Sensory modes, foraging profitability, colour polymorphism and behavioural plasticity in coastal bear populations Daniel Robert Klinka B.Sc., University of Victoria, 1998 A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE In the department of Biology O Daniel Robert Klinka, 2004 University of Victoria All rights reserved. This thesis may not be reproduced in whole or in part, by photocopy or other means, without the permission of the author Supervisor: Dr. T.E. Reimchen Abstract Mammalian carnivores can augment their temporal foraging niche by shifting to alternate sensory modes, and this can result in greater phenotypic and behavioural variability. Temporal shifts in activity patterns provide an opportunity to investigate changes in foraging strategies in species that exhibit such behavioural and phenotypic variability. To this end, I compared the diurnal and nocturnal foraging of two colour morphs of a polymorphic subspecies of black bear (Ursus americanus kermodei) on a salmon stream in British Columbia. I found that bears (Nwhite=4,Nslack=37) adjusted fishing behaviour according to light level and salmon abundance, and foraging efficiency varied between colour morphs and light level. Salmon were significantly more active but less timid during darkness, and were most timid towards the black morph during daylight which may have accounted for the significant differences in foraging efficiencies between morphs among light levels. Isotope analysis of hair segments obtained from a large scale sampling regime indicated dietary divergence between morphs among seasons and localities. White bears incorporated more marine derived nutrients into their diets than black morphs in many localities. Overall, both morphs were similar during non-foraging behaviours and social interactions among light levels. Bears spent 38% of observed time feeding which remained relatively consistent among light levels; however, scavenging was minimal during darkness. Of the 460 social interactions I observed, the majority (59%) were of low intensity and relatively few (15%) were of high intensity, and this was consistent among light levels. Among 45 high intensity encounters observed between black and white morphs, black was dominant to white more frequently than vice versa (58%), but this effect occurred only during darkness and twilight. This study indicates that bears are able to maximize foraging opportunities within multiple temporal regimes through shifts in sensory systems and by altering their behaviour according to light level. Keywords: sensory modes; nocturnal behaviour; colour polymorphism; niche partitioning; foraging; black bear; Ursus americanus; Kermode bear; Ursus arctos; Salmon; Oncorhynchus; stable isotopes; activity patterns; social interactions; night vision; British Columbia Table of contents .. Abstract ...............................................................................................ii ... Table of contents.................................................................................... 111 List of tables ........................................................................................vii .. List of figures ......................................................................................vw ... Acknowledgements .................................................................................xi Chapter 1: General Introduction............................................................... 1 1.1 Sensory modes and colour variability .................................................... 1 1.2 Ursus americanus kermodei ................................................................. 4 Chapter 2: Site description and general methodology .....................................10 2.1 Site description ............................................................................. 10 2.2 General methodology ...................................................................... 13 Chapter 3: Behavioural activity patterns among light levels in a polymorphic bear population .........................................................................................-15 3.1 Introduction .................................................................................. 15 3.2 Methods and Materials ...................................................................... 18 3.2.1 Temporal activity patterns: scan samples....................................... 18 3.2.2 Individual time budgets ........................................................... 18 3.3 Results ......................................................................................... 22 3.3.1 Temporal activity patterns: scan samples ...................................... 22 3.3.1. 1 Overall ..................................................................... 22 3.3.1.2 Light level effects ......................................................... 22 3.3.1.3 Colour morph effects ..................................................... 22 3.3.1.4 Colour and light level effects ............................................ 26 3.3.1.5 Salmon density effects .................................................... 26 3.3.2 Individual time budgets ........................................................... 30 3.3.2.1 Overall ....................................................................... 30 3.3.2.2 Feeding time proportions ................................................. 30 3.3.2.2.1 Overall ............................................................. 30 3.3.2.2.2 Light level effects ................................................ 30 3.3.2.2.3 Colour morph effects ............................................ 31 3.3.2.3 Feeding time durations ................................................... 37 3.3.2.3.1 Light level effects ............................................... -37 3.3.2.3.2 Colour morph effects ............................................ 37 3.3.2.4 Non-feeding time proportions ........................................... 40 3.3.2.4.1 Overall .............................................................. 40 3.3.2.4.2 Light level effects ............................................... 40 3.3.2.4.3 Colour morph effects ............................................ 40 3.3.2.5 Non-feeding time durations .............................................41 3.3.2.5.1 Light level effects ............................................... 41 3.3.2.5.2 Colour morph effects ........................................... 42 3.4 Discussion .................................................................................... 48 3.4.1 Temporal activity patterns ........................................................ 48 3.4.2 Individual time budgets: Feeding ............................................... -51 3.4.3 Individual time budgets: Non-feeding ........................................ S4 Chapter 4: Foraging performance among different light environments of a polymorphic bear population................................................................... 56 4.1 Introduction .................................................................................. 56 4.2 Methods and Materials ..................................................................... 61 4.3 Results ........................................................................................ 64 4.3.1 Fishing Technique ................................................................. 64 4.3.2 Capture Efficiency ............................................................... 65 4.3.2.1 Light level effects ........................................................ 65 4.3.2.2 Technique effects ......................................................... 65 4.3.2.3 Light level and technique interactions .................................65 4.3.2.4 Colour morph and interactions .......................................... 66 4.3.3 Capture Rates .................................................................... -73 4.3.3.1 Year effects ............................................................... 73 4.3.3.2 Light level effects ........................................................ 73 4.3.3.3 Colour morph and light level effects .................................. 73 4.3.3.4 Foraging bout length effects ............................................ 74 4.3.4 Salmon activity patterns ......................................................... 77 4.3.5 Acoustic cues: speaker ........................................................... 77 4.4 Discussion .................................................................................. -79 . 4.4.1 Fishing technique .................................................................. 79 4.4.2 Efficiency .......................................................................... 80 4.4.3 Fishing technique and efficiency................................................ 81 4.4.4 Colour morph effects .............................................................. 83 4.4.5 Capture rates ....................................................................... 86 Chapter 5: Behavioural responses of salmon to a model predator among variable light regimes........................................................................................ 88 5.1 Introduction .................................................................................. 88 5.2 Methods and Materials ..................................................................... 90 5.2.1 Experimental pool ................................................................. 90 5.2.2 Simulating