Small endotherms typically have elevated and relatively invariant rates of metabolism, but adaptations such as food hoarding and hibernation endow some species with considerable energetic flexibility in responding to resource fluctuations. I examined the interactions between resource availability, food hoarding, and hibernation in a population of eastern chipmunks (Tamias striatus) subjected to seasonal and multi-annual periods of resource shortage. Incompatibility of torpor and digestion could be an important constraint associated with relying on stored food rather than body fat during hibernation, but documentation of torpor patterns and digestive efficiency of captive chipmunks revealed that digestion is actually enhanced by torpor expression. Measures of energy expenditure and food delivery by free-ranging chipmunks in autumn revealed that food hoarding also permitted rapid accumulation of large energy reserves before thermoregulatory constraints necessitated termination of above-ground activity. Thus, a combination of food hoarding and hibernation permits rapid energy accumulation when resources are abundant and effective energy conservation when resources are scarce. Despite this, chipmunks responded to experimental increases of autumn hoard size by substantially reducing winter torpor expression, suggesting that much of the resource accumulation permitted by larder hoarding is allocated to maintaining elevated rates of metabolism in the winter hibernaculum. This pattern of allocation suggests torpor expression is associated with important costs and contradicts a major paradigm of hibernation research by demonstrating that low levels of torpor expression can reflect an absence of energetic necessity rather than a lack of physiological capability. In an ecological context, the capacity of chipmunks to vary expenditure according to resource abundance represents a potent decoupling mechanism in consumer-resource interactions. Energetic flexibility of this form
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.38068 |
| Date | January 2001 |
| Creators | Humphries, Murray M. |
| Contributors | Kramer, D. L. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001845284, proquestno: NQ75643, Theses scanned by UMI/ProQuest. |
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