Mortality among free-ranging California condors (Gymnogyps californianus) during 2010–2014 with determination of last meal and toxicant exposure

Authors

  • Tabitha Viner DVM DACVP US Fish and Wildlife Service, National Forensics Laboratory, 1490 East Main Street, Ashland, OR 97520-1310 USA
  • Rebecca Kagan DVM DACVP US Fish and Wildlife Service National Forensics Laboratory
  • Bruce Rideout DVM PhD DACVP Disease Investigations, Institute for Conservation Research, San Diego Zoo Global
  • Ilse Stalis DVM Disease Investigations, Institute for Conservation Research, San Diego Zoo Global (formerly)
  • Rebecca Papendick DVM DACVP Disease Investigations, Institute for Conservation Research, San Diego Zoo Global (formerly)
  • Allan Pessier DVM DACVP Disease Investigations, Institute for Conservation Research, San Diego Zoo Global https://orcid.org/0000-0002-2996-1433
  • Margaret E Smith MS US Fish and Wildlife Service National Forensics Laboratory (formerly)
  • Mary Burnham-Curtis PhD https://orcid.org/0000-0002-4332-4801
  • Brian Hamlin BS US Fish and Wildlife Service National Forensics Laboratory https://orcid.org/0000-0002-7026-4832

DOI:

https://doi.org/10.32473/jvfs.v1i2.128637

Keywords:

lead, diet, pathology, genetics, toxicology, California Condors, Gymnogyps californianus

Abstract

Over the past 30 years, the California condor (Gymnogyps californianus) population has rebounded from 22 individuals to over 200 birds living in the wild. Historical impacts to the population have been largely anthropogenic. In this study, we explore mortality and cause of death data from condors that died during the years 2010-2014 and compare these to mortality data described by Rideout et al. in 2012, covering the years 1992-2009. In addition, morphologic and genetic analysis of the contents of the upper gastrointestinal (GI) tract was performed on the 2010-2014 condor mortalities to determine animal origins of the last meal eaten. The maximum population at risk within this time frame was 329 birds. During this time, 88 condors died and underwent post-mortem examination, and 41 birds were lost to tracking efforts and presumed dead (crude mortality rate of 39%; 129/329). A cause of death was determined for 66 of the 88 necropsied birds. Lead toxicosis remained a significant negative factor in condor population recovery, being related to the deaths of 37 adult and juvenile condors (proportional mortality rate 56%). Compared to condors succumbing to other causes of death, cattle were less often part of the last meal of lead-intoxicated condors. Based on these data, continued efforts to mitigate the impact of lead on California condors should be pursued.

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Black and white charcoal illustration of California condor (Artist: Susan Underkoffler)

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Published

2020-11-01

Issue

Vol. 1 No. 2 (2020)

Section

Wildlife

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Copyright (c) 2020 Tabitha Viner

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