‘Sentinel’ Bird Found to Help Rhinos Evade Poachers

(CN) — Africa’s red-billed oxpeckers — known as “the rhino’s guard” or Askari wa kifaru in Swahili — truly live up to their indigenous names, according to research published Thursday which found the birds are instrumental in helping black rhinos avoid poachers and other humans.

The red-billed oxpecker, called “Askari wa kifaru” or the rhino’s guard in Swahili, alerts black rhinos to nearby humans and may have developed the behavior to protect food sources existing on rhinos’ bodies, a study found. (Courtesy of Jed Bird)

Oxpeckers feed on the ticks and lesions of the rhino’s body and are often found hitchhiking on the animals, which are listed as critically endangered but who have rebounded in recent years thanks to conservation efforts.

But the small black birds also behave like sentinels, sensing nearby humans and alerting their horned companions using their calls, according to the study published Thursday in the journal Current Biology.

Study co-author Roan Plotz said in a statement that poachers who track and kill black rhinos remain a major threat to the species, especially since the animals have poor eyesight.

“Although black rhinos have large, rapier-like horns and a thick hide, they are as blind as a bat,” Plotz said. “If the conditions are right, a hunter could walk within five meters of one, as long as they are downwind.”

To study oxpeckers’ effect on rhino populations, researchers tracked the number of birds in two separate herds and tagged rhinos with radio transmitters in order to avoid being detected by the birds.

Researchers found the tagged rhinos carried the birds on their backs for more than half the time they were tracked.

But untagged rhinos carried no oxpeckers in the time researchers followed them, which Plotz said could mean untagged rhinos who did carry oxpeckers simply avoided researchers altogether.

“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,” Plotz said.

To study the oxpecker’s effect further, researchers sent a team member towards a tagged rhino from crosswind while a colleague recorded the rhino’s behavior.

Factors considered by researchers included the number of oxpeckers on the rhino, the rhinos’ behavior upon approach and the distance of the team member when the rhino became defensive or when it was unsafe to get closer.

“Our experiment found that rhinos without oxpeckers detected a human approaching only 23% of the time,” Plotz said. “Due to the bird’s alarm call, those with oxpeckers detected the approaching human in 100% of our trials and at an average distance of 61 meters (200 feet) — nearly four times further than when rhinos were alone.”

The more oxpeckers on the rhinos’ backs, the greater the distance at which a human was detected by the birds, the study found.

Plotz added the distance estimates could be conservative figures since they don’t account for untagged rhinos carrying oxpeckers that the team could not follow.

An oxpecker’s alarm call always caused a rhino to reorient itself to face downwind where its senses are weakest.

“Rhinos cannot smell predators from downwind, making it their most vulnerable position,” Plotz said. “This is particularly true from humans, who primarily hunt game from that direction.”

Oxpeckers are effective in their anti-predator methods and may have even evolved their sentinel behavior over time as a way to protect their primary source of food: rhinos, the study said.

“Rhinos have been hunted by humans for tens of thousands of years, but the species was driven to the brink of extinction over the last 150 years,” Plotz said. “One hypothesis is that oxpeckers have evolved this cooperative relationship with rhinos relatively recently to protect their food source from human overkill.”

The knowledge and wisdom of indigenous people who recognized and recorded the oxpecker’s behavior should be celebrated and uplifted, Plotz said.

“We too often dismiss the importance of indigenous people and their observations,” Plotz said. “While western science has been incredibly useful, there are many insights we can learn from indigenous communities.”

Most rhinos live without oxpeckers in their environments since the bird’s populations have declined significantly over time, even becoming extinct in some areas, the scientists said.

After seeing the oxpecker’s impact on rhino populations, researchers believe reintroducing the bird to rhinos’ habitats would provide a boost to ongoing conservation projects.

“While we do not know that reintroducing the birds would significantly reduce hunting impacts, we do know oxpeckers would help rhinos evade detection, which on its own is a great benefit,” Plotz said.

The researchers did not immediately respond to a request for further comment.

Researchers said in a study Thursday black rhinos such as those living in Hluhluwe-iMfolozi Park, South Africa are alerted to human activity by calls from the hitchhiking oxpecker bird. (Courtesy of Dale R. Morris)
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