Cage diving has proven to be an important sustainable practice in ecotourism when it comes to great white sharks (Carcharodon carcharias). But not much is known about the sharks’ behaviour during this activity.
In a study, which monitored the surface behaviour of white sharks during cage-diving activities around Guadalupe Island in Mexico, researchers observed a variety of behaviours as well as the role of an individual shark’s length and maturity on whether or not it caught the bait offered during these encounters. The relative size of sharks also played an important part in social interactions between individuals, with smaller sharks giving way to larger ones, even if the smaller shark arrived first on the scene.
During a total of 87 days on-board six cage-diving boats in 2012-2014, the surface behaviour of 106 white sharks was recorded. Most of the observed sharks were young (63%), with 37% considered mature. The majority of sharks were male (71%).
A range of behaviours
Researchers classified the sharks’ interactions into 11 behaviours, including parading, close inspection, horizontal attack, vertical attack, bait catching, feeding, not feeding, buoy catching, encounter, escape, and staying. Mature males tended to do more parading, close inspections and horizontal attacks, while immature females tended to do more vertical attacks. But there was no difference in behaviour between older and younger males.
Scientists found the sharks displayed a simple stimulus-response reflex, a pattern related to feeding, and warned that intentional feeding of individual sharks should be avoided to prevent white sharks from being conditioned to boats, possibly leading to negative impacts on ecotourism.
This study was the first ethological analysis of the behaviour of white sharks in Guadalupe as they aggregated in the open ocean. The study devised a standardized method for the study of white sharks in baiting situations, which could be applied to other locations.
As white sharks are a vulnerable species, the researchers suggested that more studies of this kind could help improve the monitoring, management and conservation of the sharks.