Shark in Shifts: Study Explains Why Different Species Take Turns Hunting

While sharks have earned a reputation for being one of the most ferocious hunters in the water, they actually have a unique behavior - they wait for their turn.

Researchers from the Harry Butler Institute at Murdoch University discovered the unusual behavior after strapping monitors to six different shark species near Tampa Bay, Florida. They discovered that sharks adhere to their respective "shifts," based on their species - marking discovery that's the first of its kind in the process.

Details of the groundbreaking study are presented in the journal Proceedings of the Royal Society B, in the report titled "Temporal niche partitioning as a novel mechanism promoting co-existence of sympatric predators in marine systems."

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Niche Partitioning Observed in Sharks

The sharing between animals may be time, resources, or even space, called niche partitioning. An entry from the Encyclopedia of Biodiversity explains how it is a key component that allows often competing and predatory animals to survive. However, the researchers explain in their paper that this phenomenon is poorly explored and documented among marine animals due to the difficulty of monitoring the mobile underwater animals.

After monitoring about 172 specimens across six different shark species near Tampa Bay, researchers analyzed more than 3,700 hours of data and made a fascinating discovery: that sharks had shifts hunting in the waters. Basically, bull sharks were active during the early morning hours, followed by tiger sharks in the midday. By the afternoon, sandbar sharks are most active, followed by blacktip sharks in the evening. By nighttime, researchers report the only instance of shark species sharing the schedule with scalloped and great hammerhead sharks active at almost the same time.

While it appears like a mutual agreement between the sharks, it's actually a case of niche partitioning. Other animals are usually limited to a certain slice of the hunting ground or are limited to hunting specific prey. In the shark's case, they share the resources by having each species adhere to a certain time of the day, which makes it look like they each have their shifts. The form of niche partitioning observed by the Murdoch University researchers is technically called "temporal partitioning," which is observed in marine predators.

Works for Everyone, Both Large and Small Sharks

In a press release from Murdoch University, co-lead researcher Adrian Gleiss explains that niche partitioning reduced the competition for food. Additionally, for some species, it reduces the odds of being hunted by other, larger species. It explains why the larger and more dominant species - the tiger, bull, and great hammerhead sharks - all tend to hunt during the times of the day that best suits their capabilities. Specifically, hammerhead sharks have a "superior binocular vision" that gives them an edge during the night. On the other hand, tiger sharks are generally believed to use the silhouette of their prey in tracking and hunting, a feat that requires an ample amount of light.

On the other hand, other smaller species like blacktip sharks probably adopt their feeding time to avoid larger sharks. Researchers also took the opportunity to stress the importance of marine predators like sharks in keeping healthy ecosystems.