Critter Catalog

What do they look like?

Harris' antelope squirrels are medium-sized squirrels with medium to short tails. Both males and females of this species look the same. Their average body length ranges from 229.0 to 245.8 mm, with tail lengths of 70.9 to 84.6 mm, and hindfoot lengths 37.2 to 41.6 mm. Harris' antelope squirrels have a small head with small ears. These squirrels have a grayish back, while the rest of their fur is dark-brown at the roots, white in the middle, and has brownish-white tips. There is also one narrow white stripe on both sides of their body, from the back of their shoulders to the middle of their hips. The under surface fur on their tail is a mix of white and black. In the winter, their fur is longer and softer and has a grayish tone, as compared to the pale pinkish-cinnamon color in the summer. (Best, et al., 1990; Nowak, 1999)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Average mass

  122 g

  4.30 oz

• Average mass

  126 g

  4.44 oz

  AnAge

• Range length

  229.0 to 245.8 mm

  9.02 to 9.68 in

Where do they live?

Harris's antelope squirrels (Ammospermophilus harrisii) are found in southwestern parts of the United States and northwestern Mexico. They are not found north of the Grand Canyon or on the other side of the Colorado River. (Best, et al., 1990; Escalante, et al., 2007; Mantooth, et al., 2013)

• Biogeographic Regions
• nearctic
  • native

• Other Geographic Terms
• island endemic

What kind of habitat do they need?

Harris's antelope squirrels can be found in desert habitats with cacti and shrubs or in open plains deserts with gravel and sand. They can also be seen in valleys, canyons, and river bottoms. These squirrels prefer areas with dense vegetation. (Best, et al., 1990; Nowak, 1999)

• These animals are found in the following types of habitat
• terrestrial

• Terrestrial Biomes
• desert or dune

• Range elevation

  1350 (high) m

  4429.13 (high) ft

How do they reproduce?

Harris' antelope squirrels usually mate from February to March, but they may breed as early as December or January. Likewise, these squirrels sometimes continue breeding into late spring. Embryos usually begin forming within a few days of female reproductive activity. Their gestation period lasts 29 to 30 days. They usually only give birth to one litter per year, however, it is possible for a second litter to be raised. Harris' antelope squirrels show no signs of mating with the same partner within the same or different mating seasons. (Best, et al., 1990; Neal, 1965)

• Mating System
• polygynandrous (promiscuous)

Before giving birth, captive females made a round nest out of cotton material, with a covered top that had only one hole for entry and exit. Their litter sizes average 6.5 young, with an average newborn weight of 3.6 grams. On their first day, newborns lose their umbilical cord and their sex can be determined, although they lack sight and hearing. As they develop, newborns are hairless and typically have clear, pink skin, and cannot crawl right away. Within 1 week, they develop a black coloration in their fur. By 2 weeks, the white stripes observed in adults of this species can be seen. By week 3, these young squirrels have claws and front teeth. By week 4, their ears open and they are completely covered in fur. They also make noise, especially while being handled. Eyes finally open between weeks 4 and 5 and young leave their nest for the first time. The young are fully grown in 217 days. Males are ready to breed by the autumn of their first year. Females are not ready to breed until 10 to 11 months after birth. (Best, et al., 1990; Levenson, 1979; Neal, 1965)

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual

• How often does reproduction occur?

  Harris' antelope squirrels breed once every year.

• Breeding season

  Mating can begin as early as December and January for this species, but it usually occurs during mid-February to early March.

• Average number of offspring

  6.5

• Average number of offspring

  6.8

  AnAge

• Range gestation period

  29 to 30 days

• Average gestation period

  30 days

• Average weaning age

  49 days

• Range age at sexual or reproductive maturity (female)

  10 to 11 months

• Range age at sexual or reproductive maturity (male)

  14 to 19 weeks

Females raise the young by themselves. Young are unable to open their eyes for about 4 to 5 weeks. Once their eyes open, the young squirrels venture out of the nest for the first time. Harris' antelope squirrels are weaned in about 7 weeks. (Best, et al., 1990)

• Parental Investment
• female parental care

How long do they live?

In the wild, the typical lifespan of Harris' antelope squirrels ranges from 2 to 4 years. In captivity, these squirrels may live to be up to 11 years. ("Animal Fact Sheet: Harris' Antelope Squirrel", 2014)

• Range lifespan
  Status: captivity

  11 (high) years

• Typical lifespan
  Status: wild

  2 to 4 years

• Average lifespan
  Status: captivity

  10.6 years

  AnAge

How do they behave?

Harris' antelope squirrels are active throughout the day, including during the hottest hours. They do not hibernate and stay active above ground for all months of the year. These squirrels are never found in groups, they stay alone, away from other members of their species. Adults are only found together for mating. Harris' antelope squirrels often climb cacti to survey their surroundings. Their method of climbing cacti is unknown, however, they do not show scars on their soft padded feet to indicated damage from cactus thorns. These squirrels are often seen running, interspersed by irregular patterns of rest. (Best, et al., 1990; Levenson, 1979)

• Key Behaviors
• diurnal
• motile
• solitary

Home Range

Harris' antelope squirrels often create burrows for shelter. Many of these burrows are found underneath various shrubs. They also tend to situate themselves around rock-bound hills, where they can easily take shelter when necessary. These squirrels travel at an average rate of 274 m per individual. Densities in southern Arizona range from 0.24 to 0.36 per ha during the spring to late summer and 0.08 to 0.24 per ha during the autumn and winter. (Best, et al., 1990)

How do they communicate with each other?

