Sightings of white sharks (Carcharodon carcharias) have crashed this year in False Bay near Cape Town, South Africa—one of the best-known hot spots of the predators in the world—and scientists aren’t sure why. Orcas, which love to dine on shark liver, may have scared them off, researchers say, but human activities could also play a role.
Shark Spotters, a local charity that monitors the city’s beaches daily and warns swimmers if sharks are near, has not recorded a single confirmed white shark sighting this year—not even during the summer months, from January to April, when the fish usually come close to shore.
The boats that take tourists to watch sharks hunt seals at Seal Island, in the middle of False Bay, have not recorded sightings either. Sharks tagged along the South African coast have not “pinged” any of the receivers located in the bay since January 2017, and white shark bite marks have been missing from whale carcasses floating in the bay this year.
The absence is unprecedented in Shark Spotters’ 16-year history, says the charity’s research manager, Tamlyn Engelbrecht. Usually, there are more than 200 sightings each year; the number has never been zero.
One possibility is that sharks are on the run from even bigger predators. Data show that white shark sightings have dropped significantly in False Bay since 2015 when two orcas (Orcinus orca)—nicknamed Starboard and Port because their dorsal fins curl opposite ways—started to predate on a local colony of sevengill sharks (Notorynchus cepedianus).
- Read the full article at Science Mag.