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Spermophilus perotensisPerote ground squirrel

By Meagan Rockow

Geographic Range

Perote ground squirrels (Spermophilus perotensis) are endemic to the Neotropical region and are found in Eastern Mexico within the Trans-Mexian Volcanic Belt. They live in Perote, Veracruz as well as San Salvador and Laguna de las Minas, Puebla. (Best and Gerado, 1995)

Habitat

Perote ground squirrels occupy the upper Sonoran life zone, which includes desert steppes and chaparrals. They live in large plains and sandy areas, but are threatened due to land conversion for agricultural purposes. Their habitats range in elevation from 2,340 to 2,370 m. (Best and Gerado, 1995)

  • Range elevation
    2,340 (low) m
    (low) ft
  • Average elevation
    2,370 m
    ft

Physical Description

Adult Perote ground squirrels have an average length of 7 in and reach weights between 4 and 9 oz. They have smooth, tan-grey coats with irregular dark speckling across the back. They have thin, short tails pronounced by longer hairs compared to the rest of their coats. Perote ground squirrels have four compact limbs with claws to allow for effective digging. Their forelimbs each have four clawed toes, while their hindlimbs each have five clawed toes. Their ears are not well-defined and lie smoothly alongside their heads. Their two black eyes are located on the sides of their heads, and their noses are somewhat pointed, with whiskers that help them sense their environment. To support their omnivorous diet, Perote ground squirrels have 22 teeth: four incisors, no canines, six premolars, and twelve molars. (Best and Gerado, 1995)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    113 to 255 g
    3.98 to 8.99 oz
  • Average length
    178 mm
    7.01 in

Reproduction

Perote ground squirrel females and males both breed with multiple mates, making them polygynandrous (or promiscuous). Males travel between burrows to breed with different females. Both males and females mate multiple times throughout their lives, making them iteroparous. (Ochoa, et al., 2012)

Perote ground squirrels have a late breeding season and have two litters each year. Although no specific age for sexual maturity is reported, females one-third the size of fully-grown adults can become pregnant. In their close relatives, European ground squirrels (Spermophilus citellus), both males and females are sexually mature at around 314 days. Females carry 5 to 7 embryos, each 19 mm in crown-rump length. After mating, male Perote ground squirrels may disperse from their local populations into nearby populations to continue breeding. This behavior results in a low inbreeding effect on population genetics. Perote ground squirrels have a gestation period of 28 to 30 days. They gives birth to four pups per litter, on average. ("AnAge Entry for Spermophilus Citellus", 2017; Best and Gerado, 1995; Valdéz and Ceballos, 1997)

  • Breeding interval
    Perote ground squirrels breed twice annually.
  • Breeding season
    Perote ground squirrels breed from early July to early October
  • Average number of offspring
    4
  • Range gestation period
    28 to 30 days
  • Average time to independence
    4 months

Newborn Perote ground squirrels are raised and nursed by their mothers in elaborate tunnel systems. In one study with a small sample size (n=4), juvenile Perote ground squirrels were observed to be independent from their mothers at four months of age. Exact weaning time is unknown. (Ochoa, et al., 2012)

  • Parental Investment
  • altricial
  • female parental care
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female

Lifespan/Longevity

Current research makes no mention of known natural lifespans of Perote ground squirrels because observed populations are highly impacted by predators such as prairie falcons (Falco mexicanus), long-tailed weasels (Mustela frenata), and domestic dogs (Canis lupus familiaris). Perote ground squirrels are also threatened by habitat destruction largely due to agricultural development. For these reasons, a natural lifespan for Perote ground squirrels has not been confirmed. However, their close relatives, European ground squirrels (Spermophilus citellus), have a documented maximum longevity of 6.7 years in captivity. ("AnAge Entry for Spermophilus Citellus", 2017; Valdéz and Ceballos, 1997)

Behavior

Residing in primarily treeless, shrubless, grassy habitats, Perote ground squirrels are generally active between March and November and hibernate from December to February. These periods are rough estimates, but their activity is definitely related to temperature. During active periods, Perote ground squirrels are diurnal (active during the day). Perote ground squirrels are social, working together in groups. Throughout the day they scavenge for food, construct burrows, and care for their young. At night, they retreat to underground burrows. Because they live in these burrows Perote ground squirrels are considered partially fossorial. (Montero-Bagatella, et al., 2018)

Home Range

There is no reported home range for Perote ground squirrels.

