Wild Horses in the West

Eric Thacker grew up in Duchesne County, Utah. He attended Utah State University, where he obtained his BS and MS in Range Science and completed his PhD at Utah State in Wildlife Biology. Eric was employed at the USDA-ARS Poisonous Plant Research lab from 2000 – 2006. After completing his PhD in 2010 Eric moved to Oklahoma where he spent 2 years with the USDA-ARS Southern Plains Range Research Station and 1.5 years at Oklahoma State University. Eric is currently employed at Utah State University as the Range Extension Specialist. Eric has a wonderful (and patient) wife and 6 kids that take up most of his time when he is not working but when he can find some spare time he enjoys sampling rangeland fauna with a shotgun or flyrod.

Utah’s Rangelands

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Horses evolved on the North American landscape since the 1400s in a grassland ecosystem.  Yet, all of the wild horses that exist today across the western states live in deserts, sagebrush steppe, or other shrub dominated systems.  We talk with range scientist Eric Thacker about the growing number of wild horses across the west and the need for horse management in order to maintain the fragile ecosystems that they graze on.

Science Moab: Can you explain what makes these formerly domestic horses different from other truly wild animals?

Thacker: Wild horses are reproducing at a rate of 15 to 20% annually. I’m not aware of any other native wildlife species that’s reproducing annually at a rate of 15 to 20%. They’re off the charts in terms of reproduction potential. You’ve got this species that’s able to reproduce at a rate faster than any of its large mammal counterparts on a landscape. It lives as long or longer than those counterparts. And it is afforded more legal protection than any of the counterparts. It’s possible that these horses were selectively bred to reproduce at a higher rate than wild horses.

Science Moab: Are the horses in ecosystems that can handle having them?

Thacker: Horses evolved as a grassland steppe species. Few of our wild horses today are in grassland steppes. Most horses are in semi deserts, sagebrush steppe, or some other shrub dominated system, ecosystems that didn’t evolve with horses.To me, this is where the argument for management comes in, to make sure those habitats are protected. There’s also no strong population regulatory mechanism in wild horses. Other native ungulates have checks and balances within their population growth structure which help curb population.There’s even a whole predator community set up to help reduce those populations, but horses have no natural predators in North America.

Science Moab: Can you help us visualize the degradation that happens in these fragile ecosystems when large animals like these horses have been there a long time?

Thacker: First, they eat too much of the grasses, which can’t stay healthy because they can’t replenish their roots. There’s also increased trampling, which increases soil density, slowing the infiltration of water in the soil. Those two things feed back on themselves, so the soils become drier than they were previously, the animals are still there, the pressure on the remaining grasses increases. Then as the horses start running out of the forage they prefer, they start switching to other things, impacting the forage base of other species. Now, the system is reaching a point where it probably won’t recover without some significant input. Simply removing horses at this point won’t fix the problems. A lot of the areas with wild horses may have already crossed that threshold. And so it’s going to take incredible effort on our part to rebuild those systems. As a range ecologist, this is my biggest concern. As we lose that vegetation, we lose the ability to have many habitats which are affected by these degraded rangelands. Then at some point you start losing soil through erosion, and soil takes an incredibly long time to rebuild and form. So systems are reaching a point where they probably won’t fully recover.

Science Moab: Is there a relationship between cattle management and wild horse management on public lands?

Thacker: I hear arguments from horse advocates like wild horses only occur on 11% of BLM land, so they can’t be that big a problem. Then they’ll say there’s 2 million cattle AUMs and only 90,000 horses. There’s a certain amount of space and forage allotted for both cattle and horses by acts of Congress, so we should think about horse and cattle management in conjunction. The BLM has set numbers to maintain some level of sustainability, and simply removing cattle doesn’t solve the problem we’re experiencing, as horses are still a problem. We still have too many animals, meaning we still have degraded systems. The difference between cattle and horses is the BLM has ultimate control over how cattle grazing looks. They determine the timing and number of animals. With horses, there’s no current management mechanism that allows the BLM to be that flexible. Arguing over whether we should have more cows or more horses on ranch land is irrelevant until we solve the problem of how to manage wild horses.

Science Moab: How does the future look for horse management?

Thacker: The pessimistic view is that this problem could continue to grow, because there’s an argument that we can’t find the consensus on an appropriate way to manage horses to really deal with the problem. However, there’s a group called The Path Forward. It’s an interesting group that formed a management strategy, lobbied to Congress, and received 21 million additional dollars for wild horse management in 2020. But the basic premise of that whole management plan is, if we don’t do something now, this problem is only going to get much worse.