Effect of season and high ambient temperature on activity levels and patterns of grizzly bears (Ursus arctos)

• Published in: PloS one Vol. 10; no. 2; p. e0117734
• Main Authors: McLellan, Michelle L, McLellan, Bruce N
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.02.2015; Public Library of Science (PLoS)
• Subjects: Activity patterns; Ambient temperature; Animal behavior; Animal populations; Animals; Axis movements; Behavior, Animal - physiology; Berries; Circadian Rhythm; Climate Change; Coasts; Collars; Conservation; Ecosystems; Energy; Environmental protection; Female; Food; Foraging behavior; Fruits; Global Positioning System; Grizzly bear; Grizzly bears; Heat; Male; Maximum temperatures; Motion sensors; Mountains; Precipitation; Predation; Seasons; Sensors; Summer; Switches; Temperature; Temperature effects; Ursidae - physiology; Ursus arctos; British Columbia Canada; Canada
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0117734

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.