title: Physiological and behavioral adaptations in bats living at high latitudes.
abstract: Widespread animals at the extremes of the species' distribution experience ecological constraints different than individuals in the core of the distribution. For example, small endotherms at very high latitudes face short summers with cool temperatures and a lack of true darkness. In particular, insectivorous bats at high latitudes may experience constraints because of their unique life history traits, and may have different energy requirements than bats at lower latitudes. To evaluate the extent of these differences, we estimated an energy budget and refueling rates for reproductively active female little brown bats (Myotis lucifugus) roosting in buildings in eastern Alaska (~63°N). Physiological parameters (torpor use and metabolic rates) and daily energy expenditures (25.7±5.3kJd(-1)) were similar to, or slightly lower than, conspecifics at lower latitudes. Northern little brown bats foraged for less time than southerly conspecifics, but measurements of plasma β-hydroxybutyrate concentrations suggest that northern bats refuel at a rate considerably higher than those to the south. It appears that high refueling rates (and therefore foraging intensity) involve a dietary shift to orb-weaver spiders, which are abundant and likely offer higher energetic benefit than the small, flying insects consumed by individuals in other parts of the distribution. Environmental factors may limit species' distributions, but our results provide an example of a population at the limit of their geographic range that has compensated for environmental challenges by adopting unique behavioral strategies while the underlying physiology (including daily energy expenditure) remains similar to populations at the core of the species' range.
authors.affiliation: Cooperative Wildlife Research Laboratory, Department of Zoology, Southern Illinois University, Carbondale, United States. Electronic address: jgboyles@siu.edu.
authors.forename: Justin G
authors.initials: JG
authors.lastname: Boyles
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, United States.
authors.forename: Liam P
authors.initials: LP
authors.lastname: McGuire
authors.affiliation: Cooperative Wildlife Research Laboratory, Department of Zoology, Southern Illinois University, Carbondale, United States.
authors.forename: Esmarie
authors.initials: E
authors.lastname: Boyles
authors.affiliation: Alaska Center for Conservation Science, University of Alaska Anchorage, United Sates.
authors.forename: Jesika P
authors.initials: JP
authors.lastname: Reimer
authors.affiliation: Cooperative Wildlife Research Laboratory, Department of Zoology, Southern Illinois University, Carbondale, United States.
authors.forename: Christopher A C
authors.initials: CA
authors.lastname: Brooks
authors.affiliation: 61.5 Tok Cutoff, Slana, Alaska, United States.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Rutherford
authors.affiliation: 61.5 Tok Cutoff, Slana, Alaska, United States.
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Rutherford
authors.affiliation: Department of Biology, Indiana State University, Terre Haute, United States.
authors.forename: John O
authors.initials: JO
authors.lastname: Whitaker
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, United States.
authors.forename: Gary F
authors.initials: GF
authors.lastname: McCracken
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000097:blood; D000222:Adaptation, Physiological / Q000502:physiology*; D000531:Altitude; D000818:Animals; D002685:Chiroptera / Q000097:blood / Q000502:physiology*; D004435:Eating / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D012016:Reference Values; D012621:Seasons; D012881:Skin Temperature; D064348:Torpor / Q000502:physiology
chemical_list: D020155:3-Hydroxybutyric Acid
keywords: Energy budgets; Foraging intensity; Heterothermy; Myotis; Plasma metabolites; Torpor; β-hydroxybutyrate