Tonic immobility

Tonic immobility is a natural state of paralysis that animals enter, in most cases when presented with a threat.

Sharks can be placed in a tonic immobility state by inverting them. The shark remains in this state of paralysis for an average of fifteen minutes before it recovers. Scientists have exploited this phenomenon to study shark behaviour. Usually when being tested by scientists under this "tonic" state the scientists will put a chemical plume in the water awakening the shark.

Tonic immobility also can be somewhat effective on anole lizards and a loose study was done with tonic immobility with the rabbit. Both were inconsistent examples of tonic immobility.

Tonic immobility has also been used to describe the paralysis which often immobilizes animals such as rodents or birds when they feel threatened by a predator. It can be argued that tonic immobility plays a role in survival if it helps a hunted animal to blend in with its surroundings by remaining as motionless as an inanimate object. This tonic state is common with invertebrates as well.

Inducing tonic immobility in common animals requires, in some cases, extreme treatment such as electric shock along with other elements that produce stress.

Contrary to popular belief, theories regarding "putting a lobster to sleep" seem to be rumors without empirical data to confirm their validity.