The main thrust for the reduction of wild horse herds in the Alberta foothills is from grazing leaseholders concerned that horses are consuming forage at the expense of their cattle. How valid is this assumption? I have only been able to find one study, by Salter & Hudson, that looks at how horses, wildlife and cattle impact our foothills ecosystem. I have used this study and other more general ones to try to put the issue into perspective.
Grazing and the ecosystem
There appears to be agreement that grazing by ungulates is essential in maintaining a healthy ecosystem, particularly in grasslands. Ranchers contend that cattle have replaced bison as primary grazers, just as logging has replaced wildfires in forestry management. However this is rather simplistic and not entirely true as bison graze differently from cattle. In fact they graze more like horses as they tend to bite off the top parts of grass rather than tear away the near-ground shoots as do cattle. Also bison consumed a greater range of plants and tended to roam all over an area, including forested areas where they were able to browse on leaves.
How horses benefit the ecosystem
Horses graze by clipping grass using their upper and lower incisors, allowing it to easily grow back. In the summer growing season this provides lush green grass in meadows favored by elk and deer. They tend to nibble and move on, rarely denuding their range. They also help other species in winter by breaking through deep, crusted snow to expose the grass and by breaking ice at water sources with their powerful hooves. They range widely throughout their ranges, helping reduce dry inflammable vegetation in fire-prone areas and spreading seeds from their foraging through their unique digestive system that does not completely degrade the vegetation they eat. After drinking out of streams, they move away, causing little damage to the banks and leaving the water clean.
Effect of cattle on the ecosystem
Cows have no upper front teeth, only a thick pad. They graze by wrapping their long tongues around grass and pulling on it to cut it with their bottom teeth. If the ground is wet, they will pull out the grass by the roots, preventing it from growing back. Cattle tend to congregate near water and can do extensive damage to the riparian zones, trampling the ground, denuding the bushes that slow the force of floods and protect the banks, and eating sedges that filter out sediment. Trees such as willow, aspen, alder, and cottonwood disappear as mature trees die out and the young shoots are consumed.
Horses versus elk, moose and deer
Elk, moose and deer coexist with wild horses with little problem. While there is significant dietary overlap they seem to graze in different areas. In winter wildlife tend to browse in shrub meadows and mixed woods. During the cattle grazing season elk and deer prefer areas that have been grazed and have lush, green grass. Both elk and deer tend to graze in thickets and open woodland where there is cover from predators.
Horses versus cattle
The Salter study clearly indicates that horses and cattle forage on the same plants during the months that cattle are in the grazing leases. What is less clear is whether they compete for the same forage in the same areas at the same time. Observations suggest that cattle may overgraze an area and eat the more energy-giving and palatable forage, forcing horses to consume lower quality forage and other plants. Another researcher suggests that in mid-June, when cattle are brought to the grazing leases, the horses move to other areas, consuming less nutritious food, rather than competing with the cattle. Horses will feed farther away from water sources than cattle and will feed on lower quality plants that cattle reject. Spring grazing by horses does not deplete areas preferred later in the season by cattle.
Range conditions in the fall
Generally, range conditions in the areas favored by horses are much better than in those frequented by cattle. It would appear that the main cause of degradation of public lands is foraging by cattle. Salter observes that by the end of the summer grazing season, nearly half of the dry grasslands were heavily grazed and nearly all had received some degree of use. The depletion of fescues may adversely affect the amount of food available to both horses and elk in the subsequent winter.
There is no evidence that wild horses are destroying wildlife habitat, and there is no scientific proof that horses are foraging at the expense of cattle. On the contrary, there is plenty of evidence that wild horses are of benefit to the ecology of our foothills watersheds. How valid is the assumption that wild horses are consuming forage at the expense of their cattle? In my opinion not valid at all. Overgrazing and damage to riparian areas is by cattle. The solution to overgrazing is not to cull the wild horses (predators and hard winters will do that), but rather to reduce the number of cattle allowed on overgrazed leases.
Salter, R.E. & Hudson, R.J. Range Relationships of Feral Horses with Wild Ungulates and Cattle in Western Alberta.
Links to Wild Horses of Alberta Society (WHOA)
Official Wild Horses of Alberta Society (WHOA) site.