The researchers exposed Port Jackson Sharks to two different stimuli - air bubbles and an underwater LED. Each stimulus was activated prior to the release of a food reward and the response of the shark post-stimulus was recorded.
Sharks which were exposed to the air-bubble stimulus showed a reduction in the time taken to react to the stimulus, in anticipation of a food reward. Response behaviours included biting or vigorous respiratory pumping such as would be observed when searching for buried prey in the wild.
The group which was exposed to the LED stimulus showed no modified behaviour towards the stimulus suggesting no anticipation of reward. This could be owing to the fact that, as nocturnal predators, Port Jackson sharks do not rely on vision for prey detection and capture and therefore the LED stimulus was unable to elicit a response.
Owing to the fact that there was a period of 24 hours between trials, the Port Jackson sharks were able to retain memories of the association between the stimulus and reward for at least 24 hours and one of the sharks even remembered the association for 40 days.
Port Jackson sharks are an excellent model species for this study as they are reef associated and have been shown to return to the same point on the reef up to 24 hours later after being displaced. This suggests that they must have some capacity for spatial memory.
This study demonstrates, for the first time, the learning capabilities of a benthic elasmobranch. Of all shark species, benthic sharks are the group with the smallest brains; previous studies on teleost fish have demonstrated a link between brain size and cognitive ability and therefore the researchers surmise that our understanding of cognitive ability in sharks in greatly lacking.
Guttridge, T. and Brown, C. (2014) Learning and memory in the Port Jackson shark, Heterodontus
portusjacksoni. Animal Cognition (17): 415-425
Sharks which were exposed to the air-bubble stimulus showed a reduction in the time taken to react to the stimulus, in anticipation of a food reward. Response behaviours included biting or vigorous respiratory pumping such as would be observed when searching for buried prey in the wild.
The group which was exposed to the LED stimulus showed no modified behaviour towards the stimulus suggesting no anticipation of reward. This could be owing to the fact that, as nocturnal predators, Port Jackson sharks do not rely on vision for prey detection and capture and therefore the LED stimulus was unable to elicit a response.
Owing to the fact that there was a period of 24 hours between trials, the Port Jackson sharks were able to retain memories of the association between the stimulus and reward for at least 24 hours and one of the sharks even remembered the association for 40 days.
Port Jackson sharks are an excellent model species for this study as they are reef associated and have been shown to return to the same point on the reef up to 24 hours later after being displaced. This suggests that they must have some capacity for spatial memory.
This study demonstrates, for the first time, the learning capabilities of a benthic elasmobranch. Of all shark species, benthic sharks are the group with the smallest brains; previous studies on teleost fish have demonstrated a link between brain size and cognitive ability and therefore the researchers surmise that our understanding of cognitive ability in sharks in greatly lacking.
Guttridge, T. and Brown, C. (2014) Learning and memory in the Port Jackson shark, Heterodontus
portusjacksoni. Animal Cognition (17): 415-425
