Cascade golden-mantled ground squirrel
| Cascade golden-mantled ground squirrel | |
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C. saturatus
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| Callospermophilus saturatus (Rhoads, 1895)
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Spermophilus saturatus |
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The Cascade golden-mantled ground squirrel (Spermophilus 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 subgenus 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]
Morphology
Larger in size than its S. madrensis and S. lateralis counterparts, S. saturatus has a vague russet color outlining its head and shoulders and running down the length of its body (at least 286 mm).[2]
Distribution
S. 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] S. saturatus is isolated from its sister species S. lateralis by the Columbia River; their differentiation is likely due to allopatric speciation.[4]
Physiology
At birth, S. 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]
S. 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] S. 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]
Behavior
Examination of alarm calls in response to Canis lupus familiaris among several species of ground squirrels showed that S. 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]
References
- ↑ 1.0 1.1 Linzey, A. V. & Hammerson, G. (2008). Spermophilus saturatus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 8 January 2009.
- ↑ 2.0 2.1 2.2 2.3 2.4 Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 6.0 6.1 6.2 6.3 6.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 7.0 7.1 7.2 7.3 7.4 Lua error in package.lua at line 80: module 'strict' not found.
External links
Media related to Spermophilus saturatus at Wikimedia Commons
