Xerus rutilus

Geographic Range

Unstriped ground squirrels belong to the Xerini tribe of ground squirrels characteristic of the arid country of northeastern Africa. They are endemic to East Africa and have been recorded in the region encompassed by Sudan, Tanzania and Somalia. They are native to Djibouti, Eritrea, Ethiopia, Kenya, Somalia, Sudan, Tanzania, and Uganda. Considered the most common ground squirrel of eastern Ethiopia, their geographic range in Kenya appears to be contracting in some areas, possibly as a result of displacement by the larger, more aggressive striped ground squirrels ( Xerus erythropus ). Striped ground squirrels are the only African ground squirrels that occur sympatrically with unstriped ground squirrels.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

Habitat

Unstriped ground squirrels are fossorial and associated with arid, open shrub and bush savannah, as well as riverine areas where the soil is soft for burrowing. They live in burrows at the stem bases of Salvadora thickets, low-lying stunted acacias or in long-standing zarebas. In Harar Province, Ethiopia, they are also recorded around stands of prickly pear cactus . Unstriped ground squirrels also occupy termite mounds or burrows excavated by other species. The are also found in small gullies associated with lava gravel flats and have been recorded at elevations ranging from sea level to approximately 2000 meters.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• scrub forest scrub forest

• Other Habitat Features
• agricultural agricultural

Physical Description

Unstriped ground squirrels are the smallest ground squirrels in the genus Xerus , weighing between 260 and 420 g, and measuring 200 to 255 mm in head and body length with a 120 to 225 mm long tail. They lack the longitudinal stripes characteristic of other Xerus species. Color varies somewhat according to region, but these squirrels are generally described as tawny to reddish-brown with a darker dorsum. There is considerable variation in the extent of red on the crown and also in the amount of black on the head and nape; specimens from more northern localities are paler. According to Kingdon (1974) the upper parts are heavily ticked with white, but Toschi (1945), Hollister (1919), and Dollman (1911) indicate that they may be speckled black along the back. The large eyes are ringed white and there is a white patch in front of the small, slit-like ears. The tail, colored rufous above and whitish below, is flat in appearance with long hairs projecting from each side. Dorst and Dandelot (1970) indicate that the tail is mixed with black and white. Unstriped ground squirrels have sparsely furred undersides and are described as “harsh-furred” squirrels due to the coarse, bristly texture of the pelage. They appear to molt at all times of the year. The dental formula is 1/1, 0/0, 1/1, 3/3, for a total of 20 teeth. The skull is characterized by an elongated rostrum and a small infraorbital canal. Males have a well-developed 6 mm long baculum. The chromosome number is 2n = 38.

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

• Sexual Dimorphism
• sexes alike

Reproduction

The mating system of this species is not known. However, there have been observations of mating. In this species, males exert dominance over females. A male will approach a female with a characteristic tail display which involves piloerection of the tail while it is arched over the back. Holding the tail in this position, the male rapidly approaches the female. A receptive female will respond to the male’s tail display by retreating and flicking her tail with rapid up-down movements. The female will stop occasionally to scent-mark the ground by dragging her perineal region along it. The female may also vocalize as she moves away from the male, uttering a soft chirring sound. The male follows the retreating female with the tail extended dorsally, stopping to sniff the female’s scent markings. The male then chases the female, and approaches her posterior region. The female responds by taking a submissive posture and rolling onto her side, allowing the male to approach and investigate. The male approaches and begins sniffing the female, who responds by assuming a prostrate position. The male then mounts the female by grasping behind the shoulders with both forepaws.

Drake-Brockman (1910) indicated that breeding occurs during March and April, which coincides generally with Hubert’s (1978) observation that reproduction in X. rutilus is initiated following the onset of the rainy season. However, Kingdon (1974) collected small juvenile X. rutilus throughout most months of the year and so concluded that breeding occurred throughout the annual cycle. Additionally, O’Shea (1976) indicated that males are in breeding condition throughout the year, as confirmed by testes condition and sexual behavior. It is possible that breeding season varies geographically or with climate conditions. Females likely produce two young per litter. Pregnant females containing two embryos have been collected in both Kenya and Ethiopia and one or two juveniles per female have been reported for a population near Kibwezi in south-central Kenya.

