Cascade golden-mantled ground squirrel | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Rodentia |
Family: | Sciuridae |
Genus: | Callospermophilus |
Species: | C. saturatus
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Binomial name | |
Callospermophilus saturatus (
Rhoads, 1895)
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Synonyms | |
Spermophilus saturatus |
The Cascade golden-mantled ground squirrel (Callospermophilus saturatus) is a species of rodent in the family Sciuridae, in the order Rodentia. [2] It is the largest species of the three within the genus Callospermophilus. [2] It is found in the Cascade Mountains in the province of British Columbia, Canada and the state of Washington, United States. [1] [3]
Larger in size than its C. madrensis and C. lateralis counterparts, C. saturatus has a vague russet color outlining its head and shoulders and running down the length of its body (at least 286 mm). [2]
C. saturatus occurs in the northwestern United States, north of the Columbia River, south of the Tulameen River in British Columbia, and west of the Similkameen River. [2] No fossils have yet been found. [2] C. saturatus is isolated from its sister species S. lateralis by the Columbia River; their differentiation is likely due to allopatric speciation. [4]
At birth, C. saturatus are ectothermic. [5] Development of endothermy occurs gradually as individuals grow, increasing both body mass and amount of body fur. [5] Individuals removed from their mother at 6 days of age lost body temperature at a faster rate than at 36 days, when individuals were able to maintain a high internal body temperature and determined to be homeothermic. [5] This 36-day mark is conveniently the age at which offspring leave their burrows. [5] Individuals remained homeothermic in response to a 2-day removal of food and water at 2-week intervals. [5] Even with this drastically reduced body mass, torpor was not induced. [5] Smaller individuals did become hypothermic, however, and were returned to the mother to be re-warmed. [5]
Daily energy expenditures showed a small but significant increase of 10% as litter size increased, across a range of 3 to 5 offspring, the norm for the species. [6] Body mass, time spent above ground and time spent foraging were not correlated. [6] For the large amount energy contained in the mother's milk, changes in metabolism were small. [6] Body mass and age of offspring was independent of litter size. [6] The fact that daily energy expenditure does not vary with litter size suggests that other factors, such as habitat quality, affect number of offspring. [6]
C. saturatus have been noted to move in two distinct ways – walking (mean speed of .21 m/s) and running (mean speed of 3.63 m/s). [7] 26.9% of total time spent daily above ground was spent walking, while only 3.6% was spent running. [7] It is noted that individuals run at their maximum aerobic speed of 3.6 m/s instead of the more maintainable minimum running pace of 2 m/s in order to minimize predation. [7] C. saturatus moved an average of 5 km/day – 1.5 km walking and 3.3 km running. [7] This considerable distance required 28.75 kJ/day of net added energy cost to do so, a 29% increase above BMR and 13% of daily energy expenditure. [7]
Examination of alarm calls in response to Canis lupus familiaris among several species of ground squirrels showed that C. saturatus have a dialect of their own. [4] Vocalizations were distinct, and could be identified 100% of the time by a discriminant source. [4] This suggests that vocalizations can be used in addition to genetics and morphology to differentiate and designate species. [4]