Overview
Distribution
Range Description
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Geographic Range
Cape ground squirrels are found in regions ranging from southern Africa in Namibia and Botwsana to South Africa.
Biogeographic Regions: ethiopian (Native )
- 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.
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Physical Description
Morphology
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.
Range mass: 423 to 649 g.
Average mass: 528.5 g.
Range length: 435 to 476 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
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Ecology
Habitat
Habitat and Ecology
Systems
- Terrestrial
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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.
Range elevation: 600 to 1200 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland
- 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.
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Trophic Strategy
Food Habits
Cape ground squirrels eat bulbs, grasses, herbs, insects, seeds, and shrubs.
Animal Foods: insects
Plant Foods: leaves; seeds, grains, and nuts
Primary Diet: omnivore
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Associations
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
Mutualist Species:
- meerkats (Suricata suricatta)
- yellow mongooses (Cynictis penicillata)
Commensal/Parasitic Species:
- fleas (Ctenocephallaes connatus)
- ticks (Echidniphaga bradyta)
- Echnidniphaga gallinacea
- Neohaematopinus faurei
- Synosternus caffer
- Rhipicephalus theileri
- Xeroxyruis paralllela
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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.
Known Predators:
- black-backed jackals (Canis mesomelas)
- puff adders (Bitis arietans)
- monitor lizards (Varanus exanthematicus)
Anti-predator Adaptations: cryptic
- 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.
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Life History and Behavior
Behavior
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 ; chemical
Perception Channels: visual ; acoustic
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Life Expectancy
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.
Range lifespan
Status: captivity: 11.5 (high) years.
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Lifespan, longevity, and ageing
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Reproduction
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)
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.
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 birth mass: 20 g.
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.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); 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 ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); post-independence association with parents
- Waterman, J. 1998. Mating tactics of male Cape ground squirrels, Xerus inauris: consequences of year-round breeding. Journal of Animal Behaviour, 56: 459-466.
- 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.
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Justification
History
- 2004Least Concern
- 1996Lower Risk/least concern(Baillie and Groombridge 1996)
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Conservation Status
According to the IUCN Red List, this species has maintained a steady population trend with no specific threats.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
- Griffin, M., N. Coetzee. 2008. "Xerus inauris" (On-line). 2008 IUCN Red List of Threatened Species. Accessed April 27, 2009 at www.iucnredlist.org.
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Trends
Population
Population Trend
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Threats
Threats
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Management
Conservation Actions
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Relevance to Humans and Ecosystems
Benefits
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
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Economic Importance for Humans: Positive
Cape ground squirrels are interesting and important members of native ecosystems.
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Wikipedia
Cape Ground Squirrel
The Cape Ground Squirrel (Xerus inauris) is found in most of the drier parts of southern Africa from South Africa, through to Botswana, and into Namibia.
The name Cape Ground Squirrel is somewhat misleading as it actually has a much wider area of habitation. This common name may have been arrived at to distinguish it from a tree squirrel (the Eastern Grey Squirrel) found around Cape Town, which was imported from Europe by Cecil John Rhodes.
