Rumble, Rumble. Who's There?
By Betsy Mason
/Science/NOW Daily News
31 May 2007
Elephants know the difference between good vibrations and bad, according
to new research into the big animals' low, rumbling alarm calls. They
pay attention to seismic waves made by elephants they know and ignore
those of strangers.
Behavioral ecologist Caitlin O'Connell-Rodwell of Stanford University in
Palo Alto, California, discovered in 2004 that African elephants
communicate with each other from kilometers away through ground
vibrations. Although they make the calls with their trunks, the sounds
also travel several kilometers along the surface of the ground, about as
far as airborne sounds. O'Connell-Rodwell witnessed groups of Namibian
elephants stopping in their tracks, leaning forward onto their toes, and
pressing their trunks to the ground. The animals often adopted this
listening posture before the arrival of another group of elephants.
O'Connell-Rodwell recorded various elephant calls and found that wild
elephants responded to ground vibrations alone. Researchers aren't sure
how elephants detect the waves, but they have vibration-sensitive cells
in their feet and trunks.
In the new study, O'Connell-Rodwell asked whether the elephants can tell
who is making the alarm calls. So the team recorded alarm calls made by
elephants encountering lions in Kenya and Namibia. Then they converted
the sounds into seismic waves and played them back to Namibian elephants
visiting a water hole. The elephants responded to the Namibian
vibrations by freezing, huddling, and leaving the area sooner. The
elephants appeared to detect the Kenyan calls--they sometimes paused and
looked more alert, for instance--but did not react dramatically. The
Namibian elephants also ignored control recordings of synthesized sounds
that had similar frequency and duration. The research is slated to
appear in the August /Journal of the Acoustical Society of America/.
The scientists don't know why elephants respond differently to the alarm
calls, but O'Connell-Rodwell suspects it is not due to dialect
differences. The calls from the two countries are similar in frequency
and duration. More likely, she says, is that the elephants trust the
calls from animals they know but not those of strangers.
Behavioral ecologist Jan Randall of San Francisco State University in
California, who studies kangaroo rats that use foot drumming vibrations
to communicate, agrees that the elephants may be gauging the
trustworthiness of the calls and heeding only the ones from reliable
sources. That might help them avoid expending unnecessary energy
responding to bogus calls. But alarm calls are hard to capture in the
wild, and the researchers need to test more samples, Randall says. "It's
an exciting result and it's really suggestive, but it needs some of the
follow-up work to really pin it down."
Elephant Listening Project <http://www.birds.cornell.edu/brp/elephant/>