Disappearance Creek

From the back cover of Disappearance Creek:

Conducting wildlife surveys in a remote mountain wilderness east of Jackson Hole, Wyoming, wildlife biologist Whip Sawtell uncovers a series of mysterious disappearances. A pack of northern gray wolves vanished, then a small plane sent out by the government to look for the pack crashed without a trace. An elk hunter disappeared in the same area.

Sawtell follows the hunter's trail looking for his body, but instead finds a dead wolf, one shot from an airplane. Before Sawtell can leave the area a sniper pins him down behind a tree miles from a road. His ex-girlfriend, wolf biologist Cat Bonner, tracks Sawtell into the wilderness before he connects the dots.