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Description
The Cape ground squirrel has black skin with a coat is made of short stiff hairs without underfur. The fur is cinnamon on the back while the face, underbelly, sides of neck and ventral sides of limbs are white.[2] The sides of its body each have a white stripe that stretches from the shoulders to the thighs. The eyes are fairly large and have white lines around them. The pinnae is small. The tail is flattened on the back and underside and is cover with white hair and 2 black bands at the base.[3] The Cape ground's sexually dimorphism is subtle. Males usually weighing 8-12% more than females, with the former weighing 423–649 grams (0.93–1.43 lb) and the latter weighing 444–600 grams (0.98–1.3 lb).[4] The Cape ground squirrel has a total length of 424–476 millimetres (16.7–18.7 in) for males and 435–446 millimetres (17.1–17.6 in) for females.[2] The dental formula of the ground squirrel is 
.[5] The belly and groin area of the females each have two pairs of mammary glands. The glans penis of the males are large with a prominent baculum.[2] This species is notable for its enlarged testes which are around 20% of the length of the head and body.[5] Molting occurs between August and September and between March and April, once per year.[6]
Distribution
The Cape ground squirrel lives thoughout southern Africa; through Botswana, South Africa and Namibia.[7] It's range covers most of Namibia but is absent from coastal regions and the northwest.[3] Ground squirrels inhabit central and southwestern Kalahari in Botswana.[8] In South Africa, it can be found in central and north-central areas.[3]
Behavior and ecology
Cape ground squirrels live mainly in arid or semiarid areas.[6] They prefer to live in velds and grasslands with hard ground. They can also be found in scrub along pans, on floodplains and in agricultural areas.[8] Ground squirrel are generally active during the day and do not hibernate. They are burrowing animals that dig and live in clusters of burrows averaging around 700 square metres (7,500 sq ft)[9] with 2-100 entrances.[6] Burrow serve to protect the squirrel from extreme temperatures at the surface as well as predators. Nevertheless most of the day is spent feeding at the surface.[7] For thermoregulation, ground squirrels shade their head and back with their bushy tails.[10] Dust bathing is also done. Ground squirrels eat bulbs, fruits, grasses, herbs, insects and shrubs.[2] They do not hoard food so foraging is a daily activity.[6] The Cape ground squirrel usually doesn't have to drink and it gets moisture from the food it eats.[2] A ground squirrel’s daily activities are made of around 70% feeding, 15-20% being vigilant and around 10% socializing.[6][9] The burrows of Cape ground squirrels are also used by meerkats and yellow mongooses.[11] While Cape ground squirrels and meerkats appear to have a mutual relationships, mongoose and squirrel relations appear to be more commensal.[11] Predators of grounds squirrels include jackals, snakes and monitor lizards. Ground squirrels may be able to scent the differences in the dropping of predators and non-predators.[12] When threatened by predators, like snakes, ground squirrel will engage in mobbing behavior.[11][13] Multiple squirrels will rush at the predator while using their bushy tails to block it. When the predator strikes back, all the squirrels back off. However, multiple mobbings are generally successful in driving anyway predators.[13]
Social behavior
Cape ground squirrels live in groups of 2-3 adult females and a maximum of nine sub-adults of either sex[9] as well as the females’ dependant offspring.[6] Groups that have more than three females split into smaller groups.[14] Adult males live separately from females and only join when the latter is an estrous.[9] Males groups number up to 19 individuals who are not related and are not agnostic. Within a male group, 4-5 males may form temporary subgroups that change size and members each day.[2] Females groups live in separate burrow clusters. A female group’s home range is ca. 4 hectares (9.9 acres) with core areas of around 0.25 hectares (0.62 acre).[9] Home ranges can overlap however core areas are defended though agonistic behavior.[7][9] Male group live in home ranges envelop those of several female groups and average 12.1 hectares (30 acres).[9] Within a female group, members use the same feeding and sleeping ranges. No dominance hierarchy exists between them. Male groups, by contrast, have live in ages-based linear hierarchies. Competition between males usually take the form of leaping displays that cause no injuries.[15] In addition, males groups are not territorial like female groups are, and membership are very open.[2] During estrous, a female will be approached, solicited and chased by males trying to mate with her. The most dominant males get the first matings.[15] A female will mate with the same male several times. If a male has not yet mated with a female, he will disrupt the copulations she has with other males.[15] However, mate guarding is rare.
