Red-bellied Oxpeckers are Indeed Black Rhinos' Body-guards Against Humans

A study on Black Rhinos (Diceros bicornis) revealed what the Swahili knows all along: red-bellied oxpeckers (Buphagus erythrorhynchus), traditionally known in Swahili as  Askari wa kifaru, or 'the rhino's guard" are indeed the rhino's sentinel. 

The oxpecker is known to clean bugs and larvae from lesions of the rhino. However, the bird also does something more: it hisses loudly when spotting danger, providing a sort of secondary warning system to the rhino.

In a paper published in Current Biology, researchers tracked the wild black rhinos. They found that those that are carrying the red-bellied oxpeckers are better at avoiding and sensing humans than those with no oxpecker companion.

Conservation efforts have helped improve the critically endangered black rhino's numbers. Poaching, however, of these species remains a threat. 

Black rhinos may have significant, rapier-like horns and a thick hide, but they are blind as bats, explained Roan Plotz, a behavioral ecologist at Victoria University, Australia., and co-author of the study. Oxpeckers, the birds that feed on the ticks and lesions on the rhino's body, may make up for the rhino's eyesight by alarming the rhino should they sense humans nearby.

The study team recorded the number of oxpeckers on two groups of the rhinos they encountered. Rhinos were tagged with radio transmitters, allowing researchers to track them while evading detection from oxpeckers carried the bird more than half the time. The untagged rhinos were without woodpeckers most of the time. "Using the differences we observed between oxpeckers on the tagged versus untagged rhinos, we estimated that between 40% and 50% of all possible black rhino encounters were thwarted by the presence of oxpeckers," says Plotz.

The study team did a "human approach" experiment, where one researcher would walk towards the rhino from crosswind while the rhino's behavior is recorded. The study team recorded the number of oxpecker on the rhino, the rhino's behavior upon approach, and the distance of the researcher when the rhinos became vigilant or are on the defensive mode of an approaching human. 

The experiment showed that rhinos without oxpeckers detected humans by 23% of the time. In contrast, rhinos with oxpeckers detected approaching humans in 100% of the trials at an average distance of 60 meters. The researchers also noted that the more the oxpeckers the rhino carried, the farther the distance the human was detected. 

When an oxpecker gives an alarm call, it will re-orient itself to face downwind, their sensory blind spot. "Rhinos cannot smell predators from downwind, making it their most vulnerable position.", Plotz said.

In summary, the study results conclude that oxpeckers are strategic companions that protect rhinos from an encounter with people and develop anti-predator strategies. Some scientists suggest that oxpeckers developed this adaptive behavior to protect their source of food, which is the rhino's ticks and lesions. Humans have hunted rhinos for tens of thousands of years. This act led to the species brink of extinction in the last 150 years. Scientists believe that oxpeckers evolved this mutually beneficial relationship to protect their food source. 

Oxpecker's population has also significantly declined over the years. In some local areas, the bird is becoming extinct. Because of this, most wild black rhinos' populations do not have oxpecker companions in their environment. 

This study suggests that the reintroduction of the oxpeckers would significantly reduce hunting impacts as oxpeckers are now known to aid rhinos in evading detection. 

These findings also highlight the importance of local knowledge. "We too often dismiss the importance of indigenous people and their observations. While western science has been incredibly useful, there are many insights we can learn from indigenous communities.", according to Plotz.