By biologging three male and three female great whites off Mexico’s Guadalupe Island during 2017 and 2018 with cameras and activity- as well as telemetry-receivers to track speed, depth and the swimming direction of the sharks, a research team managed to gain vital insights into the group dynamics.
The tags also contained special receivers that were able to pick up movement of other sharks in close proximity which was vital to measure social interactions and behaviours between individuals. 30 additional sharks were fitted with acoustic transmitters between 2015 and 2017 and between 2017 and 2018, the research team tagged seven more individuals with acoustic transmitters.
The collected data for the study, called Social dynamics and individual hunting tactics of white sharks revealed by biologging, published in the journal Biology Letters, suggests that some sharks are more sociable than others. One individual which kept its tag on for a mere 30 hours, spent time with 12 other sharks, while another shark that was fitted with the tag for a total of five days, only decided to spend time with two other sharks.
The research team also noticed different hunting tactics with some individuals preferring shallow over deep waters and others hunting at night instead of during the day. The majority of socialising was recorded in close proximity to a group of seals, suggesting that the individuals form groups to take advantage of another shark’s hunting success.
“Seventy minutes is a long time to be swimming around with another white shark,” Yannis Papastamatiou, lead author of the study said in a statement.
“The important question we still have to answer is what’s the reason for being social for these sharks? We still don’t know, but it’s likely they may stay in proximity of other individuals in case those individuals are successful in killing large prey,” Papastamatiou said.
“They aren’t working together but being social could be a way to share information.”
To fully determine why the sharks are behaving like this, however, a larger study needs to be planned out, as the study points out: “While many associations were likely random, there was evidence of some stronger associations. Sharks varied in the depths they used and their activity, with some individuals more active in shallow water while others were more active 200–300 m deep. We propose that white sharks associate with other individuals so they can inadvertently share information on the location or remains of large prey. However, there may be a wide range of individual variability in both behaviour and sociality.”
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Photography courtesy of Cassandra Scott/Ocean Image Bank & Jayne Jenkins/Ocean Image Bank.