Cascade golden-mantled ground squirrel

Cascade golden-mantled ground squirrel
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Sciuridae
Genus:	Callospermophilus
Species:	C. saturatus
Binomial name
Callospermophilus saturatus (Rhoads, 1895)
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]

• Media related to Spermophilus saturatus at Wikimedia Commons