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

Prior to parturition, pregnant females establish maternity burrows at the peripheries of their home range. Former burrow systems are temporarily abandoned and old, unoccupied burrows are re-excavated for the purposes of rearing young. After 3 to 4 weeks following the emergence and weaning of young, the female abandons the maternity burrow and returns to her original burrow.

• Parental Investment
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female

Lifespan/Longevity

Longevity under natural conditions is unknown, but there is one report of a male X. rutilus captured on the Blue Nile in 1913 surviving 6 years 1 month 26 days in captivity. De Winton (1898) indicates that X. rutilus is very susceptible to cold; individuals he tamed eventually succumbed to cold weather at night. Lifespan in the wild is not reported.

Behavior

Unstriped ground squirrels are diurnal and mainly solitary. They live in isolated burrow systems, which they may occupy alone or with one other adult of either sex. They are not classified as territorial as they allow non-resident squirrels to enter their burrows, even squirrels belonging to striped ground squirrels ( X. erythropus ). There is a dominance hierarchy, with males dominant over females and juveniles. Burrows are not the centers of diurnal activity for adults. Except for periods immediately following emergence and prior to retreat, unstriped ground squirrels are not usually near the burrows. Upon emergence, they engage in sunbathing for periods up to 30 minutes. They then forage in open areas, retreating to the shade provided by bushes such as Salvadora during the heat of the day, where they continue to forage on fruit and seeds. Unstriped ground squirrels retreat to their burrows in the late afternoon. Unstriped ground squirrels also retreat to burrows during periods of extreme heat or heavy rainfall or when seeking safety. When startled, they seek the nearest cover, traveling fast with their tails down and extended. As soon as they stop, these squirrels raise the tail over their back and sits up on their haunches to confirm the danger before disappearing into the burrow. Piloerection of the tail is also observed as a general alarm reaction. Agonistic behavior in X. rutilus ranges from threat to combat. Threat by a dominant squirrel is conveyed with rough scolding chatter; subordinate ground squirrels respond with a low, gentle chirring sound. Threat may escalate to short lunges. These lunges are initiated from a variety of postures, but most frequently from a quadrupedal stance with the hind feet flat beneath the body, the back slightly arched, and one forepaw lifted off the ground. Chasing normally occurs after the chattering vocalization, but rather than ending in combat, chases tend to end abruptly when the more aggressive individual simply stops running. Actual combat is very rare in X. rutilus . The tail display that is used in mating has only been observed in adult males, but are also exhibited when adult males encounter juveniles of either sex. Juveniles respond to tail displays of adult males with the retreat-submission behaviours described for adult females. Adult males may also visually signal their sexual identity using an upright alert posture which exposes their large, conspicuous scrota. Unstriped ground squirrels exhibit behavioral thermoregulation. After foraging in hot open areas, they return to the shade and press their undersides against the ground to unload excess body heat.

• Key Behaviors
• fossorial fossorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary
• dominance hierarchies dominance hierarchies

Home Range

Unstriped ground squirrels inhabit broadly overlapping home ranges, with each home range encompassing several burrow sites. Home ranges identified during the period December to April were found to be considerably larger for males than females, ranging on average from 7.01 to 1.37 hectares, respectively. Range areas reported for the species are likely underestimated as ranges may expand during other months when food may be scarce.

Communication and Perception

Communication in unstriped ground squirrels is achieved primarily by posturing, tail positioning, and tail movement. Chirring, chattering and other vocalizations are associated with sexual encounters, threats, and submission. It is possible that chemical cues, such as pheromones, are also used in communication.

