title: Effect of season and high ambient temperature on activity levels and patterns of grizzly bears (Ursus arctos).
abstract: Understanding factors that influence daily and annual activity patterns of a species provides insights to challenges facing individuals, particularly when climate shifts, and thus is important in conservation. Using GPS collars with dual-axis motion sensors that recorded the number of switches every 5 minutes we tested the hypotheses: 1. Grizzly bears (Ursus arctos) increase daily activity levels and active bout lengths when they forage on berries, the major high-energy food in this ecosystem, and 2. Grizzly bears become less active and more nocturnal when ambient temperature exceeds 20°C. We found support for hypothesis 1 with both male and female bears being active from 0.7 to 2.8 h longer in the berry season than in other seasons. Our prediction under hypothesis 2 was not supported. When bears foraged on berries on a dry, open mountainside, there was no relationship between daily maximum temperature (which varied from 20.4 to 40.1°C) and the total amount of time bears were active, and no difference in activity levels during day or night between warm (20.4-27.3°C) and hot (27.9-40.1°C) days. Our results highlight the strong influence that food acquisition has on activity levels and patterns of grizzly bears and is a challenge to the heat dissipation limitation theory.
authors.affiliation: South Coast Grizzly Bear Project, Nelson, British Columbia, Canada.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: McLellan
authors.affiliation: British Columbia Fish, Wildlife and Habitat Management, D'Arcy, British Columbia, Canada.
authors.forename: Bruce N
authors.initials: BN
authors.lastname: McLellan
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002940:Circadian Rhythm; D057231:Climate Change; D005260:Female; D008297:Male; D012621:Seasons; D013696:Temperature; D001503:Ursidae / Q000502:physiology