While compassionate conservationists themselves are thankfully very much a minority in the scientific community, there is one situation where they'll be more listened to by a group of people. That situation is the issue with wild horses in Western North America. Contrary to other introduced species, these horses are given protection by the federal government via a bill signed into law in 1971. So in this situation, culling isn't used; instead, the horses are rounded up to control their numbers.
Since then when you think about it, feral horses are the perfect symbol for the compassionate conservation movement, as you constantly hear horse advocates say they're replacing extinct horses and bring ecological benefits. And to tell the truth, I bought into this idea. I used to be on the Mustang's side, and I think this was in part influenced by the fact that I grew up watching
Spirit: Stallion of the Cimmaron.
And I'll admit, it's only recently that I've learned how wrong I was.
Here I'll make a list of abstracts for studies on feral horse interactions with native ungulates.
1.)
Interactions between Feral Horses and Desert Bighorn Sheep at Water
"We studied sympatric populations of native bighorn sheep (
Ovis canadensis) and feral horses (
Equus caballus) to quantify their spatial and temporal overlap and to determine whether horses interfered with use of water by bighorn sheep. We observed no evidence of direct competition, but our field experiment, which involved placing desert-acclimated domestic horses near watering sites used by bighorn sheep, demonstrated that bighorn sheep avoided sites with horses nearby. The presence of domestic horses near a watering site preferred by bighorn sheep resulted in a 76% reduction in the number of groups of bighorn sheep coming to water at that location and a concomitant increase in the number of bighorn sheep watering at other sites. An experimental approach to studying competition between large mammals has been problematic and to our knowledge this study constitutes the 1st manipulative field experiment to test for competitive interactions between feral horses and native ungulates."
2.)
https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.2096
"The horse (
Equus caballus) is a feral ungulate that currently exceeds target population sizes in many areas of western North America. Horses are behaviorally dominant over native ungulates and outcompete the latter for access to water sources. However, a better understanding of the broader spatial and temporal implications of horse-induced competition on access to water by native ungulates will enable better conservation and management of native species. Our objective was to determine whether pronghorn (
Antilocapra americana) and mule deer (
Odocoileus hemionus) spatially or temporally altered their use of water to minimize interactions with horses. From 2010 to 2014, we used remote cameras to monitor ungulates at 32 water sources in the Great Basin Desert. We evaluated spatial and temporal partitioning by these species at water sources using generalized linear models, mixed-effects models, and Mann–Whitney
U tests. We found that both native ungulates used water sources less often where horse activity at water sources was high, indicating that spatial avoidance occurred. Further, we observed significant differences in peak arrival time for pronghorn, but not mule deer at horse-occupied sites versus sites where horses were absent or uncommon, indicating that temporal avoidance may be more important for pronghorn than mule deer. Because mule deer are primarily crepuscular and nocturnal whereas horses are largely diurnal, we did not expect to observe a temporal shift for mule deer. We also found strong support for the interactive negative effect of elevated temperature and subsequent increased activity of horses at water sources on drinking patterns of pronghorn and mule deer. Our findings indicate that feral horses further constrain access to an already limited resource for native species in a semi-arid environment."
3.)
https://bioone.org/journals/the-sou...Feral-Horses/10.1894/0038-4909-60.4.390.short
"We used a motion-triggered camera to document and qualify the nature of interspecific interactions between elk (
Cervus elaphus) and feral horses (
Equus caballus) at an isolated, natural water source in Mesa Verde National Park, Colorado. The camera was active for at least 110 of 145 potential trap-nights between 24 April 2012 and 16 September 2012. Elk and horse interactions were observed 51 times, and elk were averted from accessing water 42 times (82%). Feral horses exhibited dominant behavior over native elk during the driest time of the year (May–June), often preventing acquisition of water by elk."
4.)
https://www.researchgate.net/public...horses_on_pronghorn_behavior_at_water_sources
"Feral horses (Equus callabus) occur throughout the world on all continents except Antarctica. In North America, feral horses occupy 31.6 million acres throughout western North America. Throughout their range, feral horses often share habitat with American pronghorn (Antilocapra americana). Since horses are larger and more aggressive than pronghorn, they are considered socially dominant. In the Great Basin of western North America, pronghorn often access water sources where horses occur since habitat preferences are similar. If pronghorn are excluded where water is used by both species, pronghorn fitness may be impaired, especially during dry or droughty periods. The purpose of this study was to investigate interference competition between pronghorn and feral horses at water sources within the Great Basin. We observed horses and pronghorn at high-use water sources and recorded all occurrences and outcomes of pronghorn/horse interactions. We assessed differences in pronghorn behavior in the presence or absence of horses. Pronghorn invested more time on vigilance behavior and less time foraging or drinking in the presence of horses than in their absence. Nearly half of pronghorn/horse interactions resulted in pronghorn exclusion from water. We conclude that as feral horse numbers increase, competition for water will subsequently increase."
5.)
https://www.sciencedirect.com/science/article/pii/S014019631530094X
"Introduced species can impact native communities by altering competition dynamics. Large exotic species, such as the horse (
Equus caballus), may have a competitive advantage over smaller native species and could exclude them from access to limited resources. Our objective was to determine the influence of the exotic horse on the use of water by native species in a semi-arid environment where availability of water is limited. From July 2010 to August 2011, we used remote cameras to monitor water sources in the Great Basin Desert where horses had drinking access and where horses were excluded (with fencing) to compare 1) composition of native communities and 2) water usage by native species. We captured 96,601 images representing 40 species of birds (29,396 images) and 13 species of mammals (67,205 images). Of the 67,205 images of mammals, 79% contained horses. Horses were associated with decreased richness and diversity of native species at water sources. Furthermore, native species had fewer visits and spent less time at water sources frequented by horses. Our results indicated that horses displaced other species at water sources providing evidence of a negative influence on how communities of native wildlife access a limited resource in an
arid environment."
From these studies, it's very clear that mustangs are an invasive species. And the worst part about this? This is something people have allowed to happen. Horse advocates complain that holding so many horses in the pens is cruel, but this wouldn't be an issue if conservationists were able to control the horse population. The entire reason the dumb law protecting them exists was due to pressure from people who were angry about wild horse management. And now both the native wildlife and the horses themselves are paying the price for it.