Spermophilus tereticaudus communicates using whistles. Their warning is a single whistle. When emitted, it caused the other animals in the area to run to their burrows and then look around (Dunford 1977).
Communication Channels: visual ; tactile ; acoustic ; chemical
Other Communication Modes: pheromones ; scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
Spermophilus tereticaudus seems to be doing relatively well. Its habitat is not being destroyed significantly, and it seems to have a relatively good hold in its native areas (Ernest and Mares, 1987).
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
They tend to live near cultivated fields, and may eat the alfalfa and dates grown. Thus, they come into conflict with humans, but it is not much of a problem (Ernest and Mares, 1987)
These animals are not documented to have any positive economic effect on humans.
The role of these ground squirrels in their ecosystems has not been documented. Because they are omnivorous, it is likely that they have some impact on plant and insect populations. As a possible prey species, S. tereticaudus is likely to have some influence on predator populations as well. Because they dig burrows, these animals contribute to soil aeration.
Ecosystem Impact: soil aeration
Spermophilus tereticaudus is an omnivore like many other sciurids. Their diet includes a large proportion of green vegetation, but also seeds, and to a lesser extent, insects. During the spring, 80% of their diet consists of green vegetation, while 15% is represented by seeds, and 5% is represented by insects. In the summer, all of their diet is composed of green vegetation. In winter, however, their reliance on vegetation drops, and they again use seeds. When they do eat insects, they consume mainly ants, termites and grasshoppers (Ernest and Mares, 1987). They focus their diet on foods that have a high water concentration. This is necessary because they live in desert conditions, and cannot survive on dry foods. The average water content of the food they eat is 80% (Ernest and Mares, 1987).
Animal Foods: insects
Plant Foods: leaves; roots and tubers; seeds, grains, and nuts; flowers
Primary Diet: omnivore
Round tailed ground squirrels, Spermophilus tereticaudus, live in desert areas of the southwest United States and Mexico, including Arizona, California and northern Mexico. They are present in portions of the Mojave, Yuma, and Colorado deserts (Cockrum, 1982).
Biogeographic Regions: nearctic (Native )
Spermophilus tereticaudus "inhabits sandy arid regions of the Lower Sonoran Life Zone (Ernest and Mares, 1987)." It often occupies dunes and shrubs in lower flatter areas. Its burrows have been found among shrubs, and in sand of dunes, especially in areas with dense sand. Its habitats are normally characterized by extreme temperatures with low humidity (eg. -5 C to 39 C during one week)(Ernest and Mares, 1987).
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; chaparral
Range lifespan
Status: captivity: 8.9 (high) years.
Spermopilus tereticaudus is a small ground squirrel. It has a long round tail; and long, broad, and hairy hind feet (Ernest and Mares, 1987). Their fur is uniform and without markings or stripes. The underside or their body is paler, and it appears uniform from tip to tail (Hall, 1981). The summer fur color is paler and brighter than the winter pattern. Spermophilus tereticaudus molts two times per year, once in the spring and once in fall.
The skull is rounded with a short rostrum, and a post orbital process is present. Body mass fluctuates according to season, however, the average mass is 125 g (Ernest and Mares, 1987).
Range mass: 110 to 170 g.
Average mass: 125.00 g.
Other Physical Features: endothermic ; bilateral symmetry
Average basal metabolic rate: 0.501 W.
Although not specifically reported upon, it is likely that these squirrels are prey for other animals. Because of their diurnal and semi-fossorial habits, likely predators include canids, felids, snakes, and hawks. This species uses alarm signals, and these may help the squirrels evade predators.
The breeding season of Spermophilus tereticaudus starts in mid January with the enlargement of the male's testes. Females were observed to be pregnant from mid-March to late April. In mid April the testes regress, and the males are no longer capable of insemination. Gestation ranges from 25 to 35 days, and the average number of young is 6.5, with the largest litter observed containing 12. (Reynolds and Turkowski, 1972). The average mass at birth is 3.7 g, and the neonates are hairless, with eyes and ears closed. When they are 25 days old, they are capable of coordinated running, and are weaned at 5 weeks. They are sexually mature when they reach 10 to 11 months of age (Neal, 1965).
