

Predator populations, their effects on sage-grouse populations, and issues surrounding predator control concern landowners, wildlife managers, and the public. Some people believe that predator populations have increased due to lack of predator control and that predators are the primary factor limiting sage-grouse populations. Others contend that habitat fragmentation and degradation are the primary reasons for population declines, and that these land use changes contribute to increased rates of predation.

Predation does impact sage-grouse to varying degrees. The impact of predation can vary as changes occur in the predator/prey environment seasonally, from year to year, and geographically. Many of Montana's native mammals, raptors, and other species such as ravens prey upon sage-grouse eggs, juveniles, and adults. Bull snakes are another species that can be an effective next predator. Invasive species like red fox and raccoon have expanded their range into sagebrush steppe communities and can impact the success of ground nesting birds. The quality and quantity of the sagebrush habitat, the composition of the predator community, and weather patterns such as drought or severe winters likely determine both the annual and long-term carrying capacity for sage-grouse. Sage-grouse populations in Montana appear to cycle from low to high numbers over a 10-year period, and these trends continue under the current combination of habitat, predation, and weather influences.

The composition and abundance of various avian and mammalian predator species has changed, and continues to change, since the termination of widespread predator control activities in the early 1970s. Changes in predator population composition and numbers may hold grouse numbers below their biological potential in some locations, even in areas characterized by largely unfragmented habitat.

Habitat fragmentation at the broad scale, which alters spatial relationships of remaining stands of sagebrush, potentially reduces the quantity of habitat. At the nest-site level, degradation of habitat through improper management can reduce the quality of sagebrush stands for nesting, most commonly by reducing the grass and forb understory. Both forms of habitat degradation can increase vulnerability of grouse and nests to the existing predator community, may alter the predator community, or both. Mammalian predator populations in degraded habitats often shift toward species that are smaller and more numerous (red fox, raccoon, striped skunk) and away from species that have evolved with sage-grouse (coyote, badger). Similar shifts in mammalian predator communities can also accompany intensive predator control programs, e.g., red fox numbers can increase when coyote populations are controlled. Furthermore, certain avian species such as gulls and ravens may have expanded their range, and their foraging behavior can potentially impact either nest success or juvenile survival rates in certain localities.

Intensive predator control programs can influence predator numbers at the local level, e.g. coyote control for livestock production and red fox and skunk trapping to protect upland nesting ducks. The practice is expensive, and the benefits are generally considered to be short-term because populations of most predators rebound rapidly after control stops. To date, predator control seldom has been recommended for North American prairie grouse for several reasons (Schroeder and Baydack, 2001). Nesting often is dispersed over vast areas, greatly increasing costs of control programs. The long-term biological consequences of predator control are poorly understood and may actually be counterproductive under some circumstances. Finally, many potential predators of sage-grouse are now legally protected, certain control methods such as poisons have been prohibited, and public attitudes towards predator control have changed (Messmer et al. 1999). However, if land use changes continue to degrade sagebrush habitats and the impacts of predators are shown to negatively impact sage-grouse populations, direct predator control actions may assume greater management importance (Nelson 2001). Certain vital rates such as adult hen survival, nest success rates, and juvenile recruitment drive sage-grouse population dynamics. Attempting to modify these vital rates to increase populations through either direct predator control actions or by manipulating habitat to indirectly control predation rates should be evaluated in terms of cost effectiveness and efficiency. The influence of weather patterns on these same vital rates should likewise be integrated into these discussions.
