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Nelson's antelope squirrel

Ammospermophilus nelsoni

What do they look like?

The bodies of Nelson's antelope squirrels are widest in the middle. They have small, rounded ears, short legs, and short tails. The back of their heads and necks and also the outside of their legs are dull yellowish-brown or tan. Their tails have thick hair and their underside is light grey or white. They have a light-colored stripe running along the side of the body starting at the shoulder. Males are a little bit bigger than females, measuring 234 to 267 mm, but usually around 249 mm. Females are 230 to 256 mm long, and usually around 238 mm. Nelson's antelope squirrels have different summer and winter fur colors. Their fur is darker in the fall and winter. The look a lot like white-tailed antelope squirrels, but are bigger and their fur is more gray. (Best, 1999; Brown and Williams, 2006; Merriam, 1983)

  • Sexual Dimorphism
  • male larger
  • Range mass
    142 to 179 g
    5.00 to 6.31 oz
  • Average mass
    155 g
    5.46 oz
  • Range length
    230 to 267 mm
    9.06 to 10.51 in
  • Average length
    249 mm
    9.80 in
  • Average basal metabolic rate
    0.8 cm3.O2/g/hr

Where do they live?

Nelson's antelope squirrels only live in California. They lives in the lowest parts of the San Joaquin valley, the Cuyama and Panoche valleys in San Luis Obispo county, and the Carrizo and Elkhorn plains. (Best, et al., 1990; Taylor, 1918)

What kind of habitat do they need?

Nelson's antelope squirrels are found in low, hot deserts. In North America, their habitats are found in Texas, New Mexico, Arizona, Nevada, and California. They live in dry grasslands and places with lots of shrubs. They can live in places with just a few or some shrubs and usually live with plants that live in dry environments. They like soils with clay, sand, and silt that are about 50 to 1100 meters elevation. They use burrows of kangaroo rats, so they might only live where there are kanagaroo rats. (Grinell and Dixon, 1918; Hawbecker, 1953; Merriam, 1898; Whitaker, et al., 2008)

  • Range elevation
    50 to 1100 m
    164.04 to 3608.92 ft

How do they reproduce?

Both male and female Nelson's antelope squirrels have multiple mates. Usually they find mates within the area where they usually live, but females will also travel up to 1 km away looking for a mate. ("Five Year Status Report- Ammospermophilus nelsoni", 1987; Hawbecker, 1947)

Nelson's antelope squirrels breed from late winter to early spring. The young develop inside the mother for 26 days. Then, females give birth in burrows underground. They have 6 to 11 young at a time, but usually around 9. The young stay underground for about the first 30 days after they are born. They drink their mother's milk. Sometimes they start eating solid food before they come out of the burrow, and other times not until after. Females get the young to stop drinking milk by refusing to give it to them and returning to the burrow less often. Males can breed earlier in their lives than females. (Best, et al., 1990; Best, 1999; Macdonald, 2009)

  • How often does reproduction occur?
    Nelson's antelope squirrels breed once annually.
  • Breeding season
    Nelson's antelope squirrels breed from late winter to early spring.
  • Range number of offspring
    6 to 11
  • Average number of offspring
    9
  • Range gestation period
    25 to 30 days
  • Average gestation period
    26 days
  • Range weaning age
    30 (high) days
  • Average weaning age
    15 days
  • Range time to independence
    3 to 4 weeks
  • Average age at sexual or reproductive maturity (female)
    377 days
  • Average age at sexual or reproductive maturity (male)
    377 days

Young Nelson's antelope squirrels can't feed themselves right after they are born. Females give them milk and teach them to eat solid food, and males don't play a big role in caring for them. Mothers get their young to stop drinking their milk by staying farther away and not responding to them. Even after they stop drinking milk, mothers stay in contact by visiting their young and calling to them. (Best, et al., 1990)

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

How long do they live?

In the wild, Nelson's antelope squirrels usually live for less than 1 year. Their babies and young are much more likely to die. They can live about 4 years in captivity, and the longest one ever lived in captivity was 5.7 years. About 80% of them die every year. They average lifespan is just 8 months. (Best, et al., 1990; Hawbecker, 1975)

  • Range lifespan
    Status: captivity
    5.7 (high) years
  • Average lifespan
    Status: wild
    8 months
  • Average lifespan
    Status: captivity
    4 years

How do they behave?

