VOICES Voices Icon Ideas and Insight From Explorers


Even Sharks Need a Little TLC

Workin’ 9 to 5 isn’t just for Dolly Parton and the rest of us humans—some wild critters also toil to eke out a living.

Take the selfless sycophants of the insect world, like the worker bees—which are possibly brainwashed into submission by their queens, as National Geographic News reported in 2007.

And of course there are the cleaner fish, which set up stations to scour visiting fish free of parasites–and get a meal in return. Like police and nurses, cleaner fish on coral reefs, for instance, also wear uniforms to advertise their “professions”—a tactic that also helps the fish avoid being eaten by their clients, I wrote last year.

Now a new study has investigated how cleaner wrasse and thresher sharks interact in a coastal seamount—or undersea mountain—in the Philippines.

Study leader Simon Oliver told me that the sharks will “slowly and systematically” swim over the areas where the fish set up shop, and eventually drop their tail fin—presumably a non-threatening way to invite the cleaner over.

The fish then begin “foraging” on the shark’s body, paying the most attention to its client’s parasite-rich fins and pelvis, said Oliver, of the University of Wales, Bangor.

Other shark species, such as gray reef sharks, will actually flare their mouths and gills to expose them to cleaner fish, as if to say, “I know I’m a big predator, [but] I’m not going to eat you, I promise,” Oliver said. (See shark pictures.)

My favorite finding is that cleaner fish work best in the morning (the opposite of me, who can’t seem to get going until 11 a.m.)

The PLoS ONE study says: “The gradual decline in the frequency of pelagic thresher shark cleaning events from morning until evening may be driven by hungry cleaners, which provide higher quality services early on in the day.”

Of course it’s always tempting to anthropomorphize animals. But lead author Simon also compared the cleaner-shark relationship to the way we interact with our doctors:

“Cleaning stations are like a surgery. Whereby you might visit your GP to relieve yourself of some ailment, it’s an essential part of [sharks’] life history, which relates directly to their health and hygiene,” he told me.

So, enough talk about work—it’s time to start the weekend!

Check out more weird coverage on National Geographic News.