Grey reef sharks are changing their habits as ocean temperatures rise. These sharks usually stick close to coral reefs, but they’re starting to move away when the water gets too warm.
Scientists tracked over 120 sharks using special tags and underwater microphones. They watched the sharks from 2013 to 2020 in the Indian Ocean.
When the water heats up, it can harm coral reefs. This process is called coral bleaching.
During these times, sharks spend less time near the reefs. They swim to other areas more often and stay away longer.
After a big warming event in 2015-2016, some sharks kept this new behavior for up to 16 months.
Climate change is making these warm spells happen more often. By 2043, scientists think coral reefs might face yearly stress from heat. This could mean big changes for shark populations and the reefs they call home.
Sharks face a tough choice when reefs get too warm. They can:
- Stay put and deal with the heat
- Swim to cooler, deeper waters
Many seem to pick option 2. This choice uses more energy but keeps them cooler.
Shark movement has a big impact on reef health. These predators help keep the food chain balanced. They also bring nutrients from deep waters to the reefs.
If sharks leave, it could make it harder for reefs to bounce back from stress.
Not all reefs are losing their sharks, though. Some spots actually saw more sharks during the study. This hints that some reefs might handle heat better than others.
Scientists aren’t sure why yet, but they have some guesses:
- Some islands have lots of seabirds
- Seabirds poop adds nutrients to the water
- More nutrients might mean more fish
- More fish could keep sharks around
The ocean is a complex place. As it warms, animals like sharks have to adapt. Their choices ripple through the whole ecosystem.
Scientists are working hard to understand these changes and what they mean for the future of our oceans.