People like to think that animals help each other in nature, living in harmony and working for the common good. Scientists call this mutualism. Red-billed oxpeckers eat ticks from cattle and other large mammals, helping the animals while gaining a meal for themselves... or do they?
In truth this textbook example of mutualism (you scratch my back and I’ll scratch yours) may not exemplify such a happy partnership after all. After 2000 hours of observation Paul Weeks during graduate work for the University of Cambridge in England concluded that keeping the red-billed oxpeckers away from cattle didn't typically increase tick infestation. Paul Weeks also observed that excluding the oxpeckers speeded healing of skin wounds of various causes. (Red-billed oxpeckers: vampires or tickbirds? – Weeks 1999)
. His data suggests that the relationship between birds and their hosts is more complex than previously thought. Although the red-billed oxpeckers do not greatly harm their hosts, there is no evidence yet that they are actually helpful.
Weeks studied Bonsmara cattle in Zimbabwe that were either exposed to or isolated from red-billed oxpeckers. When Weeks counted the number of ticks on the cattle, both groups had the same amount – the oxpeckers were not helping to remove ticks at all.
So what were the birds up to? Weeks observed them picking at wounds so that they could feed on the cattle's blood. And, when the oxpeckers did eat ticks, they preferred ticks that had already engorged themselves – the damage to the livestock had already been done. The cattle were an oxpecker buffet, as the birds feasted on dead skin, mucus, saliva, sweat, tears, and earwax.Large view, RBO on Buffalo near Satara
Despite Paul Weeks's study, the long-standing “myth” that red-billed oxpeckers help their hosts by removing ticks prevails. Oxpeckers continue to be reintroduced into game reserves in South Africa coupled with advertising campaigns that continue to promote the “benefits” of red-billed oxpeckers for tick control. The Endangered Wildlife Trust’s Poison Working Group runs the translocation program “Operation Oxpecker”.
“Oxpeckers can be one of the farmer’s greatest natural allies on game and cattle farms. It is therefore very important to employ farming practices which offer the birds the best chance of survival by managing tick infestations with the correct products and management protocols”, they claim. Before the widespread use of toxic cattle dips, red-billed oxpeckers were found throughout the eastern part of the country as far south as Grahamstown. Now cattle farmers are encouraged to use bird-friendly dips so that these birds can return to their original range. Red-billed oxpeckers have been reintroduced successfully in Limpopo, KwaZulu-Natal, the Eastern Cape and the Kimberley area of the Northern Cape. Some farmers now have a healthy population on their property, which they believe keeps their livestock and game free of external parasites. This, in turn, anecdotal evidence suggests, stops the spread of tick-borne diseases.
According to Weeks, it may take a while for attitudes about oxpeckers to change. "The traditional view is still pretty solid."
One of the important limitations of Weeks’ studies is the fact that the cattle and oxpeckers did not coevolve and therefore the results may not be representative of the relationships between oxpeckers and their native African ungulate hosts in general. However, the oxpecker behaviour on cattle observed by Weeks was confirmed to extend to black rhinos in captivity by observations of captive oxpeckers and black rhinoceroses at Zurich Zoo, in Switzerland. (McElligott, Maggini, Hunziker and König – Interactions between red-billed oxpeckers and black rhinos in captivity 2004)
. This work demonstrated that the birds opened new wounds on their hosts. This was an unnatural situation, especially since the captive rhinos were tick-free, but it suggests that field studies of oxpeckers should focus on the frequency of feeding at wounds, and monitor the frequency with which new wounds are created on game animals.