Relax Immobility
in sharks: preliminary results on Caribbean reef sharks.
Sturla Avogadri Riccardo and Gioelli
Fabrizio.
Shark Academy -
via monte Ortobene, 2 07020 Porto San Paolo (OT) Italy.
corresponding authors: e-mail:
riccardosturla@sharkacademy.com -
fabrizio@sharkacademy.com
Immobilization of sharks for husbandry, medical cures and research
purposes currently relies on Tonic immobility techniques, that consist in rolling the
shark onto his back and are often associated with use of hooks. A more recent technique,
applied for tourist entertainment, allows to immobilize sharks performing massage on their
snout. This manipulation induces in sharks a trance-like state, thus the name Trance
immobility. Both techniques, Tonic and Trance immobility, relies upon shark feeding and
induce in sharks an uncosciousness state, that allows manipulation by researchers. In the
present study a Caribbean reef shark (Carcharhinus perezi) was approached without feeding
and handled without inducing unconsciousness. Several Caribbean reef sharks were
approached in Grand Bahama waters applying a technique named "shark pretending":
the researcher ("pretender") standed on the sea bottom and offered food to
sharks with a sequence of predetermined movements, according to shark approach direction.
Once a shark was close enough, the pretender hid food and grabbed shark's head, performing
massage on its snout by thumb circular movements. Some individuals responded positively
and one female showed a very peculiar behaviour: following the manipulation, the shark
became relaxed without losing consciousness, thus the new name Relax immobility, and let
the pretender remove parasites from its dorsal fin. Suprisingly, after this first
experience, the same individual went spontaneously and repeatedly back to the pretender,
without food attraction, and approached the same pretender also one day later, suggesting
memory capacity and learning behaviour. Results obtained in these preliminary studies
encourage further trials on more individuals.
KEYWORDS: Shark pretending, Relax immobility, learning behaviour.
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