Nelson's antelope squirrels live in small family groups of 6 to 8 squirrels. They are closely related to white-tailed antelope squirrels, who have strict social organization. They keep up their social organization using body language and fighting. Nelson's antelope squirrels are very similar to them in a lot of ways, and might do this too. ("Five Year Status Report- Ammospermophilus nelsoni", 1987; Belk and Smith, 1991; Best, et al., 1990; Best, 1999; Grinell and Dixon, 1918; Hawbecker, 1947; Hawbecker, 1953; Hawbecker, 1975)

  • Average territory size
    0.044 km^2

Home Range

Males and females usually live and travel in an area about 4.4 hectares. They tend to clump together within these areas in the best parts of their habitat. The farthest away from their home area males travel is 1,260 m and the fatherst away from their home area females travel is 900 m. (Best, et al., 1990)

How do they communicate with each other?

Nelson's antelope squirrels mostly use hearing, smell, and sight. They look around before deciding to leave their burrows. They use their sense of smell to decide if there is danger, to find food, and communicate. They make alarm calls to warn others about nearby predators, especially if they are in closed-off areas. They make low-pitched trills that are actually made by shaking their body instead of their voice. Females also make this noise to communicate with their young. Nelson's antelope squirrels twitch their tails quickly when they are frightened or excited. (Best, et al., 1990; Best, 1999; Bolles, 1988)

What do they eat?

Nelson’s antelope squirrels eat both animals and plants. Their biggest sources of food are insects, green plants, and seeds. They sometimes eat other small animals. They eat rodents, lizards and other Nelson's antelope squirrels that have died. They prefer to eat plants with a lot of water in them, since they don't live near water. Some plants they prefer are red-stemmed filaree and red brome. Other plants they eat are ephedra, clover, and locoweed. If there aren't many plants available that have a lot of water, they eat turpine weed. When plants and insects aren't available, they eat seeds. Nelson's antelope squirrels squat on their back legs with their tail up to eat, holding food in their front paws. (Hawbecker, 1947; Macdonald, 2009)

  • Animal Foods
  • reptiles
  • carrion
  • insects
  • Plant Foods
  • leaves
  • seeds, grains, and nuts

What eats them and how do they avoid being eaten?

Nelson's antelope squirrels warn each other about predators and also avoid them. They hide in burrows of kangaroo rats, and check their surroundings carefully before they come out. Above ground, they hide in shrubs, and their light brown fur camouflages them in the desert. When they search for food, they stay close to the ground and move with short, quick jumps. Nelson's antelope squirrels use their sense of smell to get away from danger quickly. They communicate to each other about predators using alarm calls. They may also be able to understand warning calls of birds like horned larks and white-crowned sparrows. Their most important predators are American badgers, who dig into the burrows to eat both young and adults. They are also eaten by coyotes and kit foxes. ("Five Year Status Report- Ammospermophilus nelsoni", 1987; Best, et al., 1990; Brown and Williams, 2006)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Nelson's antelope squirrels are eaten by medium-sized predators. They get parasites inside and outside their bodies. They get tapeworms, roundworms (called Spirura infundibuliformis and Physaloptera spinicauda), and also thorny-headed worms. Outside their bodies, they get fleas and ticks. Nelson's antelope squirrels benefit from kangaroo rats, because they use their burrows. They further impact their habitat by continuing to burrow. They also collect seeds and disperse them. (Best, et al., 1990)

  • Ecosystem Impact
  • disperses seeds
  • creates habitat
Species (or larger taxonomic groups) that are mutualists with this species
Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • cestodes (Hymenopelis citelli)
  • nematodes (Spirura infundibuliformis)
  • nematodes (Physaloptera spinicauda)
  • acanthocephalans (Moniliformes dubius)
  • fleas (Siphonaptera)
  • ticks (Ixodes)

Do they cause problems?

Nelson's antelope squirrels can get infected with diseases like western equine encephalomyelitis, St. Louis encephalitis, Powassan virus, and Modoc virus. However, they have never spread disease to humans. (Best, et al., 1990)

How do they interact with us?

Nelson’s antelope squirrels don't usually live close to humans. They eat insects that can be pests and also spread the seeds they gather and store. (Belk and Smith, 1991; Hawbecker, 1947)

Are they endangered?

Nelson’s antelope squirrels are endangered, according to the IUCN Red List. A lot of their habitat has been destroyed because of farming and humans building bigger cities. They are also affected when animals raised by humans eat the plants they do, and by chemicals that are used to kill rodents and insects. California's Endangered Species Recovery Program has a list of ways to conserve them, like protecting their habitat and reintroducing them into protected areas. ("Five Year Status Report- Ammospermophilus nelsoni", 1987; Best, et al., 1990; Brown and Williams, 2006; Grinell and Dixon, 1918)

Some more information...

