Columbia ground squirrel
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Columbia ground squirrel ( Urocitellus columbianus ) |
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| Urocitellus columbianus | ||||||||||||
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The Columbia ground squirrel ( Urocitellus columbianus , syn .: Spermophilus columbianus ) is a species of squirrel from the genus Urocitellus . It occurs from western Canada to the northwestern United States . The animals live in colonies in meadows, pastures and open tree populations and are very social. Due to their frequent occurrence, they are classified as not endangered and regionally regarded as pasture pests.
features
The Columbia ground squirrel reaches a head-trunk length of about 26 cm, the tail is about 9 cm long and is thus significantly shorter than the rest of the body. The weight is around 440 to 580 grams. The fur of the animals is very dense, they have a strong cinnamon to sand-colored to gray back coloration, the belly is lighter yellow to red-brown. The tail is dark on top and clearly lighter on the underside. The nape of the neck is light gray and there is a sand-colored eye ring around the eyes.
distribution
The Columbia ground squirrel occurs from western Canada to the northwestern United States . In Canada it can be found in the southeast of British Columbia and in the adjacent southwest of Alberta . From there, the distribution area extends south over east Washington , northeast Oregon , most of northern and central Idaho and western Montana .
Way of life
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The Columbia ground squirrel is diurnal and lives mainly in open areas, mainly in meadows and pastures at medium altitudes, sometimes also in areas with open trees. The species also occurs frequently in wet meadows, which can occasionally be flooded, as well as in agricultural areas and pastures.
The Columbia ground squirrel is primarily herbivorous and, like other ground squirrels, its diet consists primarily of various parts of plants such as grass, leaves, flowers and fruits, as well as seeds of the plants that occur. In addition, there are small amounts of animal food, mainly insects, small rodents and dead fish. The animals can also climb to get to plant material in bushes and trees. The animals hibernate in hibernation , which usually lasts about 8.5 months, depending on the temperature, the animals wake up during this time. The time of awakening and the subsequent mating depends on the altitude and the outside temperature and accordingly varies regionally. The species population ranges from an average of 16.2 individuals per acre in natural habitats in northwest Alberta to 61.7 individuals per acre in agricultural areas in Washington, with juvenile densities ranging from 4.6 to 20.7 individuals per acre .
The animals live like other ground squirrels on the ground and in complex underground burrows. The burrows that are used for rearing young and for hibernation usually have several chambers and entrances and penetrate the ground to a depth of about one meter. The animals also dig short and shallow escape burrows. The Columbia ground squirrel lives in colonies made up of an adult male and several females with their respective juveniles. He is very social and within the social fabric there are very strong bonds between the individual animals. The territories of the males cover an average of 4200 m 2 , those of the females only 1000 m 2 . The territories of the males overlap with each other, with the males mainly defending the core areas and the areas of reproductive females against other males. The aggressiveness is particularly high during the breeding season and then decreases significantly. Females are also territorial and protect their offspring until they leave the burrows. The females in particular often stay close to their birth structures, which means that there is a high degree of kinship and the rate of inbreeding with the respective fathers is increased. Infanticide by other animals in the colony was documented, with 7.6 percent of all young animals being killed in 12.5 percent of all litters by conspecifics, usually no close relatives, over a period of two years. Since the animals move frequently from one colony to a neighboring one, there is a correspondingly higher level of aggressiveness, which is also directed against the offspring of other males and females in the colony, whereby male offspring in particular are affected. The spread of the animals after leaving their own colony is usually moderate and is on average at a distance of 4 kilometers, a maximum of 8.5 kilometers from the original burrow. New colonies are seldom created; the probability of a new colony emerging increases with the distance between existing burrows. Overall, the genetic distance between animals in a population is very small, so the degree of relationship within larger regions is very high. The animals sometimes maintain close physical contact with one another, they greet each other and play with one another. Communication occurs through a wider range of sounds than related species. Like other ground squirrels, the animals emit specific alarm calls in which they can also express the type of danger. In addition, there are specific sounds for the pairing, which are answered by the respective partner.
The mating season begins a few days after the females wake up in spring. The males are able to reproduce when they wake up. Females who were not mated in the following 21 days or are not pregnant after this period of time will ovulate again and mate accordingly. The young are born in the underground nest after a gestation period of around 24 days. The litter consists of two to a maximum of seven, but usually between two and five, young animals. At higher altitudes and in more northerly regions the number of young animals decreases. The young animals have a weight of 6.8 to 11.4 grams at birth and are hairless. By the time they first hibernate, they reach around 60 percent of the weight of the adult animals, and they usually only reach their full weight in the second year of life. Young females born in the previous year, however, often do not have their first litter until they are two years old, depending on their weight after awakening and the weather conditions.
