What is the primary reason the Handler believes the dog was lost?

The Handler believes the dog was lost primarily because it was eaten by a panther. This conclusion likely stems from the context surrounding the situation, indicating a plausible and perhaps threatening scenario that could have led to the dog's disappearance. Considering the environment typically inhabited by panthers, the Handler's reasoning reflects a realistic concern about predators in the area. This perspective emphasizes the potential dangers that wild animals pose to domestic pets, providing a logical explanation for the loss of the dog in a way that resonates with the Handler's understanding of the natural dynamics at play in that specific setting.