Published: May 2007
Did You Know?
In Did You Know? the National Geographic magazine team shares extra information we gathered to expand your knowledge of our featured subjects.

Numerous species of birds, including sandpipers, wagtails, and oxpeckers, have been seen riding the backs of hippos. Some of these birds use hippos as a mobile perch for fishing, whereas others feed on the parasitic leeches and ticks that regularly inhabit hippos' hides. As birds feed on these parasites, it's possible that the birds remove dead and infected tissue from cuts and wounds, which result from the frequent fights within the herd. By foraging for parasites, the birds may be helping the hippos heal, but the link is still unclear.

—Heidi Schultz