Allen Rutberg and John Turner: BLM should use PZP to rein in wild horse population

The Bureau of Land Management has a tough job managing wild horses. If they propose a gather, or don’t gather enough, they get sued. If, through drought or agency inaction, forage and water on the range are exhausted and horses die, the public explodes with rage.

Meanwhile, wild horses keep reproducing and filling holding facilities at breathtaking costs to the taxpayer. Even in the best facilities, the lives of the newly captive horses do not remotely resemble their lives on the range.

Reducing wild horse population growth using contraception is an obvious solution. This is hardly news to the BLM, which has been funding such research, including ours, for 40 years. We’re grateful for it.

But at some point, studying must yield to doing. And here, BLM lags.

The National Park Service has been managing the wild horses of Assateague Island National Seashore in Maryland with the PZP (porcine zona pellucida) contraceptive vaccine since 1994. Now, nearly all the Atlantic Coast barrier island wild horses are being managed with PZP, with barely a ripple of concern from the public.

But that’s different, says the BLM. Those horses are much more approachable, and can be darted and redarted with the vaccine as needed. We can’t do that out West.

That’s mostly true.

But, in our view, it’s NOT why NPS is succeeding where BLM is failing.

The crucial difference is that the NPS has developed careful, detailed management plans, whereas BLM has not even tried. For each site, NPS prescribes management goals, how many horses should be treated and which ones. They adapt their management plans as conditions change and goals are met, or not.

By contrast, half a dozen scattered BLM herd management areas manage herds with PZP. Other HMAs have used PZP haphazardly, without strategic goals or evaluation of success. BLM-sponsored research pursues the quick fix that will solve its billion-dollar horse problem. But no technical solutions will work without a systemwide implementation plan.

In the latest twist, BLM has backed off a volunteer-driven PZP project at Pine Nut Mountain HMA because of legal threats from a Connecticut animal rights group. This group must shroud its advocacy in legal action and pseudoscience because its solution to capping wild horse populations is “natural regulation,” which is code for mass starvation. To everyone else, that’s intolerable.

PZP works. Its major side effect is that, spared the energy drain of pregnancy and nursing, PZP-treated mares display better physical condition than mares with foals.

To reduce herd population growth and keep wild horses in their bands at home and out of holding facilities, PZP must be applied systematically and thoughtfully. We understand that most HMAs don’t have NPS’s capacity to track and treat individual mares. But there’s a lot of middle ground between that approach and “treat all mares released back to the HMA.” BLM must explore that ground, and plan, or continue to fail.

We’re scientists. We’re all for research. But for goodness sake, when it works, use it.

Allen Rutberg, Ph.D. is director of the Center for Animals and Public Policy for the Cummings School of Veterinary Medicine at Tufts University. .John W. Turner, Jr, Ph.D. is a professor of physiology and pharmacology at the University of Toledo College of Medicine and Life Sciences. Dr. Rutberg and Dr. Turner have been conducting and publishing studies on wild horse contraception and behavior for more than 30 years.