Study Finds Rhinos ‘Talk’ With Sounds Too Low for Human Ear

Rhinoceroses emit the same kind of low-frequency sounds that elephants use to communicate with one another, scientists at an international conference at San Diego’s Hanalei Hotel reported Thursday.

“This is the first report of rhinos doing this,” said Joseph C. Daniel Jr., a collaborator in the study. “The initial observation is great fun, and of course that’s what we’re coming to the conference with, but our excitement is partly related to how we can apply this ultimately as well.

“Ultimately we hope to be able to demonstrate reliably that there are certain sound patterns that relate, for instance, to reproduction in various ways,” said Daniel, the dean of sciences at Old Dominion University in Norfolk, Va.

There are only about 8,500 rhinos left in the world, spread among five species in Asia and Africa. Scientists say they need to know more about rhino habits to assure their survival in the wild, as well as to help captive breeding programs. About 300 rhino conservationists from around the world are attending the conference this week and working on plans to increase the chances for the species’ survival.

In the study reported Thursday, Old Dominion student Elizabeth von Muggenthaler used a special low-frequency tape recorder to record rhinos at four different zoos. The signals were analyzed with equipment borrowed from NASA.

What von Muggenthaler found was distinctive patterns for different individual rhinos, different sexes and different species. Like such sounds in elephants, all occurred at frequencies below 20 hertz. The threshold for human hearing is about 60 hertz.

“Everybody seems to have kind of suspected this, but nobody’s quite gotten around to doing it, or perhaps had the equipment to do it. And consequently they’re delighted that someone now is demonstrating it,” Daniel said.

Indeed, one person was so excited about the technique that he was hoping to use it to “call” Sumatran and Javan rhinos in the tropical forest, von Muggenthaler said.

“I had to tell them that he was going to have a real problem dragging a 6-foot by 4-foot speaker into the rain forest along with a generator for his amplifier. He was really frustrated,” von Muggenthaler said.

But she suggested an alternative: “I told him what he could do is take an oscilloscope, which shows you what specific sound patterns it is hearing, and a very good directional microphone, and you could go to the rhinos,” by tracking their low-frequency sounds in the forest.

Sharon Joseph, lead mammal keeper at the San Diego Wild Animal Park, said the Old Dominion research fits with what she observes in rhinos at the park.

“It makes total sense,” Joseph said. “Especially in the white rhinos, which live in herds and don’t need to communicate over long distances, their vocal communication is probably a lot more subtle than that of more solitary rhinos.”