Interspecific interactions between sympatric carnivores

Interspecific competition between predators can be a driving force in community ecology.  Based on the current availability of restoration efforts of predators, broad-scaled analyses have been conducted, mainly focusing on the top-down effects of top predators on prey.  Less emphasized are studies on the influence of predators on other predator populations, even though these interactions have been hypothesized to significantly affect ecosystem function.  Furthermore, understanding how top predator restoration effects a suite of other species is very important for predicting the outcome of these efforts and developing an idea of the positive and negative impacts of these projects.

Unfortunately, many of the questions involved in understanding these processes require behavioral data that are quite difficult to obtain.  Luckily, Yellowstone National Park provides a unique opportunity to observe wolves interacting with other predators such as coyotes.  The northern part of the park is mostly grassland, and viewing these animals is relatively easy compared to other forested ecosystems.  Since the translocation of wolves into Yellowstone in 1996-1996, the wolf management team has been noting interactions between wolves and coyotes.  We analyzed these interactions to describe some of the basic characteristics of wolf-coyote interactions, which have rarely been seen where the two species coexist.

We found that the majority (75%) of interactions occurred at ungulate-carcass sites. Wolves initiated the majority of encounters (85%), generally outnumbered coyotes (39%), and dominated (91%) most interactions. Wolves typically (79%) chased coyotes without physical contact; however, 25 interactions (7%) resulted in a coyote death. Interactions decreased over time, suggesting coyote adaptation or a decline in coyote density. In the majority (80%) of fatal interactions, wolves outnumbered coyotes. However, wolves did not outnumber coyotes in interactions (n = 18) where coyotes chased or attacked/harassed wolves. Our results suggest that wolves are the dominant canid, group size may influence the outcome of interactions, and coyotes must benefit from the access to carrion at wolf-killed carcasses (Merkle et al. 2009).

Collaborators: National Parks Service, Doug Smith, Dan Stahler