Methods

Cougar Capture

We use trained hounds to track and tree cougars, therefore cougar capture is heavily dependent on fresh snowfall to locate fresh cougar tracks and occurs primarily during the winter months. We typically spend 3-4 days per week looking for tracks along roads.

Treed cougars are immobilized with a remotely administered mixture of ketamine and xylazine. Upon immobilization cougars are weighed, sexed, and aged. Prior to being released, cougars are fitted with either a GPS collar or a standard VHF radio-collar equipped with a mortality sensor. In addition, cougars are fitted with two permanent, plastic ear tags that have a unique ID number.

Wolf Capture

We use rubber-jawed leg-hold traps in the spring and fall to trap wolves along roads and trails. In the winter, a helicopter may be used to replace collars near the end of their battery life or to place additional collars in a pack. We immobilize captured wolves with Telazol. Wolves are sexed, weighed, and aged before being fit with a GPS collar. Captured wolves are then released on site to rejoin their packs.

Identifying Potential Predation Sites

Our GPS collars deployed on cougar are scheduled to obtain 8 locations per day. We remotely download location data from GPS collars every 2-3 weeks. Location data are run through computer software to identify "clusters" of locations. For cougar, we define a cluster as an area where there are at least 2 locations within 200m of each other over a six day window. Cluster locations are plotted on 1:24k USGS topographic maps and are later visited by field crews.

Because wolves travel in packs (versus a solitary cougar), have reduced prey handling times (a pack takes less time to consume prey once it is acquired), and have seasonal restrictions to their movements (denning), the criteria for identifying a potential predation site is different for wolves and cougar. Our GPS collars deployed on wolves are scheduled to obtain 8 locations per day throughout the year, but for two weeks in June and July collars are programmed to obtain locations every 30 minutes. This high intensity of location fixes through a reduced interval schedule allow us to account for the reduced time it takes a pack of 4-5 wolves to handle a prey item in the summer. In the winter, wolves generally travel together as a pack and spend more time at carcasses so prey handling time is longer and the 3-hour interval is sufficient to identify potential predation sites. We define a wolf cluster as an area where there are at least 2 locations within 300m of each other over a four day window. Similar to location data for cougar, we remotely download wolf GPS collars every 2-3 weeks, generate location clusters, and have field crews visit these sites to look for prey remains.

Searching Potential Predation Sites

After identifying "clusters" from location data for wolves and cougar, we load the coordinates for the clusters onto handheld GPS units. We systematically search the area surrounding the cluster center to look for prey remains. If prey remains are located, we determine the species, age, sex, and physical condition of the prey item that was acquired.