• Communication Channels
• visual visual
• acoustic acoustic

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

Food Habits

Unstriped ground squirrels are diurnal foragers. They were originally thought to consume a diet limited to roots, rice, and "jowari" (a variety of cultivated Sorghum ), but Kingdon (1974) describes a more generalist diet which includes wild roots, pods, seeds, fruit, stems, and leaves, as well as some insects. Coe (1972) indicates that more than 50 percent of their diet is dry seeds and leaves. Fruits are also consumed, including the fruits of Adansonia , Acacia , and Commiphora . De Winton (1898) identified a preference for aloe seeds. Fanson, et al. (2010) found that they appear unaffected by tannins and forage to some extent on oxalic containing foods. Unstriped ground squirrels adjust their foraging behavior relative to perceived predation risk and store food via scatter hoarding.

• Primary Diet
• herbivore herbivore
  • frugivore frugivore
  • granivore granivore

• Animal Foods
• insects

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems
• seeds, grains, and nuts
• fruit

• Foraging Behavior
• stores or caches food stores or caches food

Predation

The main predators of unstriped ground squirrels have been described for the Ngulia Rhino Sanctuary, Tsavo West National Park, Kenya. They include avian raptors, including tawny eagles ( Aquila rapax ), bateleurs ( Terathopius ecaudatus ), martial eagles ( Polemaetus bellicosus ), as well as mammalian predators including leopards ( Panthera pardus ) and black-backed jackals ( Canis mesomelas ). Although snakes were not detected in the study, these and other reptiles also likely prey on them. Unstriped ground squirrels assume an alert posture (rearing up on hind legs) when alarmed, presumably to increase their range of visual field. Anti-predator responses differ according to habitat type, but generally involve escaping to cover habitats such as bushland, using unpredictable dashing movements. Burrow systems are the major refuges used by unstriped ground squirrels when fleeing from danger.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Unstriped ground squirrels are potential prey for the rich array of avian, reptilian, and mammalian predators found in East African arid regions. Additionally, they are a host species to several types of parasite. Ectoparasites include fleas ( Synosternus somalicus ) and ticks ( Haemaphysalis calcarata ), which appears to be found only on X. rutilus . Known internal parasites include cestodes ( Catenotaenia geosciuri ) and trypanosomes ( Leishmania aethiopica ).

Economic Importance for Humans: Positive

There are no documented positive effects of X. rutilus on humans.

Economic Importance for Humans: Negative

Unstriped ground squirrels may serve as a natural reservoir of disease causing organisms and/or their vectors. Leishmania aethiopica , which causes both simple cutaneous and diffuse cutaneous leishmaniasis in humans, has been isolated from X. rutilus . Additionally, the International Union for Conservation of Nature (IUCN) indicates that X. rutilus is a significant agricultural pest species in arid parts of Kenya, with density estimates in Turkana, Kenya, reaching 848 individuals per square kilometer. Ground squirrels belonging to the genus Xerus , including X. rutilus , may cause considerable damage to crops, especially maize, ground nuts, yam, and cassava.

• Negative Impacts
• injures humans
  • carries human disease
• crop pest

Conservation Status

There appear to be no major threats to this species as a whole. The IUCN Red List classifies X. rutilus as a species of Least Concern in view of its wide distribution, presumed large population, and its tolerance for some degree of habitat modification. The species occurs in a number of protected areas (such as Samburu National Reserve, Kenya), and is unlikely to be declining fast enough to qualify for listing in a more threatened category.

Other Comments

The name Xerus is derived from the Greek xeros , meaning “dry”, either in reference to the aridity of the species’ habitat or to the bristly texture of its pelage. The epithet rutilus is Latin, and refers to a “red or golden-red” coloration. In the Somali language unstriped ground squirrels are called “dabagalleh”, which means “the possessor of a tail like a sheath or scabbard”. Kingdon (1974) identified the following local names: kindi, kidiri (Swahili), ekunyuk, ngikunyuko (Karamojong), eetata (Kiliangulu).

