Analyzing seasonal fluctuations in gopher distribution

Mazama pocket gophers are difficult to see, and most of us have never laid eyes on much less handled the actual animal. The cryptic nature of gophers poses particular problems for folks who are trying to count and assess the condition of current populations. Fortunately, gophers leave behind tell-tale signs of their presence; mounds. Though existence of mounds is an excellent method to determine where gophers occur on a particular landscape, a lack of mounds does not necessarily translate to lack of gophers. Seasonality, soil quality, and individual behavior can all interplay to determine the extent to which gophers will create mounds. CNLM biologists have been conducting seasonal gopher-mound surveys on Rainier Training Area prairies on Joint Base Lewis-McChord since summer 2015. These surveys can account for animals present but not detected from their mound building. These surveys also account for seasonal changes in mound-building activity.

Mazama pocket gophers rarely come to the surface, so their presence has to be detected by fresh mounds.

From these surveys a picture is beginning to emerge showing seasonal fluctuations in gopher occupancy. Occupancy decreased from summer to fall 2015 only to recover fully by the following summer. A similar pattern was observed in fall 2016, though the decrease was not as sharp as in 2015, presumably due to the wetter spring and summer. These surveys are part of a larger effort to assess impacts of prescribed fire on JBLM prairies, and CNLM biologists are currently investigating how burning may influence seasonal fluctuations in gopher occupancy. This information will better tailor prescribed fire rotations to maximize benefit for this threatened species.

Mazama pocket gopher mounds detected by the gopher survey team. Credit: Adam Martin.