The mortality of the animals can be very high regionally and in years with heavy frost and snowfall, whereby the young animals usually have a lower death rate than adult animals, but otherwise the probability of survival increases with weight. However, there is above all a correlation with the survival time of the dams after weaning, and the survival rate also decreases after warmer summers and with high population densities of the animals and lower food availability. Through feeding experiments, both the lifespan and the number of young animals could be significantly increased, with the digestibility and thus the availability of the food playing a role and less the pure quantity. Among adult males, the death rate is particularly high during the mating season, and females are more likely to die raising young than losing their litter. As predators various predators and birds of prey are documented, added snakes like the Western Rattlesnake ( Crotalus viridis ) and the pine snake ( Pituophis melanoleucus ). Among the parasites, ectoparasites such as various fleas , animal lice , mites and one type of tick are documented, and there are also endoparasites such as various Eimeria species and a Trypanosoma species. The influence of the parasites on the animals could be demonstrated experimentally by removing the ectoparasites; Correspondingly treated females were in better physical condition when rearing their young and had on average more young than parasite-infested females. The species is also a potential carrier of plague pathogens ( Yersinia pestis ) and Rocky Mountain spotted fever .
Systematics
The Columbia ground squirrel is classified as an independent species within the genus Urocitellus , which consists of twelve species. The species has long been classified as part of the ground squirrel and within the subgenus Spermophilus . After a comprehensive molecular biological investigation, the Columbia ground squirrel was assigned to the now independent genus Urocitellus together with several other species . The first scientific description comes from the American zoologist George Ord from 1815. He created it on the basis of individuals from the region between the forks of the Clearwater River and the Kooskooskie River in Idaho County , Idaho, and described the Columbia ground squirrel under the name Spermophilus columbianus .
Within the species, together with the nominate form, two subspecies are distinguished:
- Urocitellus columbianus columbianus : nominate form, occurs in most of the range with the exception of northeastern Oregon.
- Urocitellus columbianus ruficaudus : This subspecies lives in northeastern Oregon. It differs from the nominate form in that it has a tan throat and face, darker legs and feet, and a wider skull.
Status, threat and protection
The Columbia ground squirrel is classified as Least Concern (LC) by the International Union for Conservation of Nature and Natural Resources (IUCN). This is justified by the comparatively large distribution area, the assumed frequent occurrence and the lack of risks that could endanger the existence of the plant. Potential threats are not known, regionally it is regarded as a pest.
supporting documents
- ↑ a b c d e f g h i j k l m Richard W. Thorington Jr. , John L. Koprowski, Michael A. Steele: Squirrels of the World. Johns Hopkins University Press, Baltimore MD 2012, ISBN 978-1-4214-0469-1 , pp. 355-357 .
- ↑ a b c d e f Urocitellus columbianus in the Red List of Threatened Species of the IUCN 2016.1. Posted by: AV Linzey, NatureServe (G. Hammerson), 2008. Retrieved August 29, 2016.
- ↑ Matthew D. Herron, Todd A. Castoe, Christopher L. Parkinson: Sciurid phylogeny and the paraphyly of holarctic ground squirrels (Spermophilus). Molecular Phylogenetics and Evolution 31, 2004; Pp. 1015-1030. ( Full text , PMID 15120398 )
- ↑ Kristofer M. Helgen, F. Russell Cole, Lauren E. Helgen, Don E. Wilson: Generic Revision in the holarctic ground squirrels genus Spermophilus. Journal of Mammalogy 90 (2), 2009; Pp. 270-305. doi : 10.1644 / 07-MAMM-A-309.1
- ^ Charles L. Elliott, Jerran T. Flinders: Spermophilus columbianus. Mammalian Species 372, 1991; Pp. 1-9. ( Full text ( Memento of the original from February 20, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. )
- ↑ a b Spermophilus columbianus . In: Don E. Wilson , DeeAnn M. Reeder (Eds.): Mammal Species of the World. A taxonomic and geographic Reference. 2 volumes. 3. Edition. Johns Hopkins University Press, Baltimore MD 2005, ISBN 0-8018-8221-4 .
literature
- Richard W. Thorington Jr. , John L. Koprowski, Michael A. Steele: Squirrels of the World. Johns Hopkins University Press, Baltimore MD 2012, ISBN 978-1-4214-0469-1 , pp. 355-357 .
- Charles L. Elliott, Jerran T. Flinders: Spermophilus columbianus. Mammalian Species 372, 1991; Pp. 1-9. ( Full text )
Web links
- Urocitellus columbianus inthe IUCN Red List of Threatened Species 2016.1. Posted by: AV Linzey, NatureServe (G. Hammerson), 2008. Retrieved August 29, 2016.