Although Meekan has studied whale sharks since 1996, they still surprise him. For years, researchers believed these filter feeders only consumed microscopic sea life and small fish, but it turns out a recent study led by Meekan recently revealed they eat seaweed, too. These record-breaking fish are now also considered the world’s largest omnivores.
Some other mysteries of whale sharks may soon be uncovered around Mafia Island, Zanzibar’s lesser-known neighbor. The Mafia archipelago, southeast of Tanzania’s capital, Dar es Salaam, is made up of five islands—Mafia is the biggest, then there’s Bwejuu, Chole, Jibondo, and Juani. Scientists who have tagged whale sharks and tracked their mobility over the years say the ones around Mafia Island don’t wander too far from the area.
Because the whale sharks observed at Mafia Island are rarely seen elsewhere, researchers can keep better tabs on individuals to identify more precisely the elements that cause them harm. Injuries occur through fishing (due to fishermen trying to catch other targets) and collisions with boats. Some fishermen have also hunted whale sharks for their meat, fins, or oil, which halved their worldwide population within 75 years of the last century.
Although there aren’t enforceable interaction regulations in Mafia Island, Chris Rohner, Principal Scientist at the Marine Megafauna Foundation, said tour operators still try to abide by industry recommendations. “As a guest, you have some power over how the trip goes. Make sure to mention that it is important to you to have a responsible encounter, even if this means missing out on a swim when other people are already swimming with a particular shark,” says Rohner. “The best encounters are those where the shark and the tourists are both happy. This is not difficult—whale sharks are really chill and, off Mafia, they are mostly just interested in eating lots of plankton.”
Visitors to Tanzania can book trips with leading scientists in whale shark research through the Marine Megafauna Foundation or with responsible tour operator Kitu Kiblu.
When to go: October to February