In Focus: Oxpeckers
Like a bevy of beauticians, yellow-billed oxpeckers line up to remove, deftly, engorged ticks and biting insects from the neck of a Maasai giraffe. One spots a passing fly and takes off to snatch it, beating the others to the prize. Scenes like this in Kenya’s Maasai Mara were long held up as a textbook example of mutualism, in which two species work together for shared benefit. The oxpeckers have stout, flattened bills for scissoring through the fur of their hosts – which also include African buffalo, rhino, zebra and antelopes – as well as long claws for holding on. Meanwhile, the herbivores benefit by being rid of troublesome parasites. But then closer study revealed that the birds were also sneaking meals of blood from the bites, making wounds worse, and that their feeding actually had no impact on the overall number of ticks, fleas or flies. So the relationship between oxpecker and mammal is not purely mutualism: sometimes the birds are themselves parasites. Their services do not come without a cost.