Differential weighting of lion vocalizations and oxpecker alarm calls in giraffes.

Prey often assess predation risk using multiple sources of information that differ in immediacy and reliability. How prey differentially weight direct predator-associated cues and heterospecific alarm cues remains a central question in behavioral ecology. To investigate this, playback experiments were conducted on free-ranging, predator-experienced Southern giraffes (Giraffa giraffa), using lion (Panthera leo) vocalizations and red-billed oxpecker (Buphagus erythrorhynchus) alarm calls presented in different positions within sequential playback trials. Lion vocalizations consistently elicited strong vigilance responses regardless of playback presentation order, indicating that giraffes assigned greater behavioral weight to direct predator-associated information. Giraffes also responded to oxpecker alarm calls, although responses were generally weaker and more variable than responses to lion vocalizations, suggesting that indirect heterospecific cues were weighted less strongly than direct predator cues. Evidence that preceding playback exposure strongly influenced subsequent vigilance responses was limited, as lion vocalizations continued to elicit stronger responses than oxpecker alarm calls across successive playbacks. Females additionally exhibited generally stronger vigilance responses than males across playback conditions. Together, these findings suggest that giraffes differentially weight multiple sources of risk-related acoustic information during antipredator responses.