Effects of environmental variables on invasive amphibian activity: using model selection on quantiles for counts

Muller, Benjamin J., Cade, Brian S., and Schwarzkopf, Lin (2018) Effects of environmental variables on invasive amphibian activity: using model selection on quantiles for counts. Ecosphere, 9 (1). e02067.

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Abstract

Many different factors influence animal activity. Often, the value of an environmental variable may influence significantly the upper or lower tails of the activity distribution. For describing relationships with heterogeneous boundaries, quantile regressions predict a quantile of the conditional distribution of the dependent variable. A quantile count model extends linear quantile regression methods to discrete response variables, and is useful if activity is quantified by trapping, where there may be many tied (equal) values in the activity distribution, over a small range of discrete values. Additionally, different environmental variables in combination may have synergistic or antagonistic effects on activity, so examining their effects together, in a modeling framework, is a useful approach. Thus, model selection on quantile counts can be used to determine the relative importance of different variables in determining activity, across the entire distribution of capture results. We conducted model selection on quantile count models to describe the factors affecting activity (numbers of captures) of cane toads (Rhinella marina) in response to several environmental variables (humidity, temperature, rainfall, wind speed, and moon luminosity) over eleven months of trapping. Environmental effects on activity are understudied in this pest animal. In the dry season, model selection on quantile count models suggested that rainfall positively affected activity, especially near the lower tails of the activity distribution. In the wet season, wind speed limited activity near the maximum of the distribution, while minimum activity increased with minimum temperature. This statistical methodology allowed us to explore, in depth, how environmental factors influenced activity across the entire distribution, and is applicable to any survey or trapping regime, in which environmental variables affect activity.

Item ID: 53157
Item Type: Article (Research - C1)
ISSN: 2150-8925
Keywords: animal activity; cane toad; model selection; quantile count model; quantile regression; Rhinella marin
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© 2018 Muller et al. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A version of this publication was included as Chapter 2 of the following PhD thesis: Muller, Benjamin John (2018) An examination of cane toad (Rhinella marina) behaviour: how can we use this knowledge to refine trapping regimes? PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Research Council (ARC)
Projects and Grants: ARC Linkage Grant LP10020032
Date Deposited: 24 Apr 2018 01:55
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060207 Population Ecology @ 100%
SEO Codes: 96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960404 Control of Animal Pests, Diseases and Exotic Species in Forest and Woodlands Environments @ 100%
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