Wolves, Cougars, Deer, and Fire
During the summer months, our fieldwork consists primarily of visiting wolf and cougar “GPS clusters,” or groups of GPS locations where a wolf or cougar may have eaten prey. We have been tracking collared cougars and wolves in our study areas since December 2016, documenting movements and examining kills and scavenging events. To learn more about how we investigate carnivore feeding sites, see our previous post titled “Why We Study Carnivores Using GPS Collars.”
Fires in 2017 and 2018 greatly impacted our ability to do fieldwork, and these fires altered the movement of our collared carnivores as well. The Okanogan study area centered around Twisp, WA has one of the highest rates of lightning strikes in the continental US. Combine this with dry conditions, daily winds, thick understory, and an abundance of Douglas-fir trees, and you have the perfect conditions for large-scale wildfires.
As a result of the fires, we had to suspend fieldwork operations for several weeks in both 2017 and 2018. Thanks to help from the US Forest Service, we were able to take down some cameras that were at the edges of new fire closure zones in 2017. I visited the fire camp and donned a shirt and pants made of Nomex, a fire-resistant clothing made of a nylon-like polymer. Some trail cameras put out across the study areas, meant to track wildlife in different habitat types, were burned in the fires of 2018. The Crescent Mountain Fire in particular was spreading rapidly in its first days due to prime fire conditions, so there was no safe way to rescue nearby research cameras and many were lost in the fire.
Over 60% of our Okanogan study area has burned due to natural or human-caused wildfires and prescribed burns since 1900. Fire affects food availability for deer, at first removing a lot of vegetation but later fostering nutritious new growth in the years after disturbance. These growth periods are known as “seral stages,” and we predict that they will have an impact on deer movement and survival. As a result, carnivores will also be affected by where food is available for deer post-fire. Fires can also change landscape structure, making an area more open. This might make it easier for cougars or wolves to spot deer, and fallen logs known as “blowdown” may make it harder for deer to escape these post-fire zones. Thus, disturbance events like fire might both benefit deer by providing forage and change predator-prey dynamics by altering hunting conditions for wolves and cougars.
Map of fires in the Okanogan (left) and Northeast (right) study areas going back to 1900. Brighter red colors are more recent fires, with faded tones indicating older fires. The 2017 Diamond Creek Fire and 2018 McLeod and Crescent Mountain Fires are in the brightest shades of red on the north and west boundaries of the Okanogan study area while the 2018 Boyds Fire can be seen on the northwest corner of the Northeast area.
To learn more about wildfires in the western USA, watch this talk by Paul Hessburg of the US Forest Service given at TEDxBend titled, “Why Wildfires Have Gotten Worse and What Can We Do About It?”
- Lauren Satterfield