Shark Tonic Immobility
This project aims to address major gaps in our understanding of the phenomenon of tonic immobility or “death feigning”.
Tonic Immobility is a type of unlearned behavioural response characterized by a state of torpor. It has been considered as a defence mechanism against predators that is shared by animals such as fish, mammals, reptiles, birds and insects. However, given the habitat and known predators of sharks it does not seem likely that it would serve as an anti-predator strategy. Evidence seems to suggest that tonic immobility may play a role in the reproductive behaviour of some sharks.
However, the biological significance of the response in elasmobranchs remains uncertain. When looking specifically at mating, males subject females to tonic immobility, but if tonic was evolutionary related to mating, then females should be more susceptible to tonic immobility than males. Then why then males are also prone to it?
This project will look at species specific and gender specific responses to tonic immobility in two species of endemic catsharks: the puffadder shyshark (Haploblepharus edwardsii) and dark shyshark (Haploblepharus pictus).