Urocitellus columbianus

201. Columbian Ground Squirrel Urocitellus columbianus French: Spermophile du Columbia / German: Columbia-Ziesel / Spanish: Ardilla terrestre de Columbia Taxonomy. Arctomys columbianus Ord, 1815, “Between the forks of the Clearwater and Kooskooskie rivers” [Idaho Co., Idaho, USA]. Two subspecies are recognized. Subspecies and Distribution. U.c.columbianusOrd,1815—SEBritishColumbiaandWAlberta(Canada),EWashington,N&CIdaho,andWMontana(USA) U. c. ruficaudus A. H. Howell, 1928 — NE Oregon (USA). Descriptive notes. Head—body mean 258 mm (males) and 247-8 mm (females), tail mean 101-3 mm (males) and 84:3 mm (females); weight mean 490-1 g (males) and 441-4 g (females). The Columbian Ground Squirrel is a large ground squirrel with a plush cinnamon buff dorsal pelage; venter is gray suffused with brown. Neck is light gray and eye ring is a pale buff; sides are light gray or buff. Tail is moderately robust and haired and is dark above and lighter below. Subspecies ruficaudus has a tawnier throat and face with darker legs and feet. Chromosome complement of the Columbian Ground Squirrel is 2n = 32, FN = 60. Habitat. Open grasslands, wet alpine and subalpine mixed forest and forest meadows of the Hudsonian, Canadian, and uppertransition life zones. The Columbian Ground Squirrel is also found on rangelands and agricultural fields. Food and Feeding. The Columbian Ground Squirrel feeds primarily on reproductive tissues of grassland plants (flowers, bulbs, fruits, seeds). Forbs appear to be preferred and are 30-40% higher in digestibility than grasses. It consumes insects and scavenges animal tissue; infanticide and cannibalism have been occasionally reported. Breeding. The Columbian Ground Squirrel inhabits burrows with a vegetation-lined nest chamber in which young are born. Males emerge from hibernation in full reproductive condition, and females enter estrus within a few days of emergence 2-3 weeks later. Breeding continues for c.21 days thereafter. However, females that did not successfully breed can re-enter estrus and breed. Yearling females can forego reproduction due to low body mass. Primary factors influencing age at first reproduction appear to be body mass, environmental conditions, and presence of the mother. Lower reproductive performance in older females is due to senescence. Timing of breeding season varies more at higher elevations. Mean littersizes are 2-1-4-2 in the wild and 3-4-6 in captivity. Litter sizes are negatively correlated with both elevation and latitude. Gestation is 24 days. Young are born hairless and weigh 6-8-11-4 g. Milk composition reflects the need for rapid juvenile growth and is rich in protein and calcium, although low in lipids. Full adult weight is not reached until second year. Young enter hibernation at about 60% of adult mass. Activity patterns. A diurnal squirrel that hibernates for eight months or more and is active less than four months per year. Individuals periodically arouse, depending on ambient temperature, and will initiate aboveground activity under favorable conditions. The Columbian Ground Squirrel can be a nuisance near gardens and is considered a pest around cultivated crops and on some rangelands. Movements, Home range and Social organization. The Columbian Ground Squirrel lives in dense colonies of 24-7-61-7 ind/ha. Home range averages 4200 m? for males and 1000 m* for females. Male home ranges overlap considerably but defended core areas exist around females during breeding season. Adult females are also territorial, which may help protect juveniles from infanticide until emergence. Females establish territories close to their natal burrows. The Columbian Ground Squirrel is highly social and appears to develop social bonds early in life and these continue throughout their adult life. Cross-fostering experiments indicate that social interactions (recognition of kin and agonistic behavior) are based on experience in the nest and therefore are not directly determined by degree of relatedness, as was previously proposed. Prevalence of infanticide is as high as 7-6% of all juveniles and 12-5% of alllitters but is generally not between close relatives. Dispersal between colonies is much higher in males than in females. This appears to be due to a higher level of adult aggression toward young males and a greater acceptance of daughters by adult females. Dispersal distance is usually less than 4 km, but reaches a maximum of 8-5 km. The Columbian Ground Squirrel has a diverse vocal repertoire. Post-copulatory calls appear to function in mate guarding. Alarm calls in response to avian predators are more complex and incorporate a rapid succession of calls than those used for ground predators. Status and Conservation. Classified as Least Concern on The IUCN Red List. Population trend is considered to be stable. Can be considered a local pest and is occasional subject to removal. Its widespread distribution and legally protected nature of some of its habitats suggest that the Columbian Ground Squirrel is not at risk. Bibliography. Bennett (1999a), Broussard, Dobson & Murie (2005), Broussard, Michener et al. (2005), Dobson (1992, 1994, 1995, 2013), Dobson & Oli (2001), Dobson, Risch & Murie (1999), Dobson, Viblanc et al. (2012), Elliot & Flinders (1991), Festa-Bianchet & King (1991), Hare & Murie (1992, 1996), Hubbs et al. (2000), Johnston & Schmitz (1997), King et al. (1991), Manno (2008), Manno et al. (2007), Menkens & Boyce (1993), Neuhaus (2000a, 2000b, 2003, 2006), Neuhaus & Pelletier (2001), Neuhaus, Bennett & Hubbs (1999), Neuhaus, Broussard et al. (2004), Skibiel & Hood (2013), Stevens (1998), Thorington et al. (2012), Towers & Coss (1991), Weddell (1991), Werner et al. (2015).

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