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Study shows sharks aren’t deterred by urban beaches, upping risk of human encounters

Nurse sharks feed on pieces of squid in the research lab of Aaron LeBeau, associate professor in the Department of Pathology and Laboratory Medicine at the University of Wisconsin-Madison on December 15, 2021. (Photo by Bryce Richter / UW-Madison)

A study conducted at the University of Miami shows that sharks are attracted to urban areas, promoting interactions between sharks and humans.

“We predicted sharks would exhibit avoidance behaviors of areas close to Miami,” the study, titled “Urban Sharks: Residency patterns of marine top predators in relation to a coastal metropolis,” reads. “However, we did not find empirical support for these predictions.”

Instead, researchers found that the ocean predators are “urban adapters,” meaning that while they spend much of their time in natural waters, they are comfortable approaching areas populated by humans.

“Modeling also revealed that an unmeasured spatial variable was driving considerable shark residency in areas exposed to high urbanization,” wrote researchers.

The study examined the space use of 14 great hammerheads, 13 bull sharks and 25 nurse sharks, all of which showed a similar level of comfort with urbanized beaches.

The authors of the study hypothesize that factors like food provision, including the discarding of fish carcasses, might be at play in shark attraction to urbanized areas.

This behavior differs from most land predators, which generally stay far away from urban areas due to things like chemicals, light and noise pollution.

“Few studies have investigated the movements of ocean predators in relation to urbanization, but since other studies have shown that land predators are urban avoiders, we expected sharks to be too,” said UM Shark Research and Conservation Program Director Neil Hammerschlag, the lead author of the study. “We were surprised to find that the sharks we tracked spent so much time near the lights and sounds of the busy city, often close to shore, no matter the time of day.”

Hammerschlag said that sharks are “at risk of exposure to toxic pollutants as well as fishing” by spending so much time close to shore, as well as that there could be some risk of negative human-shark encounters.

The study identified areas of the Miami shore that people may want to avoid in case of encounters with sharks.

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