Animal deaths, both natural and resulting from humane euthanasia, related to helicopter roundups of feral equids occur at a similar rate as deaths related to bait-trapping—another method used to gather wild horses—said John Derek Scasta, PhD, of the University of Wyoming’s Department of Ecosystem Science and Management, in Laramie. In either scenario, the death rate is significantly lower than that found in roundups of other wild animal species, he said.
10 years of capture data scoped
Scasta recently reviewed 10 years’ worth of Bureau of Land Management (BLM) data on the capture of wild mustangs and burros. The 70 captures from 2010 to 2019 involved nearly 29,000 horses and more than 2,000 burros in nine states (Arizona, California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, and Wyoming). There were 36 helicopter gathers and 34 bait-trapping gathers. During helicopter gathers, horses are driven by a helicopter that flies behind and slightly above the herd until the horses reach an enclosure. In bait-trapping, the horses freely enter a wide enclosure that contains water or food, without human presence. A hidden ground crew closes the gate with remote control.
Across the decade of data, 96 horses and four burros died or were euthanized during or just after the bait-trap gathers, and 268 horses died during or just after the helicopter gathers, said Scasta. (Based on the information available, the BLM does not routinely carry out helicopter gathers on burros, he added.) This yields a mortality rate of 1.7% for bait-trap gathers and 1.0% for helicopter gathers.
These captures are associated with far fewer deaths than similar roundups (usually for scientific research projects) of elk, deer, and caribou, which have reported mortality rates up to 20%, Scasta said. “In the scientific community it’s generally considered that anything over 2% is unacceptable,” he said.
Importantly, he added, a few horse gathers conducted during emergency situations had mortality rates upward of 3.5% and 10.5%, likely due to the horses’ emaciated conditions. Another gather had a mortality rate of 3.5% due to a prevalence of genetically related structural deformations and lameness, according to the study.
Most of the deaths (more than threefold) related to wild horse and burro roundups in the U.S.—regardless of method—result from pre-existing or chronic conditions, explained Scasta. Some animals arrive in holding pens with poorly healed old injuries—broken limbs, necks, and backs—or other debilitating conditions such as blindness, lameness, club feet, or poor body condition (sometimes related to advanced age and/or poor dental health), among others. Veterinarians and trained horse and burro specialists present at the roundups humanely euthanize animals with advanced cases, he said.
Some horses and burros died during roundups due to cardiac arrest, fractures, or capture myopathy—a term essentially referring to the fatal shock of being captured, he said.
Scasta noted that mortality reporting and helicopter pilot training appear to have improved over the past years. “Helicopter pilots are well-trained to work with horses, keeping a certain distance and slowing down to make sure the horses aren’t running constantly,” he said. “So that actually makes these captures less traumatic than people often think.”
Animal Centered Decision Making
Although bait-trapping allows animals to choose to enter an enclosure to access food or water, these enclosures are usually placed in very remote areas, Scasta explained. As a result, the horses, once captured, must load into trucks and travel over rough terrain for long distances. In helicopter roundups, the horses cross these terrains themselves and then have relatively short transportation times by truck on smoother roads.
“So even when you’re talking about their stress levels—which haven’t been adequately researched yet—how they differ relative to capture techniques is largely unknown,” he said.
While any roundup death might seem unacceptable, not rounding up feral equids can also result in loss of life, Scasta said. “They might die slowly from injury, disease, or starvation due to overpopulation,” he explained. Predator attacks, mainly by mountain lions, probably occur as well, but little research has been carried out in that field. “All these horses will come to the end of their lives in some way,” he said. “As a society we have to ask, ‘What is the most humane scenario for that to happen in?’”