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Spermophilus madrensisSierra Madre ground squirrel

By Clarence Weckman

Geographic Range

Spermophilus madrensis lives exclusively within the country of Mexico. It has been recorded in the Mexican states of Chihuahua and recently in Durango. These are both in northwestern Mexico. It is suggested that they may also be present in the states of Sinaloa and Sonora. (Best and Thomas, 1991; Servin, et al., June 1996)

Habitat

Sierra Madre mantled ground squirrels are found in pine forests at elevations ranging between 3,000 and 3,750 m. At the higher elevations it inhabits, many of the slopes have vegetative cover consisting of Juniperus, Populus, Pseudotsuga, and Pinus. The majority of the time the area is dry. However, it may snow in the higher elevations as late as May, and during the summer rain is heavy and frequent. (Best and Thomas, 1991)

  • Range elevation
    3000 to 3750 m
    9842.52 to 12303.15 ft

Physical Description

Adults have length ranging between 215 and 253 mm, with an average mass of 156 g. In the summer the head and face are hazel or sayal brown in color with the eye ring being buffy white. Cinnamon hairs lightly coat the ears. The neck and shoulders have a faint presence of cinnamon buff on their sides. General color of the upper portion of the body is cinnamon drab or fawn color. The rump and the thighs are darker and more pure in tone. The sides of the body may be cinnamon buffy or buffy white. The back is marked with dark/blackish stripes that are not very prominent. The light stripes are a dull white or a pinkish.

No information is avaiable on possible sex differences in coloration or size. (Best and Thomas, 1991)

  • Range mass
    109 to 198 g
    3.84 to 6.98 oz
  • Average mass
    154 g
    5.43 oz
  • Range length
    215 to 253 mm
    8.46 to 9.96 in

Development

Information on development for this species was not available.

Reproduction

The mating system of Sierra Madre mantled ground squirrels has not been described. However, within the genus Spermophilus, most species mate polygynously. Males compete to establish territories, then mate with the females whose home ranges overlap the male territiories. It is likely that S. madrensis has a similar mating system. (Nowak, 1999)

Information on reproduction in this species is very limited. Four females that were collected in early June contained two, four, five and five embryos each. Another that was collected in late May had five embryos. Seven females were lactating in July. (Best and Thomas, 1991)

Extrapolating from the information above, it is evident that breeding occurs in the spring, so that females are pregnant during May and June.

Gestation in the genus Spermophilus typically lasts 23-31 days. The newborn squirrels are helpless and small, weighing between 5 and 12 g, depending on species. Weaning occurs typically between 4 and 6 weeks. (Nowak, 1999)

The age of independence in these animals is unknown, as is the timing of reproductive maturity. However, because breeding is apparently seasonal, it is unlikely that animals reach sexual maturity until they are nearing one year of age.

  • Breeding interval
    These sciurids probably breed once per year.
  • Breeding season
    Breeding apparently takes place in the spring, and young are born in late spring or early summer.
  • Range number of offspring
    2 to 5
  • Average number of offspring
    4

Although there are no reports regarding the parental behavior of S. madrensis, we can make some reasonable inferences, based on the fact that they are ground squirrels.

As is true for all mammals, the female provides offspring with nourishment in the form of milk. The duration of lactation in the genus Spermophilus can be as much as 6 weeks.

In some species of Spermophilus, there is extended parental care. The young may continue to live with their mother until after their first winter. Further, in some species, females settle near their mother's home range, allowing continued association of kin. It is not known how social S. madrensis is, nor whether such kinship affiliatons occur.

Ground squirrels inhabit burrows, and it is likely that the mother maintains the burrow for her offspring. This burrow probably provides them with protection from predators as well as from the elements.

It is not known whether males contribute to parental care in this species. (Nowak, 1999)

  • Parental Investment
  • altricial
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

The potential longevity of this species is not known. However, within the genus Spermophilus, there are species in which females can live to be as much as 11 years old. Males do not seem to fare as well, and most don't live past the age of 6 years. (Nowak, 1999)

Behavior

Information on the behavior of this specific ground squirrel was not available. In general grounds squirrels are diurnal. They inhabit burrows which they excavate themselves. Many species are known to emmit alarm calls when predators are sited, and often members of a colony maintain a vigilent stance to detect predators.

The level of sociality of ground squirrels varies greatly, but most are at least somewhat social. Most ground squirrels occur in colonies, or clusters. Males may defend territories within a colony, and their territories frequently overlap with those of several females. Females often have non-overlapping home ranges.

Most species of Spermophilus have been observed entering hibernation in the winter months. However, hibernation is less certain in species occurring in the southern portion of the genus' range. It is not known whether S. madrensis hibernates or aestivates.

Many species of Spermophilus are known to store food. (Bartels and Thompson, 1993; Nowak, 1999)

Home Range

The home range size for these animals is unknown. However, for various species in the genus, reports of home ranges from 03 to 4.0 ha are available. (Nowak, 1999)

Communication and Perception

Information on this specific ground squirrel was not available. Other members of the genus are known to produce a variety of different vocalizations, apparently as part of communication within the species. Tactile communication undoubtedly occurs between a mother and her young, between mates, and between combatants when males are fighting. Also, as diurnal animals, it is likely that S madrensis uses some forms of visual communication. (Nowak, 1999)

Food Habits

Information is not available on the food habits of this species. Spermophilus roughly translates to seed loving, which suggests they eat seeds of some sort like many of their relatives.

Predation

Predation information was not available. Possible predators that are located in the area may include Canis lupus, Ursus americanus and Felis concolor. Other carnivores in the area may also feed on them. Because they are small and diurnal, S. madrensis are probably also preyed upon by hawks. (Best and Thomas, 1991)

Ecosystem Roles

Information on this specific ground squirrel was not available. As burrowers, these animals probably help to aerate the soil. As a small prey species, these squirrels undoubtedly afffect predator populations. As seed eaters, they probably play some role is dispersing seeds.

A similar species, Spermophilus lateralis, has been known to be threaten certain plants or trees. When the squirrels are abundant, they destroy seedlings by eating the cotyledons along with the endosperm. S. madrensis may have a similar affect on some species of plants. (Bartels and Thompson, 1993)

Economic Importance for Humans: Positive

None known.

Economic Importance for Humans: Negative

No negative effect of this species on humans has been reported.

Conservation Status

This species is near threatened. They do not qualify as conservation dependent, but are close to be qualifying as vulnerable.

Other Comments

Limited information can be found on this species of ground squirrel. Before 1959 it was known as Callospermophilus madrensis.

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Clarence Weckman (author), Humboldt State University, Brian Arbogast (editor), Humboldt State University.

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. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

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

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

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

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.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

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

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

soil aeration

digs and breaks up soil so air and water can get in

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).

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

Bartels, M., D. Thompson. 1993. Spermophilus lateralis. Mammalian Species, 440: 1-8.

Best, T., H. Thomas. 1991. Spermophilus madrensis. Mammalian Species, 378: 1-2.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

Servin, J., V. Sanchez-Cordero, F. Cervantes. June 1996. First Record of the Sierra Madre Mantled ground Squirrel (Spermophilus madrensis; Rodentia: Sciuridae) From Durango, Mexico. The Southwestern Naturalist, 41, no. 2: 189-190.

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