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Effects of a flooding event on a threatened black bear population in Louisiana

Authors

  • K. C. O'Connell-Goode,

    1. Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, USA
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  • C. L. Lowe,

    1. Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, USA
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  • J. D. Clark

    Corresponding author
    1. US Geological Survey, Southern Appalachian Research Branch, University of Tennessee, Knoxville, TN, USA
    • Correspondence

      Joseph Clark, US Geological Survey, Southern Appalachian Research Branch, 274 Ellington Plant Sciences Building, University of Tennessee, Knoxville, TN 37996, USA. Tel.: 865 974 4790.

      Email: jclark1@utk.edu

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  • Editor: Res Altwegg
  • Associate Editor: Vincenzo Penteriani

Abstract

The Louisiana black bear, Ursus americanus luteolus, is listed as threatened under the Endangered Species Act as a result of habitat loss and human-related mortality. Information on population-level responses of large mammals to flooding events is scarce, and we had a unique opportunity to evaluate the viability of the Upper Atchafalaya River Basin (UARB) black bear population before and after a significant flooding event. We began collecting black bear hair samples in 2007 for a DNA mark-recapture study to estimate abundance (N) and apparent survival (φ). In 2011, the Morganza Spillway was opened to divert floodwaters from the Mississippi River through the UARB, inundating > 50% of our study area, potentially impacting recovery of this important bear population. To evaluate the effects of this flooding event on bear population dynamics, we used a robust design multistate model to estimate changes in transition rates from the flooded area to non-flooded area (ψFNF) before (2007–2010), during (2010–2011) and after (2011–2012) the flood. Average N across all years of study was 63.2 (se = 5.2), excluding the year of the flooding event. Estimates of ψFNF increased from 0.014 (se = 0.010; meaning that 1.4% of the bears moved from the flooded area to non-flooded areas) before flooding to 0.113 (se = 0.045) during the flood year, and then decreased to 0.028 (se = 0.035) after the flood. Although we demonstrated a flood effect on transition rates as hypothesized, the effect was small (88.7% of the bears remained in the flooded area during flooding) and φ was unchanged, suggesting that the 2011 flooding event had minimal impact on survival and site fidelity.

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