Fossilized remains of a terrestrial squirrel belonging to the genus Xerus was unearthed at the Pliocene site of Kossom Bougoudi in Chad. Close phylogenetic affinities of the fossil, Xerus daamsi sp. nov. and extant Xerus rutilus were determined using cladistic analysis of craniodental characters.

In 1945, Toschi indicated that mammalogists at the time recognised the seven geographical races of the species X. rutilus : X. r. rutilus Cretzchmar (including the synonymous Sciurus abessinicus Grrielin, Sciurus brachyotus Hemprich and Ehremberg, Sciurus fuscus Huet), X. r. dabagala Heuglin, X. r. intensus Thomas, X. r. rufifrons ( Sciurus xerus fiavus of A. Milne-Edward may be a synonym of X. r. rufifrons ), X. r. stephanicus , X. r. dorsalis , X. r. saturatus . Toschi (1945) proposed an additional variety, X. r. massaicus . Yalden, et al. (1976) compiled the following list of synonyms for all forms recorded from Ethiopia (some of which may represent valid subspecies): Sciurus rutilus CRETZSCHMAR, 1828, Sciurus (Xerus) brachyolus HEMPRICH & EHRENBERG, 1828, Xerus dabagala HEDGLIN, 1861, Sciurus (Xerus) fuscus HUET, 1880, Xerus saturatus NEUMANN, 1900, Xerus rutilus intensus THOMAS, 1904, Xerus rutilus stephanicus THOMAS, 1906. Kingdon (1974) identified three races, but noted that they may not reflect distinctions between neighboring populations but rather within species color variation, as color was the criterion on which the races were originally described: X. r. dorsalis (western Kenya and Karamoja), X. r. rufifrons (northern Kenya), X. r. saturatus (southeast Kenya and northeast Tanzania).

Additional Links

Encyclopedia of Life

Contributors

Isabel Martinez-Welgan (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Abebe, A., D. Evans, T. Gemetchu. 1990. The isolation of Leishmania aethiopica from the ground squirrel Xerus rutilus . Transactions of the Royal Society of Tropical Medicine and Hygiene , 84: 691.

Beaucournu, J., F. Rodhain, R. Houin. 1972. Sur quelques insectes (Siphonaptera, Anoplura) ectoparasites de mammiferes dans la Basse Vallee De L’omo (Ethiopie). Bulletin de la Societe de Pathologie Exotique , 6: 867-880.

Coe, M. 1972. The South Turkana expedition. Scientific papers IX. Ecological studies of the small mammals of South Turkana. Geographical Journal , 138: 316-338.

De Winton, W. 1898. List of the mammals obtained by Mr. R. McD. Hawker during his recent expedition to Somaliland. Proceedings of the Zoological Society of London , 1898: 761-768.

Delany, M. 1975. The rodents of Uganda . London: Trustees of the British Museum (Natural History).

Denys, C., L. Viriot, R. Daams, P. Pelaez-Campomanes, P. Vignaud, L. Andossa, M. Brunet. 2003. A new Pliocene Xerine sciurid (Rodentia) from Kossom Bougoudi, Chad. Journal of Vertebrate Paleontology , 23(3): 676–687.

Dollman, G. 1911. List of mammals from British East Africa, obtained by Mr. Robin Kemp and presented to the British Museum by Mr. C. D. Rudd, with additional notes on specimens collected and presented by Mr. A. Blaney Percival. Annals and Magazine of Natural History , series 8, vol 7: 518-529. Accessed October 21, 2013 at http://ia700402.us.archive.org/8/items/annalsmagazineof871911lond/annalsmagazineof871911lond.pdf. .

Dorst, J., P. Dandelot. 1970. A field guide to the larger mammals of Africa . London: Collins.

Drake-Brockman, R. 1910. The mammals of Somaliland . London: Hurst and Blackett.

Fanson, B., K. Fanson, J. Brown. 2010. Ecological factors affecting the foraging behaviour of Xerus rutilus . African Zoology , 45(2): 265-272.

