Trancing

Trancing rabbits is the action of placing rabbits on their back to induce a paralysis known as tonic immobility or apparent death. The action is also known as the immobility response, hypnosis, or the freeze response.

Controversy
Contrary to popular belief, rabbits in a state of tonic immobility are not relaxed, hypnotized, or insensitive to pain. Scientists believe that this is a defense mechanism brought on when a rabbit has already been 'caught' by a predator. If the rabbit appears dead, the predator may release its grip momentarily and allows the rabbit to escape. Research has shown that rabbits in this state show an increased heart and respiratory rate with elevated plasma corticosterone levels, indicative of fear-induced stress.

The stress caused by this position can be fatal if rabbits are already suffering from respiratory and cardiovascular disease, and the sudden transition to from passive and active escape can be unpredictable and instantaneous which can result in significant injury to the rabbit.