Communication
When perceiving something at a threat, ground squirrels will emit a whistle-like call as an alarm call.[5][7] The alarm call comes in two forms; the short by shrill "bi-jo" which signal serious danger, and a medium-pitched "bi-joo" sound with is used for lesser dangers.[5] During agonistic encounters, squirrels emit deep growls as signs of agression.[7] Juvenile squirrels make play calls, nest-chirpings, and protest squeaks.[2]
Reproduction
Cape ground squirrel mate reproduce year-round[6][8][16] but mating occurs mostly in dry winter months.[2] Since females copulate with multiple males, the males' large testes are useful for sperm competition. After copulation, males will masturbate which could serve to keep the genitals clean and reduce the risk sexually transmitted infections.[17] In groups, only one females at a time enters estrous which lasts around three hours. Gestation lasts around 48 days[16] or 42–49 days.[5] Lactation begins not long before the pups are born. A lactating female isolates herself in a separate burrow to care for their young but she returns to her group after weaning or if her litter is lost for some reason.[2] There are 1-3 pups in a litter.[6][16] They are born altrical, hairless and blind.[6] The pups stay in the burrows for their first 45 days. By 35 days, the eyes are open.[6] Seven days after emerging from the burrows, the pups can eat soild food. Lactation ends at around 52 days.[16] Males reach sexual maturity at eight months while female mature at 10 months. The former leave their natal groups while the latter remain.[9]
Status
The Cape ground squirrels populations does not seem to be threatened overall. In some areas, it is ppersecuted as an agricultural pest.[1] In addition, humans have used poisonous grass to control ground squirrel due to crop damage and rabies.[5] It inhabits protected areas, such as Kgalagadi Transfrontier Park in Botswana and South Africa and Etosha National Park in Namibia.[1]
References
- ^ a b c Griffin, M. & Coetzee, N. (2008). Xerus inauris. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 8 January 2009.
- ^ a b c d e f g h i j Skurski, D., J. Waterman. 2005. "Xerus inauris", Mammalian Species 781:1-4.
- ^ a b c Skinner J. D., R. H. N. Smithers. 1990. The mammals of southern African subregion, University of Pretoria.
- ^ Lynch C. D. 1983. "The mammals of the Orange Free State", Memoirs van die Nasionale Museum 18:58-60.
- ^ a b c d e f Zumpt I. F. 1970. "The ground squirrel", African Wild Life 24:115-121.
- ^ a b c d e f g h i j Herzig-Straschil, B. 1978. "On the biology of Xerus inauris (Zimmermann, 1780) (Rodentia, Sciuridae)", Zeitschrift für Säugetierkunde 43:262–278.
- ^ a b c d e Herzig-Straschil B. 1979. "Xerus inauris (Rodentia, sciuridae)-an inhabitant of arid regions of southern Africa", Folia Zoologica 28:119-124.
- ^ a b c Smithers R. H. N. 1971. The mammals of Botswana, Salisbury, Rhodesia, Museum Memoirs No. 4.
- ^ a b c d e f g h Waterman, J. M. 1995. "The social organization of the Cape ground squirrel (Xerus inauris; Rodentia: Sciuridae)". Ethology 101:130–147.
- ^ Bennett, A. F., R. B. Huey, H. John-Alder, and K. E. Nagy. 1984. "The parasol tail and thermoregulatory behavior of the Cape ground squirrel (Xerus inauris)", Physiological Zoology 57:57–62.
- ^ a b c 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.
- ^ 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.
- ^ a b Waterman, J. M. 1997. "Why do male Cape ground squirrels live in groups?" Animal Behaviour 53:809–817.
- ^ Waterman, J. M. 2002. "Delayed maturity, group fission and the limits of group size in female Cape ground squirrels (Sciuridae: Xerus inauris)", Journal of Zoology 256:113–120.
- ^ a b c Waterman, J. M. 1998. "Mating tactics of male Cape ground squirrels, Xerus inauris: consequences of year-round breeding", Animal Behaviour 56:459–466.
- ^ a b c d Waterman, J. M. 1996. "Reproductive biology of a tropical, non-hibernating ground squirrel". Journal of Mammology 77:134–146.
- ^ Waterman JM, 2010. "The Adaptive Function of Masturbation in a Promiscuous African Ground Squirrel". PLoS ONE 5(9): e13060. doi:10.1371/journal.pone.0013060
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