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1 February 2009 Darkness, Twilight, and Daylight Foraging Success of Bears (Ursus americanus) on Salmon in Coastal British Columbia
D. R. Klinka, T. E. Reimchen
Author Affiliations +
Abstract

We examine foraging behavior of coastal black bears (Ursus americanus kermodei) during different light regimes on a salmon stream in British Columbia, Canada (2000–2002). Bears (maximum 7 simultaneously) were primarily active during daylight near the onset of the salmon spawning run and shifted to twilight and darkness as the spawning run progressed. Overall time budget included search and pursuit (58%), handling and ingestion (38%), and agonistic interactions with other bears (4%). Scavenging was greatest during daylight (19%) and lowest during darkness (3%). Bears were most efficient at capturing live salmon when standing (35.4% success) followed by running (20.5%) and walking (15.2%). Highest capture efficiency occurred during twilight (33.6%) compared with daylight (26.5%) and darkness (24.7%). Capture rate ranged from 1 to 3 salmon per hour per bear. Our results suggest that bears increased their total salmon intake by alternate use of visual and auditory cues during daylight and darkness.

D. R. Klinka and T. E. Reimchen "Darkness, Twilight, and Daylight Foraging Success of Bears (Ursus americanus) on Salmon in Coastal British Columbia," Journal of Mammalogy 90(1), 144-149, (1 February 2009). https://doi.org/10.1644/07-MAMM-A-200.1
Accepted: 1 June 2008; Published: 1 February 2009
KEYWORDS
darkness
foraging efficiency
Oncorhynchus
sensory modes
twilight
Ursus
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