Flower, S. 1931. Contributions to our knowledge of the duration of life in vertebrate animals. V. Mammals. Proceedings of the Zoological Society of London , 1931: 145-234.

Grubb, P., N. Oguge. 2008. "IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1." (On-line). Xerus rutilus . Accessed October 21, 2013 at www.iucnredlist.org .

Hollister, N. 1919. East African mammals in the United States National Museum, II. Rodentia, Lagomorpha, and Tubulidentata . Washington: Bulletin of the United States National Museum.

Hoogstraal, H. 1955. Notes on African Haemaphysalis ticks. II. The ground-squirrel parasites, H. calcarata Neumann, 1902, and H. houyi Nuttall and Warburton, 1915 (Ixodoidea, Ixodidae). The Journal of Parasitology , 41: 361-373.

Hubert, B. 1978. Modern rodent fauna of the Lower Omo Valley, Ethiopia. Bulletin of Carnegie Museum of Natural History , 6: 109-112.

Ingersol, R. 1968. The ecological stratification of mammals in the eastern Chercher Highlands of Harar Province, Ethiopia. Unpublished Ph.D. dissertation . Stillwater: Oklahoma State University.

Joyeux, C., J. Baer. 1945. Morphologie, evolution et position systematique de Catenotaenia pusilla (Goeze, 1782) cestode parasite de Rongeurs. Revue Suisse de Zoologie , 52: 13-51.

Key, G. 1990. Pre-harvest crop losses to the African striped ground squirrel, Xerus erythropus , in Kenya. Tropical Pest Management , 36(3): 223-229.

Kingdon, J. 1974. East African mammals, an atlas of evolution in Africa. IIB. Hares and rodents . London and New York: Academic Press.

Mace, G., P. Harvey, T. Clutton-Brock. 1981. Brain size and ecology in small mammals. Journal of Zoology , 193: 333-354.

Martin, G. 1986. Small mammals of arid savanna and montane sites in northern Kenya. Journal of Arid Environments , 11: 173-180.

Nadler, C., A. Hoffmann. 1974. Chromosomes of the African ground squirrel, Xerus rutilus (Rodentia: Sciuridae). Experientia , 30: 889-891.

O'Shea, T. 1991. Xerus rutilus . The American Society of Mammalogists , Mammalian Species No. 370: pp. 1-5, 3 figs.

O'Shea, T. 1976. Home range, social behavior, and dominance relationships in the African unstriped ground squirrel, Xerus rutilus . Journal of Mammalogy , 57: 450-460.

Pocock, R. 1923. The classification of the Sciuridae. Proceedings of the Zoological Society of London , 1923: 209-246.

Roth, V., R. Thorington Jr. 1982. Relative brain size among African squirrels. Journal of Mammalogy , 63: 168-173.

Swynnerton, G., R. Hayman. 1951. A checklist of the land mammals of the Tanganyika Territory and the Zanzibar protectorate. Journal of the East Africa Natural History Society , 20: 274-392. Accessed October 21, 2013 at http://archive.org/stream/cbarchive_101509_achecklistofthelandmammalsofth1950/XX_No.1_90__274_1950_Swynnerton#page/n107/mode/2up/search/Xerus+rutilus .

Theiler, G. 1964. Ecogeographical aspects of tick distribution. Pp. 284-300 in Ecological studies in southern Africa , Vol. Monographiae Biologicae XIV. The Hague, Netherlands: Dr. W. Junk Publishers.

Toschi, A. 1945. Two rodents from the Masai reserve. Journal of the East Africa Natural History Society , 18: 142-147.

Yalden, D., M. Largen, D. Kock. 1976. Catalogue of the Mammals of Ethiopia 2. Insectivora and Rodentia. Monitore Zoologico Italiano , Supplemento, 8:1: 1-118. Accessed October 21, 2013 at http://www.tandfonline.com/doi/abs/10.1080/03749444.1976.10736830#.UoZpesQTUkw .