The relationship between oxpeckers and the large mammals from which they pick ticks is a complex one. It was long thought to be a straightforward case of mutual benefit, until it was realised that the birds also open wounds and drink their hosts’ blood, suggesting the relationship leans towards the parasitic.
Now, though, Roan Plotz of Australia’s Victoria University has discovered that red-billed oxpeckers provide another important service for black rhinos – one that might incline the pachyderms to tolerate a bit of vampirism: they warn their hosts of approaching danger.
“Every single time the birds call, the rhinos respond immediately and almost always re-orientate to face downwind,” says Plotz. “Being blind as bats and reliant on their sense of smell, they can’t detect people approaching from that direction.”
His experiments showed that the presence of oxpeckers more than doubled the distance at which rhinos detected approaching humans. Plotz says the study was inspired by a Swahili name for the oxpecker, Askari wa kifaru, which translates as “rhino’s guard.”
He suggests that reintroducing oxpeckers to areas from which they have disappeared might help rhinos avoid poachers: “I’d love to do trials using people armed with paint-guns to test that one.”
But there’s another intriguing – if speculative – possibility that emerges from Plotz’s work. Many black rhinos have permanent weeping sores at specific sites on their flanks, caused by infection with a parasitic worm. The oxpeckers feed regularly from these lesions, and the rhinos are apparently happy for them to do so.
Plotz suspects that the rhinos may be managing the worm infections in order to keep the oxpeckers close.
“The blood may be tiding the oxpeckers through periods when there aren’t enough ticks available,” he says.
He even wonders whether the lesions may represent a very early stage in the development of a brand new gland that is evolving in response to the devastating toll that poaching has had on rhino populations.
Read the paper in Current Biology.
Main image: Red-billed oxpecker on black rhinoceros in Kenya. © Martin Harvey/Getty