Adaptive coat colour polymorphism in the Kermode bear of coastal British Columbia

We investigated potential ecological attributes of the striking coat colour polymorphism in the black bear ( Ursus americanus kermodei Hornaday) occurring on several small islands off the mid-coast of British Columbia, where a white morph (Kermode), fully recessive to the black morph, reaches 10–25% of the population. During three autumn field seasons (2000–2002; 697 h of observation time), we monitored salmon capture behaviour of individual bears (black, N  = 37; white, N  = 4). Both colour morphs foraged on salmon throughout daylight and darkness but with twice the rate during darkness. Log-linear analysis of capture efficiency (success/attempts) and average capture success per bout of the white morph was marginally lower than the black morph during darkness (22.8%, N  = 158 versus 25.8%, N  = 279 respectively; P  < 0.04), although it was significantly higher during daylight (34.1%, N  = 132 versus 25.3%, N  = 896, respectively, P  < 0.02), with similar trends in three different pursuit modes. Replicated ( N  = 10–14) field experiments involving a colour dimorphic simulated predator (i.e. human in a black or white cloak) showed that salmon were one-half as evasive during darkness than during daylight, with no differences ( P  > 0.4) in response to either the white or black models; however, during daylight, salmon were twice as evasive to the black compared to the white model ( P  < 0.001). The persistence of this coat colour polymorphism may be facilitated by increased salmon accessibility to the Kermode bear and diel foraging differences between morphs. These results are consistent with multi-niche models of adaptive variability.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 479–488.