Oxpeckers Help Rhinos Evade Humans

Area of Science:

• Behavioral Ecology
• Interspecies Communication
• Conservation Biology

Background:

• Evolutionary theory posits that solitary species benefit most from eavesdropping on heterospecific alarm calls.
• Empirical evidence for solitary species eavesdropping on alarm calls is limited.
• Red-billed oxpeckers (Buphagus erythrorynchus), known as "rhinos' guards," associate with black rhinos (Diceros bicornis).

Purpose of the Study:

• To investigate the role of red-billed oxpeckers as sentinels for black rhinos.
• To quantify the impact of oxpecker alarm calls on rhino detection of human approach.

Main Methods:

• Conducted 86 experimental approaches to 11 black rhinos over 27 months in Hluhluwe-iMfolozi Park, South Africa.
• Varied the number of resident oxpeckers present during approaches.
• Utilized radio telemetry to locate rhinos.

Main Results:

• Oxpeckers facilitated rhino evasion of detection in 40-50% of encounters.
• Oxpecker alarm calls increased rhino detection rates from 23% to 100% and detection distance from 27m to 61m.
• Each additional oxpecker increased rhino detection distance by 9m; alerted rhinos faced downwind, indicating threat proximity.

Conclusions:

• Oxpeckers effectively serve as anti-human sentinels for black rhinos, confirming the importance of depredation in the evolution of eavesdropping.
• Rhino-oxpecker interactions demonstrate a crucial interspecies relationship for conservation.
• Reintroduction of oxpeckers to rhino populations is recommended to reinstate their sentinel role.