Breeding interval: These ground squirrels breed once per year.
Breeding season: Breeding occurs from January to April.
Range number of offspring: 12 (high) .
Average number of offspring: 6.5.
Range gestation period: 25 to 35 days.
Average weaning age: 5 weeks.
Range age at sexual or reproductive maturity (female): 10 to 11 months.
Range age at sexual or reproductive maturity (male): 10 to 11 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Average birth mass: 3.9 g.
Average number of offspring: 5.4.
Parental care seems to be primarily the responsibility of females. As in other ground dwelling sciurids, the neonates are altricial.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
The round-tailed ground squirrel (Xerospermophilus tereticaudus), known as "Ardillón cola redonda" in Spanish, live in the desert of the Southwestern United States and Northwestern Mexico. They are called "ground squirrels" because they burrow in loose soil, often under mesquite trees and creosote bushes.
Most round-tailed ground squirrels are very small. Weight at birth is approximately 3.9 grams (0.14 oz). Adults weigh around 125 grams (4.4 oz).[2] All have a long round tail and long, hairy hind feet. They have no fur markings, instead having a uniform sandy color, which matches the soil they burrow in. The underside of their body is usually a lighter shade. Round tailed squirrels average 204 to 278 millimetres (8.0 to 10.9 in) in length including the tail which is from 60 to 112 millimetres (2.4 to 4.4 in) long.[3]
The gestation period is 28 days. An average of 5.4 pups are born in each litter. They reach sexual maturity at 325 days. There is little information on the longevity of these animals but one wild born specimen lived to approximately 8.9 years in captivity.[2] They are prey animals for coyotes, badgers, hawks and snakes. Round-tailed ground-squirrels have also been found with the Coccidian parasite Eimeria vilasi, normally found in other rodents and Old World marmotine rodents.[4]
Ground squirrels are well-adapted to desert life, as they mainly reside in the desert regions of the southwestern United States, northeastern Baja California, and northwestern Mexico, specifically in the state of Sonora.[5] They can stay active even on the hottest of days, although they do tend to limit their activity during the heat of the afternoon sun. They live underground in the winter, typically from late August or September until January or February. They go into torpor, but do not hibernate. Males are active first in late January as they start mating in March. Ground squirrels' activity cycle makes them not aggressive or competitive. Their main activities include caring for newborn, finding better protection for their resources, and reducing predation. They chase each other and nuzzle each other.[5]
The greatest predator of the ground squirrel is a snake--the type of snake varying by the locality. As a result, ground squirrels have evolved to perform anti-snake displays to defend themselves.[6] These squirrels tend to be put on a prominent display, specifically by moving their tail back-and-forth horizontally. They also approach the predator and sometimes kick some dirt at the snake.
They have a semi-colonial social structure, and will alert others of impending danger with a high-pitched alarm call. But they will chase away other ground squirrels who get too close to their own burrow. The males are dominant during the breeding season (January through March). The females dominate during the raising of the young (March and April).[7] However, recent studies suggest that they may have a matrilineal population structure with more socialization than anticipated.[5] This means that round-tailed ground squirrels may have a greater tendency to socialize within familial groups of female squirrels.[8]
They are omnivores. The bulk of their diet is green vegetation, especially in the summer. They also eat seeds and insects (ants, termites, and grasshoppers). Most of their foods are chosen for high water content because of the shortage of available water in their environment. The average water content of the food they eat is 80%.[3]
The squirrels prefer seeds and parts of grasses and flowers, but can climb into shrubs and trees for food.[9]
The round-tailed ground squirrel (Xerospermophilus tereticaudus), known as "Ardillón cola redonda" in Spanish, live in the desert of the Southwestern United States and Northwestern Mexico. They are called "ground squirrels" because they burrow in loose soil, often under mesquite trees and creosote bushes.
