Journal of equine veterinary science2019; 86; 102893; doi: 10.1016/j.jevs.2019.102893

Mortality and Operational Attributes Relative to Feral Horse and Burro Capture Techniques Based on Publicly Available Data From 2010-2019.

Abstract: Management of excessive feral horse (Equus ferus caballus) and burro (Equus asinus) populations in the United States and globally has been a controversial subject for decades. I reviewed all available US federal feral horse and burro daily gather reports from 2010 to 2019 to extract equine species, technique (bait trapping or helicopter gathering), reason (emergency or other), number gathered, number of mortalities, and mortality attributes (acute or chronic/pre-existing condition, specific cause). I found 70 reports (bait trapping burros n = 10, bait trapping horses n = 24, helicopter gathering horses n = 21) from 9 states (AZ, CA, CO, ID, MT, NV, OR, UT, WY) representing 28,821 horses and 2,005 burros. For bait trapping, 100 animals died (4 burros, 96 horses) with 16 acute causes (1 burro, 15 horses) and 84 chronic/pre-existing causes (3 burros, 81 horses). For helicopter gathering, 268 horses died with 62 acute causes and 206 chronic/pre-existing causes. Mortality ratios did not differ by capture technique (P > .05) for broken necks, emaciation, acute causes, or chronic/pre-existing causes. The most common mortality-causing problems were structural deformations, club foot, blindness, and emaciation. The more horses gathered per day resulted in a greater proportion of chronic/pre-existing mortalities for both trapping techniques, but only an increase of acute mortalities for helicopter gathering. The slope suggests 1 acute mortality for every 300 horses gathered. The capture mortality rate across all gathers [1.1% (368 mortalities out of 30,826 horses and burros captured)] is below a general threshold of 2% suggested for wildlife studies.
Publication Date: 2019-12-20 PubMed ID: 32067672DOI: 10.1016/j.jevs.2019.102893Google Scholar: Lookup
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This research article analyzes the mortality rates and characteristics relative to various capture techniques of feral horses and burros in the United States from 2010 to 2019. It suggests that the capture mortality rate is below the threshold suggested for wildlife studies.

Research Methodology

  • The researcher undertook a comprehensive review of publicly available daily gather reports for feral horses and burros in the United States from 2010-2019.
  • The study reviewed data from a number of states, including Arizona, California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, and Wyoming.
  • The capture techniques evaluated in the study included bait trapping and helicopter gathering.
  • From the data, the researcher extracted various details such as the equine species, capture technique, reason for gathering (either emergency or other), total number gathered, number of mortalities, and attributes of mortality (either acute or chronic/pre-existing condition, and specific cause).

Findings From the Research

  • The study analysed 70 reports that involved 28,821 horses and 2,005 burros.
  • During bait trapping, there were 100 fatalities (96 horses and 4 burros) broken down into 16 acute cases (15 horses and 1 burro) and 84 chronic/pre-existing condition cases (81 horses and 3 burros).
  • Helicopter gathering resulted in 268 horse deaths, divided into 62 acute and 206 chronic cases.
  • The mortality ratios did not significantly vary between the two capture techniques for acute causes, chronic/pre-existing causes, emaciation or broken necks.
  • The most frequently observed causes of death were structural deformations, club foot, blindness, and emaciation.
  • The number of horses gathered per day influenced the proportion of chronic/pre-existing mortalities in both capture techniques, however, an increase in acute mortalities was observed only in helicopter gathering.
  • The study proposed that for every 300 horses gathered, there seemed to be 1 acute mortality, based on the slope of the trend.
  • The overall capture mortality rate was considered to be below the generalized threshold of 2% suggested for wildlife studies, as there were 368 deaths out of 30,836 horses and burros captured, which is 1.1%.

Cite This Article

Scasta JD. (2019). Mortality and Operational Attributes Relative to Feral Horse and Burro Capture Techniques Based on Publicly Available Data From 2010-2019. J Equine Vet Sci, 86, 102893.


ISSN: 0737-0806
NlmUniqueID: 8216840
Country: United States
Language: English
Volume: 86
Pages: 102893
PII: S0737-0806(19)30642-2

Researcher Affiliations

Scasta, John Derek
  • Department of Ecosystem Science and Management, University of Wyoming, Laramie, WY. Electronic address:

MeSH Terms

  • Animals
  • Animals, Wild
  • Equidae
  • Horses
  • Mortality
  • United States / epidemiology


This article has been cited 2 times.
  1. Whiteman JP, Harlow HJ, Durner GM, Regehr EV, Amstrup SC, Pagano AM, Ben-David M. The acute physiological response of polar bears to helicopter capture.. J Wildl Manage 2022 Jul;86(5):e22238.
    doi: 10.1002/jwmg.22238pubmed: 35915725google scholar: lookup
  2. Rou015fu O, Melega I, Evans AL, Arnemo JM, Ku00fcker S. Evaluation of Medetomidine-Ketamine for Immobilization of Feral Horses in Romania.. Front Vet Sci 2021;8:655217.
    doi: 10.3389/fvets.2021.655217pubmed: 34235198google scholar: lookup