Sharks take turns hunting by species, study says. Here’s reason for polite behavior

When it comes to hunting, sharks seem to exhibit a polite behavior, researchers say.

A half-dozen species of sharks off the coast of Florida have been observed taking turns searching for their next meal — a discovery that’s the first of its kind, according to a new study.

“This is a relatively rare way of sharing resources in nature, but it could be more common than we think in understudied marine ecosystems,” said Karissa Lear, a lead researcher of the study published Wednesday in The Royal Society, in a news release from Murdoch University’s Harry Butler Institute in Australia.

Lear and other researchers strapped FitBit-like devices on six shark species near Tampa Bay and analyzed 3,766 hours of data from 172 of them.

“We found bull sharks were most active in early morning hours, tiger sharks during midday, sandbar sharks during the afternoon, blacktip sharks during evening hours and both scalloped and great hammerhead sharks during nighttime hours, the only two species with substantial overlap in timing of peak activity,” Lear said.

So, are these sharks just really well-mannered? Not exactly.

The sharks are practicing something called “niche partitioning,” which allows species competing for the same resources to coexist, researchers say.

Niche partitioning can take several forms in nature, with species either specializing in different food, foraging or hunting in different areas, or rotating the time they hunt or forage.

The sharks in this study practiced the latter form, scientifically called “temporal partitioning.” Researchers say this is the first time marine predators have been observed partitioning resources by searching for food at different times of the day.

“This both reduced the competition for food and, for some species, reduces the chances of being preyed upon by larger species,” Adrian Gleiss, another lead researcher, said in the news release.

The larger and more dominant species — the tiger, bull and great hammerhead sharks — hunted at times of the day that perhaps suited them best, researchers say.

For example, researchers say hammerhead sharks have “superior binocular vision,” putting them at an advantage at night, while tiger sharks are believed to use silhouettes of prey to hunt, a tactic that requires more light.

Meanwhile, smaller species like blacktip sharks may change their feeding time to avoid run-ins with larger sharks.

Marine predators, including sharks, are important to healthy ecosystems, researchers say.

“Understanding the mechanisms that allow marine predators to coexist will help us to preserve and restore healthy, predator-rich marine systems,” Lear said.

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