Xerus inauris

Geographic Range

Cape ground squirrels are found in regions ranging from southern Africa in Namibia and Botwsana to South Africa.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

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.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune
• savanna or grassland savanna or grassland

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

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.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

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.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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.

• Parental Investment
• altricial 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.

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.

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.

• Key Behaviors
• terricolous
• fossorial fossorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• social social
• dominance hierarchies dominance hierarchies

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.

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.

• Communication Channels
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Cape ground squirrels eat bulbs, grasses, herbs, insects, seeds, and shrubs.

• Primary Diet
• omnivore omnivore

• 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.

• Anti-predator Adaptations
• cryptic 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.

• Ecosystem Impact
• creates habitat

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.

• Negative Impacts
• injures humans
  • carries human disease
• crop pest
• causes or carries domestic animal disease causes or carries domestic animal disease

Conservation Status

According to the IUCN Red List, this species has maintained a steady population trend with no specific threats.

Additional Links

Encyclopedia of Life

Contributors

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

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

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

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.