Not accounting for interindividual variability can mask habitat selection patterns: a case study on black bears
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Habitat selection studies conducted at the population scale commonly aim to describe general patterns that could improve our understanding of the limiting factors in species–habitat relationships. Researchers often consider interindividual variation in selection patterns to control for its effects and avoid pseudoreplication by using mixed-effect models that include individuals as random factors. Here, we highlight common pitfalls and possible misinterpretations of this strategy by describing habitat selection of 21 black bears Ursus americanus. We used Bayesian mixed-effect models and compared results obtained when using random intercept (i.e., population level) versus calculating individual coefficients for each independent variable (i.e., individual level). We then related interindividual variability to individual characteristics (i.e., age, sex, reproductive status, body condition) in a multivariate analysis. The assumption of comparable behavior among individuals was verified only in 40% of the cases in our seasonal best models. Indeed, we found strong and opposite responses among sampled bears and individual coefficients were linked to individual characteristics. For some covariates, contrasted responses canceled each other out at the population level. In other cases, interindividual variability was concealed by the composition of our sample, with the majority of the bears (e.g., old individuals and bears in good physical condition) driving the population response (e.g., selection of young forest cuts). Our results stress the need to consider interindividual variability to avoid misinterpretation and uninformative results, especially for a flexible and opportunistic species. This study helps to identify some ecological drivers of interindividual variability in bear habitat selection patterns.
KeywordsIndividual habitat selection pattern Intrinsic characteristic Multivariate analyses Random slope coefficient
We thank C. Dussault, S. Gravel, D. Grenier, C. Harvey and G. Lupien for bear captures, as well as A. Bérubé-Deschênes, K. Bédard, N. Bradette, C. Chicoine, J. Fillion, M. Leclerc, J.-P. Marcoux, M. Serra-David and F. Taillefer for their assistance in the field. We also thank A. Caron for statistical advice, and D. Beauchesne, J. Martin, P. Legagneux, K. Malcolm, P. and M. Fast and three anonymous reviewers for useful comments on earlier versions of the manuscript.
Author contribution statement
Conceived and designed the experiments: R.L. M.H.S.L. Performed the experiments: R.L. MHSL. Analyzed the data: R.L. Contributed reagents/materials/analysis tools: M.H.S.L. Wrote the paper: R.L., M.H.S.L. Coordinated the funding of the project: M.H.S.L. Prepared, validated and submitted the capture protocol to the Canadian Council on Animal Care: M.H.S.L.
Compliance with ethical standards
Black bear captures were conducted by the technicians of the Ministère des Forêts, de la Faune et des Parcs du Québec (hereafter MFFP) in June and July 2011 and 2012. All manipulations were approved by the Animal Welfare Committees of the MFFP and of the Université du Québec à Rimouski (certificate #2011-30).
This project was funded by the Fonds de recherche du Québec—Nature et technologies and the Fonds de recherche forestière du Saguenay–Lac-St-Jean (Grant #2011-FS-141452 to M.-H. St-Laurent), the Natural Sciences and Engineering Research Council of Canada (Grant #386661-2010 to M.-H. St-Laurent), the Ministère des Forêts, de la Faune et des Parcs du Québec, Resolu Forest Products Inc. and the Université du Québec à Rimouski.
Conflict of interest
The authors declare that they have no conflict of interest.
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