Cape Ground Squirrel
| Cape Ground Squirrel | |
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| Cape Ground Squirrel (Xerus inauris) | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Sciuridae |
| Genus: | Xerus |
| Subgenus: | Geosciurus |
| Species: | X. inauris |
| Binomial name | |
| Xerus inauris (Zimmerman, 1780) |
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| Cape Ground Squirrel range | |
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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[edit] Description
The Cape ground squirrel has bristly and coarse short hair that covers its body and lacks underfur. The dorsal parts of the fur are cinnamon colored and have lighter and darker variation among individuals.[2] The face, underbelly, sides of neck and ventral parts of limbs are white, while the skin is black. The ground squirrel has small exterior ear pinnae. The sides of its body each have a white stripe that extends from shoulder to thigh. The eyes have white lines around them. The tail is flattened dorsoventrally and is cover with white hair and 2 black bands at the base.[3] The Cape ground is sexually dimorphic, although it is not pronounced. Males usually weigh 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] There are nine transverse intermolar palatal ridges that are interrupted at midline to form a furrow with two continuous ridges anterior to the molar.[2] The females have two pairs of mammary: one being inguinal and the other being abdominal.[5] The glans penis of the males are relatively large with a well-developed terminal baculum and turns downwards at the apex.[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]
[edit] Distribution
The Cape ground squirrel lives thoughpot southern Africa; through Botswana, South Africa and Namibia.[7] It is widely distributed throughout much 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 the southwest region of Northwest province and ranges to the Free State east to 30 and in Lesotho. It can also be found in Northern Cape Province but is limited to the northeast.[3] The southernmost limit of its range is Graaff Reinet district.[3]
[edit] Behavior and ecology
Cape ground squirrels live mainly in arid or semiarid areas.[6] They prefer to live in open sandy velds and grasslands with hard ground. They can also be found in scrub on the fringes of pans, on floodplains and in cultivated fields [8] Ground squirrel are generally diurnal 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 foraging above ground.[7] For thermoregulation, ground squirrels position their bush tail towards the sun while covering the head and back.[10] Dust bathing is also done. http://www.youtube.com/watch?v=7-9ECnP5IR8&list=LL01fYfWGjUE08he6w72XB-Q&feature=mh_lolz Ground squirrels eat bulbs, fruits, grasses, herbs, insects and shrubs.[2] They do not hoard food so foraging is a daily activity.(they do bury some food items - personal observation)[6] The Cape ground squirrel gets its minimal water requirements from herbaceous vegetation and rarely drinks.[2] A ground squirrel’s daily activities are made of around 70% feeding, 15-20% vigilant behavior and around 10% social interactions.[6][9] The burrows of Cape ground squirrels are also used by meerkats and mongooses for the same reasons the squirrels use them.[11] The association between Cape ground squirrels and meerkats appears to be mutually beneficial, whereas mongooses appear to be only commensals of the squirrels.[11] Predators of grounds squirrels include jackals, snakes and monitor lizards. Ground squirrels may be able to differentiate between scent cues from the feces of predators and non-predators.[12] When threatened by predators, like snakes, ground squirrel will engage in mobbing behavior.[11][13] Multiple squirrels will lung at the predator while placing their bush tails between themselves and the predator. When the predator lunges back, all the squirrels retreat. However, multiple mobbings are usually successful in driving anyway predators.[13]
[edit] Social behavior
Social groups of Cape ground squirrels usually consist of 2-3 adult females and up to nine sub-adults of either sex[9] an well as the females’ dependant offspring.[6] Groups that have more than three females fission into smaller groups.[14] Adult males live separately from females and only join when the latter is an estrous.[9] Males live in permanent, non-aggressive groups of unrelated individuals that can number up to 19. Within a male groups, 4-5 males may form temporary subgroups that change size and composition daily.[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 home ranges encompass those of several female group home ranges and average 12.1 hectares (30 acres)[9] Within a female group, members share feeding and sleeping ranges. No dominance hierarchy exists between them. Male groups, by contrast, have distinct linear dominance hierarchies based on age and are maintained by displacements. Competition between males usually consists of nonviolent leaping displays that cause no injuries.[15] In addition, males groups are not territorial like female groups are. There is frequent immigration and emigration of members of male groups.[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 allow multiple copulations with the original males as well as subsequent males. 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.
[edit] 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; a short, shrill "bi-jo" which is the greater of the alarms and elicits the greater reactions from the others, and a medium-pitched "bi-joo" sound with is used for less imminent threats.[5] During agonistic encounters, individuals emit deep, aggressive growls.[7] Juvenile squirrels make play calls, nest-chirpings, and protest squeaks.[2]
[edit] Reproduction
Cape ground squirrel mate throughout the year[6][8][16] but peaks in mating occur in dry winter months.[2] Since females copulate with multiple males, the males' large testes are useful for sperm competition. After copulation, males will mastrubate which could function as a form of genital grooming and serve to reduce the chance of getting sexually transmitted infections.[17] Estrous lasts three hours and occurs in one female of the group at a time. Gestation last ca. 48 days[16] or 42–49 days.[5] Lactation in females begins before they give birth. A lactating female move to a separate burrow to care for their young but she returns to the groups after weaning or losing her litter.[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 and leave their natal group while female mature at 10 months and remain in their natal group.[9]
[edit] Status
There appear to be no major threats to Cape ground squirrels as a whole. It is considered to be an agricultural pest in some regions.[1] In addition, humans have used poisonous grass to control ground squirrel due to crop damage and rabies.[5] It remains common in many protected areas, including Kgalagadi Transfrontier Park in Botswana and South Africa and Etosha National Park in Namibia.[1]
[edit] 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 k Skurski, D., J. Waterman. 2005. "Xerus inauris", Mammalian Species 781:1-4.
- ^ a b c d 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 g 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
