In 2016, when a howling Hurricane Matthew ripped across the northern Bahamas, the tiger sharks cruising around Little Bahama Bank did something unusual: they stayed put.
Winds topped 140 mph as the storm crossed the bank, churning up sands, rocks and presumably wildlife in the shallow water.
‘We're talking 12, 15-feet depth and some of these sharks are 15 feet. There's a lot of wind pushing through that's going to move a lot of debris. That can't be very enjoyable,” said Neil Hammerschlag, director of shark research and conservation at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. “I assume they would evacuate, based on what I would do and also what sharks have done from previous studies.”
But the tiger sharks, he said, “didn’t even seem to flinch.”
In fact, a year later when Hurricane Irma swept across Florida with much slower winds over Biscayne Bay, other sharks Hammerschlag monitors — including greater hammerheads, nurse sharks, and bull sharks — all fled.
So what’s the difference? Hammerschlag, who co-authored a study published this month in the journal Estuarine, Coastal and Shelf Science, thinks it may have to do with how tiger sharks are built.
“They’re built like tanks,” he said. “They're robust, they're strong, and they don't get stressed out. If they're not getting too stressed out, then why flee? Why evacuate if it's going to take energy and time?”
Powerful storms that can be lethal to other wildlife also leave behind food for sharks, which might also factor into why tiger sharks stay. Following Hurricane Matthew, Hammerschlag said the number of tiger sharks actually doubled.
”When it comes to scavenging afterwards, remember, there’s going to be competition among other tiger sharks,” he said. “It's always good to be the first in line at the buffet than the last in line at the buffet.”
With climate change expected to produce more intense hurricanes, Hammerschlag said it’s important to understand how that plays out differently among wildlife. Changing the balance of an ecosystem, especially with a big, apex predator like a tiger shark, can have implications down the food chain, he said.
Sharks that stay in storm-damaged areas may provide a benefit after a storm. Likewise, he said, when sharks flee — as was the case in Biscayne Bay after Irma — there can be costs.
“There are these species-specific differences and we can't just make broad generalizations,” he said. “If these animals for some reason alter their distributions, there might be altered ecosystem changes or dynamics that result.”
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