Overview

Distribution

Spermophilus annulatus is endemic to west-central Mexico.

Biogeographic Regions: nearctic ; neotropical

  • Nowak, R. 1991. Walker's Mammals of the World. Baltimore: The Johns Hopkins University Press.
  • Wilson, D., D. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. Washington: Smithsonian Institution Press.
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Range Description

This species occurs from Nayarit south to northern Guerrero, Mexico (Thorington and Hoffmann 2005). It occurs at elevations from sea level to 1,200 m (Best 1995).
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Physical Description

Morphology

The coloration of ring-tailed ground squirrels varies seasonally; these squirrels are more brightly colored during the breeding season. The head is predominantly black, while the body is a mix of black, buff, and pinkish coloration. Total length varies from 383 to 470 mm. The tail is narrow and has approximately fifteen annulations, or stripes. It is not as bushy as the tails of other squirrel species and is as long as the head and body of the animal. The skulls of females are generally larger than those of males.

Range length: 383 to 470 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

  • Murie, J., G. Michener. 1984. The Biology of Ground-Dwelling Squirrels. Nebraska: University of Nebraska Press.
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Ecology

Habitat

Ring-tailed ground squirrels inhabit the tropical lowlands of western Mexico. They are found in dense tropical forests and palm groves, especially in areas with thick, vine growth on larger trees. Spermophilus annulatus create burrows and cavities under cover of thick vegetation, on hillsides and near cultivated areas. These squirrels have been known to live in the walls of barns.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest

Other Habitat Features: agricultural

  • Best, T. 1995. Mammalian Species, 508. New York: American Society of Mammalogists.
  • Black, C. 1972. Holarctic evolution and dispersal of squirrels. Evolutionary Biology, 6: 205-322.
  • Prakash, L., P. Gosh . 1975. Rodents in Desert Environments. The Netherlands: Dr. W. Junk b.v. Publishers.
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Habitat and Ecology

Habitat and Ecology
This squirrel inhabits dense, tropical, deciduous forests, and is common in plains. Its burrows are on hillsides among rocks, and in sandy flats along walls and hedges bordering cultivated fields. It also occurs in the shade of the dense groves of oil palms (Arecaceae), with its burrows under masses of fallen palm fronds or sheltered by the thorny growth of mesquite (Prosopis) and catclaw (Acacia).

This squirrel eats fruits and nuts, and sometimes it also may feed on insects. Breeding occurs during the dry season (December to June). A female captured in February had four embryos (Best 1995).

Systems
  • Terrestrial
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Trophic Strategy

Spermophilus annulatus eats fruits and nuts and may also consume insects. Oil palm, mesquite, and cactus seeds are eaten, as well as the fleshy fronds of Opuntia cactus, figs, and other wild fruits and seeds. In agricultural areas they eat corn and the seeds of other agricultural plants. They can climb to the ends of branches in search of fruits and seed pods and will dig for seeds as well.

Animal Foods: insects

Plant Foods: seeds, grains, and nuts; fruit

Primary Diet: herbivore (Frugivore , Granivore )

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Associations

Although ecosystem roles of S. annulatus have not been described in detail, they impact plant regeneration through their seed predation and may help to disperse the seeds of some plants. They may also act as an important prey base for birds of prey and other predators.

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Predation on S. annulatus has not been described but it is likely that they are taken by a variety of small to medium-sized predators, especially birds of prey. They are agile, vigilant, and seek refuge in burrows and cavities to avoid predation.

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Known prey organisms

Spermophilus annulatus preys on:
Insecta

This list may not be complete but is based on published studies.
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Life History and Behavior

Behavior

Communication has not been studied in S. annulatus. However, Spermophilus species in general communicate with sounds, body language, by way of smells, and by touch, as do most mammals. Ground squirrels are known for the range of vocalizations they use, from whistles and chatters to trills and buzzes. S. annulatus is known to emit shrill whistling noises when alarmed. Specific warning vocalizations that distinguish between terrestrial and avian predators are known in other Spermophilus species. Some species have been recorded "kissing" when they meet and using scent marking. Ground squirrels perceive their environment using this same suite of senses.

Communication Channels: visual ; tactile ; acoustic ; chemical

Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical

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Life Expectancy

The lifespan of S. annulatus is not known. Other Spermophilus species live for a maximum of 11 years (S. beldingi), but typically for about 3 to 4 years in males and 4 to 6 years in females. The higher male mortality is a result of the risks associated with male-biased dispersal.

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Reproduction

The mating system of S. annulatus has not been described. In other Spermophilus species, males compete for access to females as they emerge from hibernation in the spring.

The breeding season of S. annulatus is in the dry season (December to June). Little has been published on the reproduction of this species, however other species in the genus Spermophilus breed once yearly, have a gestation period of approximately 30 days, and have 3 to 6 young in a litter.

Breeding interval: Breeding occurs once yearly.

Breeding season: Breeding occurs from December through June.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

Parental care has not been studied in S. annulatus. As in all mammals, females nurse and care for their young until they reach independence. In other Spermophilus species, the young are born helpless, are cared for in a nest chamber, and are weaned in the first 1 to 2 months of life. They begin making excursions from the burrow around the time of weaning. Typically male young disperse at independence but female young remain in their natal area.

