Tonic Immobility in Sharks and Rays
Sharks and rays enter a trance-like state when their sensory pores on the nose are stimulated. This phenomenon is known as tonic immobility, or “trance.” Tonic immobility can occur naturally in these animals; however, it’s mostly induced by humans. This makes them more manageable during research projects involving sharks and rays of various species. Even though tonic immobility does not occur in all species of sharks, it still affects most types. In the Great White shark, its dorsal fin straightens and breathing slows down as well as muscle contractions become lax. For many animals that can experience this state, it is a survival strategy because looking dead to predators is useful sometimes for tricking them into letting their guard done long enough or altogether if they aren’t being too observant.
Tonic immobility in sharks for research
When researchers handle sharks, they often use tonic immobility to subdue them. Many scientists think that this is what occurs when the shark enters a trance-like state of relaxation and becomes deeply rhythmic in its breathing patterns. When gently turned on its back, its thought enters into this stage as an act of disorientation which relaxes the muscles and induces deep breathing rhythms without causing injury or struggle. Once released from these restraints, however, the shark will snap out of this daze within moments.
Scientists are still unsure why sharks enter tonic immobility. Some suggest it may be a defence strategy while others think that is related to mating behaviour, but nobody knows for sure at this point in time.