Communication and Perception

Perote ground squirrels have long whiskers protruding from their noses that help them sense their environment, especially in their underground burrows. Perote ground squirrels use sight, hearing, and smell as their main senses but are also sensitive to vibrations in the ground, which allows for increased perception in their dark burrows. They use various chirps and barks to communicate with one another. During breeding seasons, both male and female Perote ground squirrels are thought to release pheromones to attract mates. During mating season, females likely use pheromones to attract males to their burrows. Males travel to several burrows to mate with multiple females throughout one breeding season. (Best and Gerado, 1995)

Food Habits

Perote ground squirrels are primarily herbivorous, but will sometimes eat small insects. Their diet primarily consists of seeds, as their genus name, Spermophilus (“seed-lovers”), implies. (Best and Gerado, 1995)

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

Predation

Long-tailed weasels (Mustela frenata) are a prominent predator of Perote ground squirrels because these weasels can hunt ground squirrels in their burrows. Prairie falcons (Falco mexicanus) are also known to be successful predators of Perote ground squirrels because these squirrels primarily reside in habitats with few trees and shrubs to provide protection. Domestic dogs (Canis lupus familiaris) may also be considered a predator, as humans - and subsequently domestic dogs - encroachment on the native territory of Perote ground squirrels. (Best and Gerado, 1995; García-Domínguez and Priego-Hernández, 2014)

Ecosystem Roles

The interactions of Perote ground squirrels with other species of plants and animals are not well documented. However, based on their known behaviors of eating seeds and burrowing, it may be predicted that they aid in seed dispersal and soil aeration. Additionally, there may be other small burrowing animals that inhabit Perote ground squirrel burrows. This is based on the fact that other organisms have been documented to take over or coexist in European ground squirrel (Spermophilus Citellus) burrows. ("AnAge Entry for Spermophilus Citellus", 2017)

Economic Importance for Humans: Positive

There are no known positive economic benefits of Perote ground squirrels on humans.

Economic Importance for Humans: Negative

There are no known negative economic benefits of Perote ground squirrels on humans.

Conservation Status

Perote ground squirrels are considered an endangered species on the IUCN Red List. Perote ground squirrels are at risk of extinction due to their narrow geographic range, small number of remaining populations, and small population sizes, which leads to lower genetic diversity. Increased agricultural practices in their natural habitats has led to the destruction of burrowing systems, reduction of shrubs and trees that provide cover, and reduced amounts of vegetation due to livestock grazing. They have been given no special status on CITES, the U.S. Federal List, or the State of Michigan list. (García-Domínguez, et al., 2014)

Other Comments

Another scientific name for Perote ground squirrels is Xerospermophilus perotensis. Additionally, due to the small abundance and narrow territory of Perote ground squirrels, there is relatively little information that has been confirmed about the species. However, through analyzing close relatives such as European ground squirrels (Spermophilus citellus), inferences can be made about the life history of Perote grounds squirrels. (Montero-Bagatella, et al., 2018)

Contributors

Meagan Rockow (author), Colorado State University, Kate Gloeckner (editor), Colorado State University, Galen Burrell (editor), Special Projects.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

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.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

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 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.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

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.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

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

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

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

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.

soil aeration

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

tactile

uses touch to communicate

terrestrial

Living on the ground.

vibrations

movements of a hard surface that are produced by animals as signals to others

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

2017. "AnAge Entry for Spermophilus Citellus" (On-line). Human Ageing Genomic Resource. Accessed April 01, 2019 at genomics.senescence.info/species/entry.php?species=Spermophilus_citellus.

Best, T., C. Gerado. 1995. "“Spermophilus Perotensis”" (On-line pdf). JSTOR. Accessed April 01, 2019 at https://www.jstor.org/stable/3504194?seq=1#page_scan_tab_contents.

García-Domínguez, J., E. Priego-Hernández. 2014. "Predation record of a Perote ground squirrel (Xerospermophilus perotensis) by a prairie falcon (Falco mexicanus)" (On-line pdf). De Gruyter. Accessed April 01, 2019 at https://www.degruyter.com/view/j/mamm.2015.79.issue-2/mammalia-2013-0151/mammalia-2013-0151.xml.

García-Domínguez, J., O. Rojas-Soto, J. Galindo-González. 2014. "Present and future potential distribution of the endemic Perote ground squirrel (Xerospermophilus perotensis) under different climate change scenarios" (On-line pdf). De Gruyter. Accessed April 01, 2019 at https://www.degruyter.com/view/j/mamm-ahead-of-print/mammalia-2013-0077/mammalia-2013-0077.xml.

Montero-Bagatella, S., A. González-Romero, G. Sanchez-Rojas, S. Gallina. 2018. "Annual cycle of the Mexican ground squirrel (Xerospermophilus perotensis)" (On-line pdf). Research Gate. Accessed April 01, 2019 at https://www.researchgate.net/publication/325534125_Annual_cycle_of_the_Mexican_ground_squirrel_Xerospermophilus_perotensis.

Ochoa, A., J. Gasca-Pineda, G. Ceballos, L. Equiarte, V. Sánchez-Cordero. 2012. "Spatiotemporal population genetics of the endangered Perote ground squirrel (Xerospermophilus perotensis) in a fragmented landscape" (On-line pdf). JSTOR. Accessed April 01, 2019 at https://www.jstor.org/stable/i23259774.

Valdéz, M., G. Ceballos. 1997. "Conservation of Endemic Mammals of Mexico: The Perote Ground Squirrel (Spermophilus Perotensis)" (On-line pdf). JSTOR. Accessed April 01, 2019 at www.jstor.org/stable/1382640.

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