BP's generally do not go on the offense and stalk down their prey out in open spaces. They are ambush predators who prefer to attack from their hides and tag unsuspecting prey in the environment they know every inch of. When hungry, at night you'll see them posted at the side of their hide's entrance with only their heat pits exposed.
Moving them to a foreign open air cage face-to-face with their prey cuts against the grain of everything they naturally prefer. They may be hungry enough to push through and eat in that context. But it's most likely causing unnecessary stress in an animal already prone to anxiety that cements negative feedback loop behavior.