down in the sun. After a short while, ground squirrels begin foraging in the grasslands. In the afternoon hours, they tend to groom and socialize. In the hot, afternoon sun, these squirrels raise their large, fluffy tails to act as an umbrella for shade. They escape to burrows to help regulate body temperature. Their repeated escape and emergence from burrows during the day is called “shuttling”. Cape ground squirrels typically return to burrows at night. (Fick, et al., 2009; Skurski and Waterman, 2005)

Female Cape ground squirrels live in social groups of 1 to 4 females with their offspring. Females in social groups share living quarters and often groom each other. Males live separately, with up to 19 group members. Females have no social hierarchy, yet males have a strict linear hierarchy according to age. While a dominance hierarchy exists, males still groom each other regardless of rank. When competition occurs, males do engage in physical fights, using leaping displays instead. (Fick, et al., 2009; Skurski and Waterman, 2005)

  • Average territory size
    700 m^2

Home Range

Cape ground squirrels do not wander far from burrows while foraging. Burrows are arranged in separate bunches and some are connected underground. Researchers found 60 burrow entrances in a 700 square meter area and groups of burrows were separated by 200 m. (Waterman and Roth, 2007)

Communication and Perception

Cape ground squirrels communicate with one another vocally. Alarm calls are used to warn each other of a threat. When the threat is extreme, squirrels let out a high pitched shrill. If the threat is less intense, a medium pitch is used. Young squirrels use chirping calls during play. Young squirrels also use squeaks to advertise their disapproval when their mother handles them. During daily interactions, ground squirrels use growls to communicate. Like most other mammals, it is likely that they use olfaction extensively in communication as well. (Skurski and Waterman, 2005)

Food Habits

Cape ground squirrels eat bulbs, grasses, herbs, insects, seeds, and shrubs. (Skurski and Waterman, 2005)

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

Predation

Known predators of Xerus inauris are black-backed jackals (Canis mesomelas). Belton et. al (2007) found that Cape ground squirrels took longer to come out of their burrow when black-backed jackals feces was present. Once out of the burrow, squirrels investigated the feces and searched the area for the predator with extreme caution. This confirms that Cape ground squirrels use olfactory cues to detect predators. Puff adders (Bitis arietans) and monitor lizards (Varanus exanthematicus) are also known predators of Cape ground squirrels. Their social living, cryptical coloration, and vigilance help to protect them from predation.

When a predator approaches, a male and female squirrel will “mob” attack the predator. This “mobbing” involves putting their tails between their own bodies and the predator’s body. This is only a defense, because if the predator attacks, Cape ground squirrels will flee. (Belton, et al., 2007; Skurski and Waterman, 2005; Waterman and Roth, 2007)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Cape ground squirrels benefit their environment when they create burrows because meerkats (Suricata suricatta) and yellow mongooses (Cynictis penicillata) use them as protection from predation and to regulate body temperature. Cape ground squirrels also increase visibility when they remove plants from the surface while they eat. Cape ground squirrels have a mutualistic relationship with meerkats. Meerkat alarm calls warn squirrels of potential danger from predators. In turn, Cape ground squirrels provide burrows. A wide variety of parasites are known from Cape ground squirrels. (Skurski and Waterman, 2005; Waterman and Roth, 2007)

  • Ecosystem Impact
  • creates habitat
Mutualist Species
Commensal/Parasitic Species

Economic Importance for Humans: Positive

Cape ground squirrels are interesting and important members of native ecosystems.

Economic Importance for Humans: Negative

Cape ground squirrels carry rabies and occasionally damage crops. (Skurski and Waterman, 2005)

Conservation Status

According to the IUCN Red List, this species has maintained a steady population trend with no specific threats. (Griffin and Coetzee, 2008)

Contributors

Taryn Richards (author), James Madison University, Suzanne Baker (editor, instructor), James Madison University, Tanya Dewey (editor), Animal Diversity Web.

Glossary

Ethiopian

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

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.

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.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

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.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

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

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

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.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

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.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

polygynandrous

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

sedentary

remains in the same area

sexual

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

social

associates with others of its species; forms social groups.

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.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

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.

year-round breeding

breeding takes place throughout the year

References

Belton, L., N. Ball, J. Waterman, P. Bateman. 2007. Do Cape ground squirrels (Xerus inauris) discriminate between olfactory cues in the faeces of predators versus non-predators?. African Zoology, 42(1): 135-138.

Fick, L., T. Kucio, A. Fuller, A. Matthee, D. Mitchell. 2009. The relative roles of the parasol-like tail and burrow shuttling in thermoregulation of free-ranging Cape ground-squirrels, Xerus inauris.. Comparative Biochemistry and Physiology, 152: 334-340.

Griffin, M., N. Coetzee. 2008. "Xerus inauris" (On-line). 2008 IUCN Red List of Threatened Species. Accessed April 27, 2009 at www.iucnredlist.org.

O’Meara, P., A. Lemon, N. Winchester. 2009. "South Africa" (On-line). Microsoft® Encarta® Online Encyclopedia. Accessed April 27, 2009 at http://encarta.msn.com.

Skurski, D., J. Waterman. 2005. Mammalian Species: Xerus inauris. American Society of Mammalogists, 781: 1-4. Accessed April 22, 2009 at http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i1545-1410-781-1-1.pdf.

Waterman, J. 1998. Mating tactics of male Cape ground squirrels, Xerus inauris: consequences of year-round breeding. Journal of Animal Behaviour, 56: 459-466.

Waterman, J., J. Roth. 2007. Interspecific associations of Cape ground squirrels with two mongoose species: benefit or cost?. Behavioral Ecology and Sociobiology, 61(11): 1675-1683.

de Magalhaes, J., A. Budovsky, G. Lehmann, J. Costa, Y. Li, V. Fraifeld, G. Church. 2009. The Human Ageing Genomic Resources: online databases and tools for biogerontologists. Aging Cell, 8(1): 65-72.