FLORIDA — Great white sharks around Mexico’s Guadalupe Island sometimes hang out with each other — and while it’s not a popularity contest, some might just be a little more social than the rest.
Florida International University (FIU) marine scientist Yannis Papastamatiou and a collaborative team of researchers wanted to uncover some of the mysteries of the white sharks that gather seasonally around Guadalupe Island.
They found sharks tended to stick together when patrolling for food.
“Most associations were short, but there were sharks where we found considerably longer associations, much more likely to be social associations,” said Papastamatiou, lead author of the study.
“Seventy minutes is a long time to be swimming around with another white shark.”
Normally, studying such cryptic animals involves some form of tracking device. To study these white sharks, though, the researchers needed a much better tag.
They combined different commercially available technology into a “super social tag” equipped with a video camera and an array of sensors tracking acceleration, depth, direction and more. What put the “social” in this tag was special receivers that could detect other tagged sharks nearby.
Those other tagged sharks were the result of previous work the study’s co-author Mauricio Hoyos-Padilla had done to track movements of white sharks around Guadalupe Island. Around 30 to 37 of those sharks showed up on another white shark’s super social tags.
Six white sharks over a four-year period were tagged. Data shows they prefer to be in groups with members of the same sex.
If the sharks shared any other similarities, it was in how totally unique each one was. One shark that kept its tag on for only 30 hours had among the highest number of associations — 12 sharks. Another shark had the tag on for five days but only spent time with two other sharks.
They also displayed different hunting tactics. Some were active in shallow waters, others at greater depths. Some were more active during the day, others at night.
The challenge of the hunt was reflected in the video footage. A great white followed a turtle. Then, the turtle saw it and got away. A great white followed a sea lion.
The sea lion spotted it, danced loops around the shark, and got away. Papastamatiou points out this isn’t unique to white sharks, since predators are unsuccessful a lot of the time.
That’s why forming social associations might be so important. Papastamatiou has studied the social lives of other shark species and noticed a link between sociality and the ability to take advantage of another shark’s hunting success. The same thing may be happening at Guadalupe Island.
“Technology now can open up the secret lives of these animals,” Papastamatiou said.
The findings were the cover story of Biology Letters.
