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

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...

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Bibliographic Details
Published in:PloS one 2015-02, Vol.10 (2), p.e0117734-e0117734
Main Authors: McLellan, Michelle L, McLellan, Bruce N
Format: Article
Language:English
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
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Summary: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.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0117734