• Alex Taylor

Poor eyesight makes black rhinos a target. But birds are helping them to survive.

Updated: May 29, 2020

Black rhinos put up with red-billed oxpeckers hitchhiking on their backs more than other species. That's because they eavesdrop on the birds’ alarm calls to help them avoid humans.

A black rhino with some hitchhiking oxpeckers, on the lookout for poachers (image by Kandukuru Nagarjun)

Black rhinos have terrible eyesight. Despite their impressive defences like large, sharp horns and tough skin, human poachers approaching from downwind can walk within about 5 metres of one. And this has resulted in their numbers falling dramatically.

Protection from poaching is vital for the survival of this critically endangered species. And it turns out, they are getting this from their hitchhiking friends, the red-billed oxpeckers.

These birds spend most of their lives on the bodies of some large herbivores in Africa. So much so that they are perfectly adapted to this life. Their tail feathers are short and stiff, propping them up like woodpeckers, their legs are short and their claws are sharp and curved for a better grip. Their bills are sharp, flat and slim to help them pry out the ticks and larvae from their hosts skin that they feed on.

Their hosts benefit, as ticks draw blood and spread disease. However, oxpeckers can also be a bit of a pain, literally, because they feed on wounds too, keeping them open and slow to heal. For this reason, they are most certainly not welcome on other mammals, such as African buffalo.

So the fact that black rhinos put up with them means that there must be something in it for them. And this was investigated by scientists.

Walking with rhinos

They walked towards the rhinos (something I’m sure they wouldn’t recommend under normal circumstances…) and recorded their behaviour, how many oxpeckers it had, and how close they could get to it.

They discovered that the rhinos without any oxpeckers spotted them only 23 percent of the time. But with them, it was 100 percent of the time, and at a much greater distance!

The more birds the rhinos carried, the further away the human was when he was seen. Yet for the poor rhinos without any, the scientists were able to get close up to them in three-quarters of their attempts.

It seems the rhinos listen to the oxpeckers’ alarm calls. When they hear them, they nearly always move to face downwind. Makes sense, this is their most vulnerable position because they can’t smell predators from that direction. It’s particularly useful when trying to detect human hunters (other predators don’t hunt from downwind, they use cover to get as close as they can.)

This adds to circumstantial evidence that the oxpecker alarm calls are specifically anti-human signals to the rhino - as well as the behavioural response to the calls there are, so far, no reports of alarm-calling in response to predators that aren’t human.

Oxpeckers saving rhinos?

Seeing humans earlier will give rhinos a much better chance of escape. At a longer distance away, the chances of a hunter’s bullet hitting a rhino is smaller, because wind can take a bullet off course, vegetation gets in the way and it takes longer for the hunter to aim, so the animal could move out of the way.

Therefore, the scientists conclude, oxpecker alarm-calling probably reduces illegal poachers’ success.

It also seems that this is a recent thing. Rhinos have been hunted by humans for around 50,000 years, but never to the extent that it has been since we started using modern weapons. We have reduced black rhino numbers from approximately 700,000 in 1850 to fewer than 2,400 in 1995.

This means that the oxpeckers’ food source (the rhinos) is under threat, and warning signals are a way to protect it and ensure their own survival. The vulnerability of black rhino to poaching has driven the evolution of eavesdropping on the birds’ calls.

I found this fascinating! It shows how species can adapt to threats, and the connections between species that should be taken into account to conserve them better.

Because there are implications for conservation. Like the rhinos, oxpecker populations have declined and become locally extinct in many areas. This is due to pesticides designed to kill the ticks accidentally killing the birds too.

The less oxpeckers there are, the more rhinos without protection there will be so, they will be more vulnerable to poaching. By re-introducing oxpeckers to rhino populations, or reintroducing both species into wildlife reserves, rhino survival could be improved, especially when park rangers fail to fully protect them against poaching.

Oh, and another lesson is that indigenous knowledge is important. Did you know, in Swahili the name for red-billed oxpeckers means ‘the rhino’s guard’?! Local people have known this all along so its time for conservation to pay more attention to it!

Regardless of who knew it first, the great news is that there may be a win-win result for both rhinos and their hitchhiking protectors!

If you know someone who would love this story of these useful birds and the blind rhinos they look after, please share it with them!

#rhino #birds #poaching #hunting #conservation

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