Solving the sample size problem for resource selection functions
- Department of Wildlife, Fisheries, and Aquaculture Mississippi State University Mississippi State MS USA, Quantitative Ecology and Spatial Technologies Laboratory Mississippi State University Mississippi State MS USA
- School of Mathematics and Statistics University of Sheffield Sheffield UK
- Department of Biosciences Swansea University Swansea UK, Centre for Biomathematics Swansea University Swansea UK
- Savannah River Ecology Laboratory University of Georgia Aiken SC USA
- Department of Wildlife, Fisheries, and Aquaculture Mississippi State University Mississippi State MS USA
- Department of Integrative Biology University of Guelph Guelph ON Canada
- Department of Biology University of Saskatchewan Saskatoon SK Canada
- Haub School of Environment and Natural Resources University of Wyoming Laramie WY USA
- Department of Biology Memorial University of Newfoundland St. John’s NL Canada
- Instituto de Biosciências Universidad Estadual Paulista Rio Claro, São Paulo Brazil
- Centre for Northern Forest Ecosystem Research Ontario Ministry of Natural Resources and Forestry ON Canada
- Department of Bioscience Aarhus University Aarhus Denmark
- Wyoming Cooperative Fish and Wildlife Research Unit University of Wyoming Laramie WY USA
- IUCN/SSC Peccary Specialist Group Campo Grande Brazil
Sample size sufficiency is a critical consideration for estimating resource selection functions (RSFs) from GPS‐based animal telemetry. Cited thresholds for sufficiency include a number of captured animals and as many relocations per animal N as possible. These thresholds render many RSF‐based studies misleading if large sample sizes were truly insufficient, or unpublishable if small sample sizes were sufficient but failed to meet reviewer expectations.
We provide the first comprehensive solution for RSF sample size by deriving closed‐form mathematical expressions for the number of animals M and the number of relocations per animal N required for model outputs to a given degree of precision. The sample sizes needed depend on just 3 biologically meaningful quantities: habitat selection strength, variation in individual selection and a novel measure of landscape complexity, which we define rigorously. The mathematical expressions are calculable for any environmental dataset at any spatial scale and are applicable to any study involving resource selection (including sessile organisms). We validate our analytical solutions using globally relevant empirical data including 5,678,623 GPS locations from 511 animals from 10 species (omnivores, carnivores and herbivores living in boreal, temperate and tropical forests, montane woodlands, swamps and Arctic tundra).
Our analytic expressions show that the required M and N must decline with increasing selection strength and increasing landscape complexity, and this decline is insensitive to the definition of availability used in the analysis. Our results demonstrate that the most biologically relevant effects on the utilization distribution (i.e. those landscape conditions with the greatest absolute magnitude of resource selection) can often be estimated with much fewer than animals.
We identify several critical steps in implementing these equations, including (a) a priori selection of expected model coefficients and (b) regular sampling of background (pseudoabsence) data within a given definition of availability. We discuss possible methods to identify a priori expectations for habitat selection coefficients, effects of scale on RSF estimation and caveats for rare species applications. We argue that these equations should be a mandatory component for all future RSF studies.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1814655
- Journal Information:
- Methods in Ecology and Evolution (Online), Journal Name: Methods in Ecology and Evolution (Online) Journal Issue: 12 Vol. 12; ISSN 2041-210X
- Publisher:
- Wiley-BlackwellCopyright Statement
- Country of Publication:
- United Kingdom
- Language:
- English