DOI: 10.5061/dryad.t4b8gthzd
title: Relationships between survival and habitat suitability of semi-aquatic mammals

description: Spatial distribution and habitat selection are integral to the study of
 animal ecology. Habitat selection may optimize the fitness of individuals.
 Hutchinsonian niche theory posits the fundamental niche of species would
 support the persistence or growth of populations. Although niche-based
 species distribution models and habitat suitability models (HSMs) such as
 maximum entropy (Maxent) have demonstrated fair to excellent predictive
 power, few studies have linked the prediction of HSMs to demographic
 rates. We aimed to test the prediction of Hutchinsonian niche theory that
 habitat suitability (i.e., likelihood of occurrence) would be positively
 related to survival of American beaver (Castor canadensis), a North
 American semi-aquatic, herbivorous, habitat generalist. We also tested the
 prediction of ideal free distribution that animal fitness, or its
 surrogate, is independent of habitat suitability at the equilibrium. We
 estimated beaver monthly survival probability using the Barker model and
 radio telemetry data collected in northern Alabama, United States from
 January 2011 to April 2012. A habitat suitability map was generated with
 Maxent for the entire study site using landscape variables derived from
 the 2011 National Land Cover Database (30-m resolution). We found an
 inverse relationship between habitat suitability index and beaver
 survival, contradicting the predictions of niche theory and ideal free
 distribution. Furthermore, four landscape variables selected by American
 beaver did not predict survival. The beaver population on our study site
 has been established for 20 or more years and, subsequently, may be
 approaching or have reached the carrying capacity. Maxent-predicted
 increases in habitat use and subsequent intraspecific competition may have
 reduced beaver survival. Habitat suitability-fitness relationships may be
 complex and, in part, contingent upon local animal abundance. Future
 studies of mechanistic species distribution models incorporating local
 abundance and demographic rates are needed.
description: <strong>Radio telemetry data
 collection</strong> We captured American beaver
 using Hancock live traps (Hancock Trap Company, Custer, SD, USA) within
 Redstone from January to May 2011. We fit a 38-g (&lt;0.05% of body
 mass) very high frequency (VHF) transmitter (Model 3530, Advanced
 Telemetry Systems, Isanti, MN, USA) to each captured subadult (10.9–16.0
 kg) and adult (&gt;16 kg) using tail-mounting methods; juveniles were
 excluded (Arjo et al. 2008, McClintic et al. 2014a). Smith et al. (2016)
 demonstrated that tail-mounting did not affect beaver survival in
 Minnesota. Capture and handling of beavers was approved by the
 Institutional Animal Care and Use Committee of the United States
 Department of Agriculture, National Wildlife Research Center (Protocol No.
 QA-1626). For survival analysis, we located radio-tagged beaver once every
 four weeks (i.e., tracking occasions) to determine the fates (i.e., live,
 dead, undetected, or missing) of radio-tracked individuals from January
 2011 to April 2012. We determined additional information on the fates of
 tracked beaver from other relocations collected via triangulation between
 tracking occasions (for home range estimation in a different study) and
 used those live resighting or dead recovery data for the Barker survival
 model. We located dead beaver as practically possible by triangulation on
 the VHF mortality signal.  <strong>Encounter
 history input for program MARK</strong> For the
 encounter history input, we used monthly live detections (completed during
 the first week of a monthly interval) of radio-tagged individuals via VHF
 telemetry as a live encounter occasion. Live detections occurring anytime
 between the two successive live encounter occasions within a month were
 treated as live resightings <strong>Environmental
 covriates</strong> <em>The normalized
 difference vegetation index (NDVI) </em> We
 derived two monthly NDVI time series from 250-m resolution, 16-day MODIS,
 multi-spectral satellite imagery using R package MODIStsp. The NDVI time
 series included: (1) NDVI for Redstone’s entire American beaver population
 for each monthly tracking interval (popndvi); and (2) wetland- or
 colony-specific NDVI for each monthly tracking interval (colndvi). We
 delineated the spatial extent of beaver colonies using a minimum convex
 polygon from all VHF locations of all radio-tagged beaver inhabiting a
 wetland. We averaged NDVI values over all cells or pixels within a colony
 to estimate colony-specific NDVI using R packages raster and sp. If a
 radio-tracked individual did not occupy a known colony, we extracted NDVI
 values by using a circular buffer representing the average spatial extent
 of beaver colonies. The circular buffer was centered at the centroid of
 the VHF locations of the individual. Variable popndvi was calculated as
 the average of all colndvi values by month.  Lanscape
 variables To evaluate landscape-beaver survival
 relationships, we included landscape variables: woody wetland edge density
 (m ha<sup>-1</sup>, wwetbd), shrub edge density (shrubbd),
 water body edge density (waterbd), and relative frequency (0-1.0) of
 grassland (grassfq) out of 30 landscape variables. We derived raster
 layers for these four landscape variables from 2011 National Land Cover
 Database (NLCD) using the program Biomapper. We calculated averages of the
 four landscape variables for each colony using the same geospatial
 analysis as we did for NDVI.
description: The data input file includes the inline note for explanations by
 column, serving as metadata.  There are no missing values in the input
 data.