Red-billed oxpeckers hitching rides on the backs of black rhinos
are a common sight in the African bush. The birds are best known
for feeding from lesions full of ticks or other parasites on a rhino’s hide.
But new research suggests that the relationship between the two species is much
more mutualistic (SN: 10/9/02).
Shouty and shrill oxpeckers can serve as an alarm bell, alerting black rhinos to the presence of
people
, scientists report April 9 in Current Biology. That could help the endangered animals evade
poachers, the researchers propose.

“Rhinos are as blind as bats,” explains Roan Plotz, a behavioral
ecologist at Victoria University in Melbourne, Australia. Even in close
proximity, a rhino might struggle to notice lurking danger by sight. But the
oxpecker easily can, unleashing a sharp call to warn of intruders.

In South Africa’s Hluhluwe–iMfolozi Park, Plotz and his
colleague Wayne Linklater of California State University, Sacramento approached
11 black rhinos (Diceros bicornis) by
foot on the open plain on 86 occasions. The team found that those rhinos with a
red-billed oxpecker (Buphagus
erythrorhynchus
) tagging along were much better at detecting the
researchers’ presence than those without. 

“Rhinos without oxpeckers on their back were able to detect our
approaches just 23 percent of the time whereas rhinos with oxpeckers detected
them every single time,” Plotz says. Rhinos listening to an oxpecker’s heads-up
also picked up on the approaching scientists from 61 meters away, more than
twice as far as when the rhinos were alone.

Red-billed oxpecker
The red-billed oxpecker serves as an alarm bell for black rhinos, signaling nearby danger. The birds often eat pests like ticks from the backs of rhinos and other mammals, including livestock. Due to the practice of applying pesticides to livestock, the oxpecker has seen its numbers decline.Jed Bird

All rhinos responded to the oxpeckers’ alarm calls by becoming
vigilant — standing up from a resting position, for example — and turning to
face downwind, their sensory blind spot. The rhinos then either ran away or
walked downwind to investigate the potential danger.

Black rhinos were once the most numerous species of rhino in the world. But poaching for traditional Chinese medicine has devastated the species (SN: 11/17/79). Though poaching has slowed since its peak in 2015, just 5,500 black rhinos remain in the wild and conservationists are searching for solutions that could permanently protect the critically endangered species.

The red-billed oxpecker has also declined. The birds feed on
ticks, including those burrowed in cattle, but for decades, farmers treated their livestock with pesticides to
kill the parasites. This inadvertently transferred the poison to oxpeckers,
causing them to die out in some regions in Africa. In turn, many black rhinos
must navigate the landscape without their avian companions. Given the study’s
findings, Plotz thinks conservationists should consider reintroducing oxpecker
sentinels to rhino populations.

“The oxpeckers are clearly adding a new depth and dimension to
rhino awareness levels,” says animal ecologist Jo Shaw, Africa rhino program
manager at World Wildlife Fund South Africa. “This emphasizes further
the complex webs between species within ecosystems and the need for
conservationists to work to ensure all functions remain intact.”

However, wildlife ecologist Michael Knight, chair of the
International Union for Conservation of Nature’s African Rhino Specialist
Group, cautions that a lot of poaching takes place during full-moon nights when
sleeping oxpeckers would be of less assistance.