Rhinos have notoriously poor eyesight, so they mostly rely on their noses to understand the world around them. But there’s one interaction in which sound plays a key role. Southern white rhino males can either be dominant or subordinate. And only the dominant males hold and defend territories. New research finds that they eavesdrop on the calls of other males to know who is who.

“We found that contact calls carry information about the dominance status of the males. It means that only by listening to the calls, you can say if the male is territorial or subordinate.”

Ivana Cinková, a zoologist at the University of KwaZulu-Natal in South Africa.

She and her team spent almost two years in South Africa’s Hluhluwe-iMfolozi Park recording the social contact and courtship calls of male rhinos. Then they played those calls back to dominant territorial males and watched the responses. [Ivana Cinková and Adrian M. Shrader, Rival assessment by territorial southern white rhinoceros males via eavesdropping on the contact and courtship calls]

The researchers asked that the rhino calls not be included in this podcast due to the concern that poachers might use the calls to lure rhinos closer. Back to the reactions of the rhinos:

“They started to search for the intruder the most quickly and spent the longest time searching around for the intruder after the playback of the subordinate call, which was quite surprising.”

Territorial male rhinos hold exclusive breeding opportunities with the female rhinos. Subordinate males could thus be interested in challenging the territorial male for dominance. But dominant males rarely lose their territories to subordinate males, at least while they’re in prime condition. So responding to the challenge call quickly has little cost.

But other dominant rhinos theoretically pose a larger risk. So when territorial rhinos heard other dominant males, they oriented toward the direction of the sound. But they took their time responding. 

The researchers think that the rhinos were being careful, waiting to acquire more information before reacting. And most of them did eventually investigate the source of the sound.

Rhinos are always under a high risk of poaching, so parks and preserves usually keep tabs on every individual rhino they care for. Cinková says that understanding their social dynamics could allow wildlife managers to more effectively manage their rhino herds, which ultimately enables them to better guard and protect the animals from poachers—so that rhinos can keep on calling for a long, long time.

—Jason G. Goldman 

[The above text is a transcript of this podcast.]