Jungle Rapture by M.A. Jewell

An advocate for endangered species, journalist Kelsi Gorman travels to the Brazilian Amazon to locate a mysterious black jaguar the size of a saber-toothed tiger. Instead, the enormous cat finds her knee deep in mud, blood, and smugglers. Jaime Salazar, one of a few surviving male jaguar shifters, encounters a scent he never thought to find—a female jag shifter.

Jag queens exist only in the elder’s stories, but someone staked out a she-cat like poacher bait. In a fit of primal instinct, Jaime marks Kelsi as his mate. Now, no other female will arouse him. To avoid a long celibate life, he is forced to woo his reluctant mate-to-be. But first he must keep her alive.