Relationships between the animals in the Kruger are often regarded as symbiotic – mutualism, parasitism or predatory – but have we really spent time watching the outcomes of these interactions. The ant-lion and the ant, the spider-hunting wasp! Egrets and buffalo, crocodiles and plovers…
Last week I watched the vampires of the Kruger at work – Red-billed oxpeckers versus impalas was on the cards, and my immediate thoughts of this perceived mutually beneficial relationship were at stake.
The diet of a red-billed oxpecker is a protein rich platter of tit bits and ticks from the skin of large African mammals. This platter includes dead skin, ixodid ticks, mucus, saliva, blood, sweat and tears. They spend their days (not nights) busily feeding off the bits and pieces, the gorged female ticks and the dry skin of the mammal. Great news for mammals with expensive parasites inflicting bites, draining the blood and often leaving disease in their wake. So yes, my first thoughts were all ear-marked to be filed under ‘mutualism’.
Are they really tick doctors? Evidence in several behavioural studies presents a different set of arguments. Impalas are far better at removing their own ticks than red-billed oxpeckers are. Red-billed oxpeckers are often not even looking for ticks, but rather worrying the wounds left by ticks, and if you really think about it – their preferred diet are fully gorged ticks that have already bitten, taken all the blood they can, and left infection in their wake. So what is actually beneficial about the removal of the tick after the fact?
Some people will stick to their guns and say but it is beneficial because often oxpeckers will reach the places that impalas cannot reach like the head, neck and ears for instance – look at the picture in the above slider!
My point is that there is so much talk about impalas and other mammals benefiting from the tick removal services of the red-billed oxpeckers we tend to overlook the wound-feeding behaviour of these vampires. I’m sure science cannot tell you if they make wounds but I can tell you that they worry wounds persistently. Often the oxpeckers I’ve watched and recorded will completely ignore the ticks and head straight towards an open wound for pint or two!
This photo shows the blood, sweat and ears it takes to fully understand the differences between parasitism and mutualism. Sometimes our world is not as different. Makes you think – doesn’t it?