Werewolf in the North Woods by Vicki Lewis Thompson

She caught him with his pants down…
When over-educated anthropology professor Roarke Wallace seeks to discredit her grandfather’s sighting of Bigfoot, Abby Winchell launches a counterattack. Sure, Grandpa Earl is dotty, but he’s not a liar. Taking his high-powered camera, she heads into the woods. No sign of Bigfoot, but she spots the learned professor…taking off his clothes and sprouting fur.
Painting Earl Dooley as a crackpot is the only way Roarke can prevent a media blitz that would endanger the Sasquatch and expose the local Were pack. He doesn’t count on Abby catching him on film. Or using the photos to blackmail him into taking her on his search for the Bigfoot pair. Roarke and Abby have every reason to distrust each other. But trekking through the woods strips away their preconceptions, revealing all the ways they’re…compatible.

But when the Were pack gets suspicious about Abby’s involvement, Roarke’s caught between loyalty to his kind, and loyalty to the woman he never expected to love…