There are a lot of fossils of the relatives of Nelson's antelope squirrels. They probably became their own species between 5.3 and 23 million years ago. (Best, et al., 1990; Hawbecker, 1953)

Contributors

Divya Balaji (author), Yale University, Eric Sargis (editor), Yale University, Rachel Racicot (editor), Yale University, Tanya Dewey (editor), University of Michigan-Ann Arbor, Catherine Kent (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that generate their own body heat through metabolic processes.

female parental care

parental care is carried out by females

folivore

an animal that mainly eats leaves.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scavenger

an animal that mainly eats dead animals

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

California Department of Fish and Game. Five Year Status Report- Ammospermophilus nelsoni. EW87. Turlock: Calif. Dep. of Fish and Game, Nongame Bird and Mammal Sec. rep. 1987.

Belk, M., D. Smith. 1991. Ammospermophilus leucurus. Mammalian Species, 368: 1-8.

Best, T. 1999. Ammospermophilus nelsoni. Pp. 407-408 in D Wilson, S Ruff, eds. Smithsonian Book of North American Mammals, Vol. 1999, 1999 Edition. British Columbia: UBC press.

Best, T., A. Titus, C. Lewis, K. Caesar. 1990. Ammospermophilus nelsoni. Mammalian Species, 367: 1-7.

Bolles, K. 1988. The Evolution and variation of antipredator vocalizations of antelope squirrels. Zeitschrift für Säugetierkunde, 53: 129-147.

Brown, N., D. Williams. 2006. "Endangered Species Recovery Program" (On-line). San Joaquin antelope squirrel Ammospermophilus nelsoni. Accessed April 30, 2012 at http://esrp.csustan.edu/speciesprofiles/profile.php?sp=amne.

Cypher, B. 2001. Spaciotemporal Variation in Rodent Abundance in the San Joaquin Valley. The Southwestern Naturalist, 46/1: 66-75.

Grinell, J. 1933. Review of the Recent mammal fauna of California. Berkeley, California: University of California.

Grinell, J., J. Dixon. 1918. Natural History of the Ground Squirrels of California. Sacramento, California: California State Printing Office.

Hawbecker, A. 1975. The Biology of Some Desert Dwelling Ground Squirrels. The Hague, Netherlands: Dr. Junk, b.v.

Hawbecker, A. 1953. Environment of the Nelson Antelope Ground Squirrel. Journal of Mammalogy, 34/3: 324-334.

Hawbecker, A. 1947. Food and Moisture Requirements of the Nelsons Antelope Ground Squirrel. Journal of Mammalogy, 28/2: 115-125.

Hawbecker, A. 1958. Survival and Home Range in the Nelson’s antelope squirrel. Journal of Mammalogy, 39: 207-215.

Heller, C., J. Henderson. 1976. Hypothalamic Thermosensitivity and Regulation of Heat Storage Behavior in a Day-active Desert Rodent Ammospermophilus nelsoni. Journal of Comparative Physiology, 108: 255-270.

Macdonald, D. 2009. Rodentia. Pp. 128-166 in D Macdonald, ed. The Encyclopedia of Mammals, Vol. 2009, 2nd revised Edition. Oxford: Oxford University Press.

Merriam, H. 1898. Life Zones and Crop Zones of the United States. Washington D.C: Government Printing Office.

Merriam, H. 1983. Descriptions of eight new ground squirrels of the genera Spermophilus and Tamias from California, Texas, and Mexico. Proceedings of the Biological Society of Washington, 8: 129-138.

Taylor, W. 1918. A New Spermophile from the San Joaquin Valley California with notes on Ammospermophilus nelsoni nelsoni Merriam. Berkeley, Califronia: University of California Press.

Tevis, L. 1953. Stomach Contents of Chipmunks and Mantled Squirrels in Northeastern California. Journal of Mammalogy, 34/3: 316-324.

Whitaker, J., G. Hammerson, D. Williams. 2008. "Ammospermophilus nelsoni" (On-line). IUCN Red list of Threatened Species. Accessed April 30, 2012 at http://www.iucnredlist.org/apps/redlist/details/1149/0.

 
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Balaji, D. 2012. "Ammospermophilus nelsoni" (On-line), Animal Diversity Web. Accessed April 25, 2014 at http://www.biokids.umich.edu/accounts/Ammospermophilus_nelsoni/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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