Parental Investment: altricial ; female parental care

  • Best, T. 1995. Mammalian Species, 508. New York: American Society of Mammalogists.
  • Murie, J., G. Michener. 1984. The Biology of Ground-Dwelling Squirrels. Nebraska: University of Nebraska Press.
  • Prakash, L., P. Gosh . 1975. Rodents in Desert Environments. The Netherlands: Dr. W. Junk b.v. Publishers.
  • Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Washington: Smithsonian Institution Press.
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Conservation

Conservation Status

This species has a global conservation heritage status of G4 that indicates that S. annulatus is uncommon but not rare. Although population numbers are decreasing, they are not considered in danger of extinction.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Álvarez-Castañeda, S.T., Castro-Arellano, I., Lacher, T. & Vázquez, E.

Reviewer/s
McKnight, M. (Global Mammal Assessment Team) & Amori, G. (Small Nonvolant Mammal Red List Authority)

Contributor/s

Justification
This species is listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.
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Population

Population
This species is common in suitable habitats (Best 1995).

Population Trend
Unknown
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Threats

Major Threats
No major threats are known to this species.
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Management

Conservation Actions

Conservation Actions
A number of protected areas occur within its range.
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Relevance to Humans and Ecosystems

Benefits

Much of the natural habitat of these ground squirrels is being cleared for agricultural purposes. They are considered agricultural pests in some areas because they eat fruit from orchards, corn, and other crops.

Negative Impacts: crop pest

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It is not known what, if any, benefits this species provides to humans. They may act to disperse the seeds of some wild, native plants.

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Wikipedia

Ring-tailed ground squirrel

The ring-tailed ground squirrel (Notocitellus annulatus) is a species of rodent in the Sciuridae family. It is endemic to the Pacific coast region of central Mexico.[2] It is a common species and feeds mainly on fruits and nuts, and the IUCN has assessed it as being of "least concern".

Description[edit]

The ring-tailed ground squirrel is between 383 and 470 mm (15 and 19 in) long, half of this being the tail. Compared to the California ground squirrel (Otospermophilus beecheyi) it is slightly smaller, has more slender legs and broader, less-pointed ears. The incisors are orange and the large cheek pouches open inside the mouth. The crown of the head and upper parts of the body have mixed blackish-brown and buff hairs and the chin, throat and underparts are buff. The tail is slender and not bushy, the colour being mixed buff and black above and brownish beneath, with about fifteen dark rings.[3]

Distribution and habitat[edit]

The ring-tailed ground squirrel is endemic to western Mexico, its range extending from the State of Nayarit to the State of Guerrero. It is a lowland species, ranging up to elevations of about 1,200 metres (3,900 ft). It occupies a range of habitat types. It may occur in deciduous forests of vine-clad trees or on more open slopes among rocks. It also inhabits the borders of cultivated fields, and oil palm (Elaeis guineensis) plantations where the ground is littered with fallen palm fronds and mesquite scrub. Its burrows are often in walls or dykes, or hidden under spreading cacti or scrub. It sometimes inhabits holes in trees.[3]

Behaviour[edit]

The ring-tailed ground squirrel eats corn and other seeds but mainly feeds on fruit and nuts. These include oil palm seeds, wild figs, mesquite seeds and the fleshy fruits of prickly pears (Opuntia). It may also consume insects. It mostly moves about on the ground, scurrying from one piece of cover to another, sometimes pausing to dig up some morsel or sit on its haunches to eat, holding the food in its forepaws. It sometimes climbs a few metres up a small tree and gathers food from low branches. When startled it may rush a short way up a tree, peer at the intruder, retire round the back of the trunk and descend to the ground, running away under cover to the nearest burrow. If startled in the open it may freeze, or may run direct to a burrow, often stopping at the entrance to utter a short whistle or emit chirping notes. When moving about, it sometimes stops and stands upright on its hind feet, propping itself up with its tail. When it runs, it carries its tail in a curve, and is altogether more dainty and agile than most ground squirrels.[3]

Breeding takes place in the dry season between December and June and one female that was examined was carrying a litter of four embryos.[3]

Status[edit]

The ring-tailed ground squirrel is common in suitable locations within its range. The International Union for Conservation of Nature has identified no particular threats and has assessed its conservation status as being of "least concern".[1]

References[edit]

  1. ^ a b Álvarez-Castañeda, S. T.; Castro-Arellano, I.; Lacher, T.; Vázquez, E. (2008). Spermophilus annulatus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 5 December 2014.
  2. ^ Helgen, Kristofer M.; Cole, F. Russel; Helgen, Lauren E.; and Wilson, Don E (2009). "Generic Revision in the Holarctic Ground Squirrel Genus Spermophilus". Journal of Mammalogy 90 (2): 270–305. doi:10.1644/07-MAMM-A-309.1. Archived from the original on 22 October 2011. 
  3. ^ a b c d Best, Troy L. (1995). "Spermophilus annulatus". Mammalian Species 508: 1–4. JSTOR 3504104. 
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