Why are Cape fur seals in South Africa infected with rabies?

It’s the world’s first significant rabies infection in marine mammals. And it has scientists – and beachgoers – worried.

In May this year, a seal at a popular beach in Cape Town, South Africa, bit five surfers in a matter of minutes. The surfers laughed it off with characteristic nonchalance, but seal experts were concerned because this extremely unusual behaviour seemed part of what was becoming a pattern.

Six days earlier, on the other side of the city, a seal had washed up with horrific facial injuries that could only have been caused by a seriously aggressive animal.

Starting in late 2021, authorities noted with concern an uptick in seal aggression. While most seals continued to ignore people, a few seemingly “deranged” animals had started biting people or other animals with no provocation.

“Although the behaviour looked ‘rabid’, our best scientific knowledge was that seals don’t get rabies,” says Dr Tess Gridley, founding director of Sea Search, an NGO specialising in marine mammal research.

After the May attacks, as public speculation spiked, a decision was made to send four seals (the two previously mentioned and two others) for rabies testing. “We were desperately hoping it wouldn’t be rabies,” says Gridley.