Sharks respond to hurricanes in different ways based on their species and location, according to a new study from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science. The researchers found that large tiger sharks, in particular, choose not to evacuate before a storm, but instead prepare to feast on other animals that perish.
The experts tracked large sharks in Miami and The Bahamas to investigate how these migratory animals behave in the face of hurricanes and other major storms.
The researchers analyzed acoustic tag data from tiger sharks, bull sharks, nurse sharks, and great hammerheads before, during, and after Hurricane Matthew in 2016 and Hurricane Irma in 2017.
The team investigated whether sharks evacuated shallow coastal habitat during the hurricanes, as has been previously found for smaller sharks elsewhere.
“Located on the northwest edge of the Little Bahama Bank, Bahamas, an acoustic array consisting of 32 acoustic telemetry receivers tracking tiger sharks sustained a direct hit from Hurricane Matthew in 2016,” explained the study authors. “Daily detections of tagged tiger sharks within the array were consistent before and during the hurricane.”
The tiger sharks remained in shallow inshore waters, even as the site received a direct hit from the eye of the category-5 Hurricane Matthew. Immediately after the storm, the number of tiger sharks doubled.
In Biscayne Bay, an array of 32 acoustic receivers tracked bull sharks, nurse sharks, and great hammerhead sharks during Hurricane Irma in 2017. Nearly all of the sharks, with the exception of two nurse sharks, evacuated the shallow waters and could no longer be detected.
“I was amazed to see that big tiger sharks didn’t evacuate even as the eye of the hurricane was bearing down on them, it was as if they didn’t even flinch,” said Professor Neil Hammerschlag.
“Their numbers even increased after the storm passed. We suspect tiger sharks were probably taking advantage of all the new scavenging opportunities from dead animals that were churned up in the storm.”
The researchers noted that global climate change is expected to increase the strength and frequency of storm events.
“Although aquatic animals can be affected by acute natural disturbances, information on the immediate consequences of these weather systems on the behavioral ecology of highly mobile aquatic predators remains limited.”
According to Professor Hammerschlag, how these storms impact the environment, including large sharks, is of interest and conservation concern to many.
The study is published in the journal Estuarine, Coastal and Shelf Science.