title: Phenological variation in annual timing of hibernation and breeding in nearby populations of Arctic ground squirrels.
abstract: Ecologists need an empirical understanding of physiological and behavioural adjustments that animals can make in response to seasonal and long-term variations in environmental conditions. Because many species experience trade-offs between timing and duration of one seasonal event versus another and because interacting species may also shift phenologies at different rates, it is possible that, in aggregate, phenological shifts could result in mismatches that disrupt ecological communities. We investigated the timing of seasonal events over 14 years in two Arctic ground squirrel populations living 20 km apart in Northern Alaska. At Atigun River, snow melt occurred 27 days earlier and snow cover began 17 days later than at Toolik Lake. This spatial differential was reflected in significant variation in the timing of most seasonal events in ground squirrels living at the two sites. Although reproductive males ended seasonal torpor on the same date at both sites, Atigun males emerged from hibernation 9 days earlier and entered hibernation 5 days later than Toolik males. Atigun females emerged and bred 13 days earlier and entered hibernation 9 days earlier than those at Toolik. We propose that this variation in phenology over a small spatial scale is likely generated by plasticity of physiological mechanisms that may also provide individuals the ability to respond to variation in environmental conditions over time.
authors.affiliation: Institute of Arctic Biology, University of Alaska, Fairbanks, 902 North Koyukuk Drive, Fairbanks, AK 99775, USA. gjvermeij@ucdavis.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sheriff
authors.forename: G Jim
authors.initials: GJ
authors.lastname: Kenagy
authors.forename: Melanie
authors.initials: M
authors.lastname: Richter
authors.forename: Trixie
authors.initials: T
authors.lastname: Lee
authors.forename: Øivind
authors.initials: Ø
authors.lastname: Tøien
authors.forename: Franziska
authors.initials: F
authors.lastname: Kohl
authors.forename: C Loren
authors.initials: CL
authors.lastname: Buck
authors.forename: Brian M
authors.initials: BM
authors.lastname: Barnes
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000413:Alaska; D000704:Analysis of Variance; D000818:Animals; D002980:Climate; D005260:Female; D006605:Hibernation / Q000502:physiology*; D008297:Male; D012589:Sciuridae / Q000502:physiology*; D012621:Seasons; D012737:Sex Factors; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013045:Species Specificity; D018709:Statistics, Nonparametric; D013997:Time Factors