Harris' antelope squirrels make calls and stamp their forepaws when they are alarmed. Their calls are usually a trill sound, which is unaffected by their gender, the temperature, or season. Trills are high-pitched and range in frequency based on the size of the squirrel. (Best, et al., 1990)

• Communication Channels
• tactile
• acoustic

• Perception Channels
• tactile
• chemical

What do they eat?

Harris' antelope squirrels eat seeds from desert plants and insects. The plants these squirrels eat depend on their locations. Squirrels in New Mexico feed primarily on fruits and seeds of cactus plants. Those in Arizona eat mesquite beans and yucca plant seeds. The fruit produced by prickly pear cacti are a major food source for squirrels in the Graham Mountains. Harris' antelope squirrels have also been seen burying mesquite beans. These squirrels usually stuff their mouths with seeds to transport them. They eat both within their burrows and above ground. Various other green plants and seeds are eaten by these squirrels as well. Their hands, faces, and digestive tracts are often stained by the juices of their food. Harris' antelope squirrels also feed on insects and small mammals, such as mice, that they have trapped. ("Animal Fact Sheet: Harris' Antelope Squirrel", 2014; Best, et al., 1990; Brown, 1988)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates
  • insectivore
• herbivore
  • frugivore
  • granivore
• omnivore

• Animal Foods
• mammals
• insects

• Plant Foods
• seeds, grains, and nuts
• fruit

• Foraging Behavior
• stores or caches food

What eats them and how do they avoid being eaten?

The risk of predation makes foraging more difficult for Harris' antelope squirrels. These squirrels have a much higher predation risk in open areas as compared to brushy areas. Their fur color helps keep them camouflaged as it blends in with the rocky-desert terrain, this helps them avoid predators that rely on sight. When a predator is spotted, Harris' antelope squirrels run quickly back to cover under shrubbery containing burrows, with their tail held high in the air. While running, they let out multiple alarm calls. Before escaping their predator, these squirrels often stop, let out a call and stamp their forepaws. These alarm calls have been adapted to best fit the desert environment. These high frequency calls last about 2.24 seconds and are very similar to alarm calls produced by other related species. Cactus wrens may attack Harris' antelope squirrels but they do not eat them. (Best, et al., 1990; Brown, 1988; Brown, 1989; Smith, 1970)

• These animal colors help protect them
• aposematic

• Known Predators

  • bobcats (Lynx rufus)
  • coyotes (Canis latrans)
  • kit foxes (Vulpes macrotis)

What roles do they have in the ecosystem?

Harris' antelope squirrels coexist with many other desert species. They sometimes share dens with round-tailed ground squirrels, which were built by kangaroo rats. They also compete for food with many other species due to their large diet range. By feeding mostly on seeds and fruits, Harris' antelope squirrels are good seed dispersers. These squirrels host many different parasites including fungus, nematodes, fleas, lice, and ticks. (Best, et al., 1990; Brown, 1989)

• Ecosystem Impact
• disperses seeds

Do they cause problems?

Harris' antelope squirrels have become a nuisance by raiding crops and burrowing through ditch banks in irrigated areas. They also carry parasites and may spread harmful diseases. (Best, et al., 1990; Nowak, 1999)

• Ways that these animals might be a problem for humans
• injures humans
  • carries human disease
• crop pest

How do they interact with us?

There are no recorded positive impacts of Harris' antelope squirrels on human. However, there is room for research on how these squirrels deal with the parasites that affect them. (Best, et al., 1990)

• Ways that people benefit from these animals:
• research and education

Are they endangered?

Harris' antelope squirrels are considered a species of least concern and are currently not endangered. (Timm, et al., 2013)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

Some more information...

Contributors

Matthew Haloostock (author), University of Michigan, Joanna Larson (editor), University of Michigan, Priscilla Tucker (editor), University of Michigan, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

References

2014. "Animal Fact Sheet: Harris' Antelope Squirrel" (On-line). Arizona-Sonora Desert Museum. Accessed April 18, 2014 at http://www.desertmuseum.org/kids/oz/long-fact-sheets/Harris%27s%20Antelope%20ground%20Squirrel.php.

Best, T., A. Titus, K. Caesar, C. Lewis. 1990. Ammospermophilus harrisii. Mammalian Species, 366: 1-7.

Brown, J. 1988. Patch Use as an Indicator of Habitat Preference Predation Risk and Competition. Behavioral Ecology and Sociobiology, 22: 37-48.

Brown, J. 1989. Desert Rodent Community Structure: A Test of Four Mechanisms of Coexistence. Ecological Monographs, 59: 1-20.

Escalante, T., V. Sanchez-Cordero, J. Morrone, M. Linaje. 2007. Deforestation affects biogeographical regionalization: a case study contrasting potential and extant distributions of Mexican terrestrial mammals. Journal of Natural History, 41: 965-984.

Levenson, H. 1979. Sciurid Growth Rates: Some Corrections and Additions. Journal of Mammalogy, Vol. 60: 232-235.

Mantooth, S., D. Hafner, R. Bryson, B. Riddle. 2013. Phylogeographic diversification of antelope squirrels (Ammospermophilus) across North American deserts. Biological Journal of the Linnaean Society, 109: 949-967.

Neal, B. 1965. Reproductive Habits of Round-Tailed and Harris Antelope Ground Squirrels. Journal of Mammalogy, Vol. 46: 200-206.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore, Maryland: Johns Hopkins University Press.

Smith, E. 1970. Cactus Wrens Attack Ground Squirrel. Journal of Mammalogy, Vol. 72: 363-364.

Timm, R., S. Alvarez-Castaneda, I. Castro-Arellano, T. Lacher. 2013. "Ammospermophilus harrisii" (On-line). The IUCN Red List of Threatened Species. Accessed April 20, 2014 at http://www.iucnredlist.org/details/42399/0.