Berger+and+Gese+2007

Summary of Research on Coyote-Wolf Interference Competition

General Overview

  • Objective: Examine how interference competition with wolves (Canis lupus) affects the distribution and abundance of coyotes (Canis latrans).

  • Hypothesis: The presence of wolves limits coyote populations, influencing their range expansion following wolf extirpation in North America.

Methodology

  • Research Period: Data collected between August 2001 and August 2004 in Grand Teton National Park (GTNP), Wyoming.

  • Data Collection: Evaluated mortality, survival rates, and spatial dynamics of coyotes in both wolf-free and wolf-abundant sites.

  • Study Locations:

    • Wolf-Abundant Site: Elk Ranch, frequently utilized by wolves during denning (May-September) and winter.

    • Wolf-Free Site: Antelope Flats, not used by wolves.

  • Key Metrics: Coyote home-range overlap with wolves, dispersal rates of coyotes, and local population densities across the Greater Yellowstone Ecosystem (GYE).

Key Findings

Coyote Population Dynamics

  • Mean coyote densities vary significantly:

    • 33% lower in wolf-abundant sites in GTNP.

    • 39% decline in Yellowstone National Park after wolf reintroduction.

  • The statistical analysis showed a strong negative relationship between coyote and wolf densities (β = -3.988, P < 0.005, r² = 0.54).

Mortality and Survival Rates

  • Low overall mortality rate of coyotes due to wolves but 56% of transient coyote deaths were attributed to wolf predation.

  • Transient coyotes showed a 117% increase in dispersal rates in wolf-abundant areas compared to wolf-free areas.

  • Coyote survival estimates:

    • Resident coyotes had higher survival rates than transients (mean survival rates varied seasonally and by territorial status).

Competitive Interactions

  • Interference Competition: Findings support that wolves exert competitive pressure that limits coyote populations, especially for transient individuals who are less familiar with the landscape.

  • Notable Statistics:

    • Human-related fatalities constituted 45% of coyote mortality, with predation accounting for 30%.

    • Wolves were responsible for 83% of predation-related coyote deaths.

Spatial Dynamics

  • Home-range analysis revealed significant overlap:

    • Coyotes' home ranges were largely inside wolf territory.

    • Evidence of spatial segregation was minimal; however, transient coyotes exhibited higher dispersal metrics relative to permanent residents.

  • UDOI (Utilization Distribution Overlap Index) demonstrated a lower intensity of use even where overlap occurred.

Conclusions

  • The study confirms that wolves have a significant impact on coyote densities through competitive exclusion and predation, particularly affecting transient coyotes.

  • The relationship between the two species suggests localized population reductions rather than complete elimination of coyotes.

  • Human-related factors and environmental variations also play a critical role in shaping coyote populations.

Implications

  • Study emphasizes the complexity of interspecific relationships and suggests that while wolves limit coyote populations, they also provide opportunities for scavenging, which could affect coyote behavior and ecology.