Every month we showcase a relationship between two or more species or groups of species that can be considered a mutualism: a relationship where both members benefit. August’s Mutualism of the Month is the red-billed oxpecker (Buphagus erythrorhynchus) and their obligate hosts: large African mammals.
The birds feed almost exclusively off of what can be gleaned from the skin of these mammals. Food includes ticks, dead skin, mucus, saliva, and good old blood, sweat, and tears (Bezuindenhout and Stutterheim, 1980) (seriously!). Although blood is their preferred food, tick feeding has been the focus of much of the research done. It was thought that tick removal must be beneficial to the host mammals as ticks drain blood and are vectors for many diseases, although no one has quantified the actual benefit.
Weeks (2000), a former graduate student of the University of Cambridge, set out to see what the real deal was with these oxpeckers. He split a herd of Bonsmara oxen (Bos taurus x indicus) and allowed half of the oxen to be cleaned by oxpeckers and kept oxpeckers away from the other herd (a volunteer chased away oxpeckers during the day).
What he found was red-billed oxpecker don’t have a significant impact on ticks as was commonly thought; rather, wounds heal slower in the presence of these birds! Wounds were more numerous in the oxen exposed to the birds, an effect of the red-bills constantly tapping the cows for blood and disturbing healing wounds. Not much of a mutualism. The only benefit found was that the red-bills reduce the amount of earwax in the oxen significantly.
Moral of the story: Classic examples of mutualisms are far more complicated than originally believed!
Despite the findings of Weeks (2000) this video was posted in 2012 touting the use of oxpeckers as a biocontrol for ticks seemingly unaware of Week’s research and conclusions.
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Bezuindenhout, J.D., and S tutterheim, C.J. 1980. A critical evaluation of the role played by the red-billed oxpecker Buphagus erythrorhynchus in the biological control of ticks. Onderstepoort Journal of Veterinary Research 47: 51-75.
Weeks, P. 2000. Red-billed oxpeckers: vampires or tickbirds? Behavioral Ecology 11: 154-160.