Intrapopulation diversity in isotopic niche over landscapes: Spatial patterns inform conservation of bear–salmon systems

Trisalyn Nelson,Megan S Adams,Taal Levi,Andrew Bateman,Chris T Darimont,Mathieu Bourbonnais,Christina N Service,Paul C Paquet,Kyle A Artelle

doi:10.1002/ecs2.1843

Abstract

AbstractIntrapopulation variability in resource acquisition (i.e., niche variation) influences population dynamics, with important implications for conservation planning. Spatial analyses of niche variation within and among populations can provide relevant information about ecological associations and their subsequent management. We used stable isotope analysis and kernel‐weighted regression to examine spatial patterns in a keystone consumer–resource interaction: salmon (Oncorhynchus spp.) consumption by grizzly and black bears (Ursus arctos horribilis, n = 886; and Ursus americanus, n = 557) from 1995 to 2014 in British Columbia (BC), Canada. In a region on the central coast of BC (22,000 km2), grizzly bears consumed far more salmon than black bears (median proportion of salmon in assimilated diet of 0.62 and 0.06, respectively). Males of both species consumed more salmon than females (median proportions of 0.63 and 0.57 for grizzly bears and 0.06 and 0.03 for black bears, respectively). Black bears showed considerably more spatial variation in salmon consumption than grizzlies. Protected areas on the coast captured no more habitat for bears with high‐salmon diets (i.e., proportions >0.5 of total diet) than did unprotected areas. In a continental region (~692,000 km2), which included the entire contemporary range of grizzlies in BC, males had higher salmon diets than females (median proportions of 0.41 and 0.04, respectively). High‐salmon diets were concentrated in coastal areas for female grizzly bears, whereas males with high‐salmon diets in interior areas were restricted to areas near major salmon watersheds. To safeguard this predator–prey association that spans coastal and interior regions, conservation planners and practitioners can consider managing across ecological and jurisdictional boundaries. More broadly, our approach highlights the importance of visualizing spatial patterns of dietary niche variation within populations to characterize ecological associations and inform management.

Highlights

Food and other resources are patchily distributed across space and time, creating what Hutchinson (1957) described as the “mosaic nature of the environment.” Consumers use multiple behavioral strategies to maximize resource exploitation in the context of this variation (Stephens and Krebs 1986, Fauchald 1999, Weimerskirch et al 2005)
Estimates of salmon consumption were more heterogeneous in male black bears than in grizzly bears among years and across space (Fig. 2)
Relative variability in salmon consumption was higher for black bears than for grizzly bears (black bears: Coefficient of variation (CV) = 1.44 for females, CV = 1.17 for males; grizzly bears: CV = 0.26 for females, CV = 0.15 for males)

Summary

Introduction

Food and other resources are patchily distributed across space and time, creating what Hutchinson (1957) described as the “mosaic nature of the environment.” Consumers use multiple behavioral strategies to maximize resource exploitation in the context of this variation (Stephens and Krebs 1986, Fauchald 1999, Weimerskirch et al 2005). Consumers use multiple behavioral strategies to maximize resource exploitation in the context of this variation (Stephens and Krebs 1986, Fauchald 1999, Weimerskirch et al 2005) These varied patterns of resource use, constrained by competition within and among species, comprise the spatial and temporal diversity of species’ realized niches (Hutchinson 1957, Chase and Leibold 2003, Kearney and Porter 2009). Protected areas aim to conserve regions of biodiversity and promote long-term ecological and genetic variation They can only represent portions of the habitat of most communities and the populations comprising them (Margules and Pressey 2000, Rodrigues and Gaston 2001, Chape et al 2005). The spatial configuration of protected areas can be guided and prioritized by the distribution of diverse life history strategies and ecological variation across landscapes (e.g., behavioral variation, Cooke et al 2014, species diversity, Brooks et al 2006), such that networks of protected areas prioritize fitness-related resource use within populations (Rodrigues et al 2004)

Methods

Results

Conclusion