National Wildlife Research Center (NWRC)

PROJECT GOAL: Improve current knowledge of predator ecology, physiology, and behavior relative to depredations on species of human concern, and assess predator responses to management practices, and develop control aproaches that effectively target alpha coyotes.

Project Accomplishments 2008

Do Wolves Limit the Distribution and Abundance of Coyotes?—Scientists at the NWRC field station in Logan, Utah, are investigating whether competition from wolves limits the distribution and abundance of coyotes, and whether the elimination of wolves from certain areas has resulted in the coyote range expansion throughout much of North America.  The scientists analyzed spatial, seasonal, and temporal variation in wolf distribution and abundance to test the hypothesis that competition with wolves limits the distribution and abundance of coyotes.  From 2001 to 2004, the researchers gathered data on cause-specific mortality and survival rates of coyotes captured at wolf-free and wolf-abundant sites in Grand Teton National Park (GTNP) in Wyoming to determine whether mortality due to wolves is sufficient to reduce coyote densities.  They also examined whether spatial segregation limits the local distribution of coyotes by evaluating home-range overlap between resident coyotes and wolves, and by contrasting dispersal rates of transient coyotes captured in wolf-free and wolf-abundant areas.  Finally, they analyzed data on population densities of both species at three study areas across the Greater Yellowstone Ecosystem (GYE) to determine whether coyotes were less abundant where wolves were common. 

Although coyotes were the numerically dominant predator across the GYE, densities varied spatially and temporally in accordance with wolf abundance.  Mean coyote densities were 33% lower at wolf-abundant sites in GTNP, and densities declined 39% in Yellowstone National Park following wolf reintroduction.  A strong negative relationship between coyote and wolf densities, both within and across study sites, supports the hypothesis that competition with wolves limits coyote populations.  Overall mortality of coyotes resulting from wolf predation was low, but wolves were responsible for 56% of transient coyote deaths.  In addition, dispersal rates of transient coyotes captured at wolf-abundant sites were 117% higher than for transients captured in wolf-free areas.  The scientists concluded that coyote abundance is limited by competition with wolves, and that differential effects on survival and dispersal rates of transient coyotes are important mechanisms by which wolves reduce coyote densities.

Coyote Scavenging Ecology and Recolonizing Wolves in Montana’s Madison Range—Inference from studies of competition between species can be constrained where competitors have occupied the same area for long periods and little change in behavior is evident.  Fortunately, wolf recolonization of the GYE provides a rare opportunity to identify new behaviors facilitating coexistence between species of canids.  Accordingly, NWRC scientists in Logan, Utah, investigated behavioral interactions between putatively naïve coyotes and recolonizing wolves at ungulate carcasses in Montana’s Madison range.  The scientists employed a quasi-experimental study design consisting of a 3–level carcass treatment (actual wolf presence, simulated wolf presence, wolf absence) to assess factors influencing coyote risk assessment, carrion consumption, and aggressive encounters with wolves.

Socially dominant coyotes (alphas and betas) responded to actual and simulated wolf presence by increasing the proportion of time spent vigilant while scavenging.  Vigilance behavior was more pronounced when scavenging closer to protective cover, where visual obstacles inhibited the ability of coyotes to scan for, and possibly escape from, returning wolves.  Despite greater time spent vigilant, alpha coyotes consumed the greatest amount of carrion biomass.  This was accomplished by feeding on carcasses in earlier stages of consumption when organs and large muscle tissues were still present.  This suggests that alpha coyotes might trade-off greater risk for higher quality food items.  Coyotes aggressively confronted wolves.  Numeric superiority of coyotes and the stage of carcass consumption were influential in determining whether coyotes were able to displace wolves from carcasses.  Coyotes relied on a gradient of risk-sensitive behaviors, ranging from elevated vigilance to aggressive confrontation, to manage risk associated with wolf presence.  Identification of these behaviors and their sensitivity to numeric and social factors are important steps in elucidating mechanisms that allow social canids to occupy the same area.

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Logan, UT, Field Station