title: Towards an energetic landscape: broad-scale accelerometry in woodland caribou.
abstract: Energetic balance is a central driver of individual survival and population change, yet estimating energetic costs in free- and wide-ranging animals presents a significant challenge. Animal-borne activity monitors (using accelerometer technology) present a promising method of meeting this challenge and open new avenues for exploring energetics in natural settings. To determine the behaviours and estimated energetic costs associated with a given activity level, three captive reindeer (Rangifer tarandus tarandus) at the Toronto Zoo were fitted with collars and observed for 53 h. Activity patterns were then measured over 13 months for 131 free-ranging woodland caribou (R. t. caribou) spanning 450,000 km(2) in northern Ontario. The captive study revealed a positive but decelerating relationship between activity level and energetic costs inferred from previous behavioural studies. Field-based measures of activity were modelled against individual displacement, vegetation abundance (Normalized Difference Vegetation Index), snow depth and temperature, and the best fit model included all parameters and explained over half of the variation in the data. Individual displacement was positively related to activity levels, suggesting that broad differences in energetic demands are influenced by variation in movement rates. After accounting for displacement, activity was highest at intermediate levels of vegetation abundance, presumably due to foraging behaviour. Snow depth, probably associated with digging for winter forage, moderately increased activity. Activity levels increased significantly at the coldest winter temperatures, suggesting the use of behavioural thermoregulation by caribou. These interpretations of proximate causal factors should be regarded as hypotheses subject to validation under normal field conditions. These results illustrate the landscape characteristics that increase energetic demands for caribou and confirm the great potential for the use of accelerometry in studies of animal energetics.
authors.affiliation: Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada.|University of Minnesota, Biology Program, 123 Snyder Hall, 1475 Gortner Ave., St. Paul, MN 55108, USA.
authors.forename: Anna A
authors.initials: AA
authors.lastname: Mosser
authors.affiliation: Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada.
authors.forename: Tal
authors.initials: T
authors.lastname: Avgar
authors.affiliation: Ontario Terrestrial Assessment Program, Ontario Ministry of Natural Resources, 1235 Queen Street East, Sault Ste. Marie, ON, P6A 2E5, Canada.
authors.forename: Glen S
authors.initials: GS
authors.lastname: Brown
authors.affiliation: Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada.
authors.forename: C Spencer
authors.initials: CS
authors.lastname: Walker
authors.affiliation: Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada.
authors.forename: John M
authors.initials: JM
authors.lastname: Fryxell
mesh_terms: D061725:Accelerometry / Q000662:veterinary; D000818:Animals; D005260:Female; D009068:Movement; D009864:Ontario; D012053:Reindeer / Q000502:physiology*; D012621:Seasons
keywords: Rangifer; accelerometry; biotelemetry; energetics; landscape