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Africa's forest elephants are
targets of an acoustic monitoring effort
Back in the Cornell
laboratory, Katharine B. (Katy) Payne uses computer mapping programs to
document the movements and behavior of elephants she recorded in Africa.
By Roger Segelken
Biologists and acoustic engineers
based at Cornell will join researchers at two sites in Africa in a new
program to monitor the numbers and health of forest elephants by
eavesdropping on the sounds they make.
New monitoring procedures will be
tested in the Central African Republic, beginning in March 2000, and in
Ghana in May 2000 before expanding to other regions of the continent.
"Acoustic monitoring may give us
crucial information on the elephants about which we know almost nothing
because they live under the cover of forests," explained Katharine B.
(Katy) Payne, a research associate in the Bioacoustics Research Program of
the Cornell Laboratory of Ornithology.
"With the increasing pressure on
African elephants from the ivory trade and from illegal poachers, we
desperately need to know how many animals are still alive and what they're
doing," said Payne, whose discovery of long-distance infrasonic
communication among elephants is recounted in her book Silent Thunder
(Simon & Schuster, 1998).
Said Christopher W. Clark, Cornell's
I.P. Johnson Senior Scientist and director of the Bioacoustics Research
Program, "When you're recording animal sounds you're also monitoring their
physical environment, and this will provide insights to aspects of the
elephants' behavior and ecology that are available in no other way."
Clark's laboratory pioneered the use
of acoustic arrays for monitoring animals and developed computer-based
tools for the analysis of natural sounds.
One unnatural sound that biologists
would hate to hear -- and one that could be picked up by microphone arrays
-- is the sound of poachers who kill the animals for their valuable ivory
tusks, said Steve Gulick, a recording engineer who first captured the
calls of forest elephants in Gabon and the Central African Republic. "If
we can maintain real-time access to microphone arrays via satellite or
radio, we can keep track of some very wide areas. That monitoring of
elephant and human activity is not feasible now; we only find out about
poaching activity after the carnage, when we're walking through the fields
of carcasses."
Gulick was one of five Africa-based
researchers to meet with Cornell scientists at the Laboratory of
Ornithology in September to plan the acoustic monitoring. He said the
survey eventually could be expanded to study -- and offer protection to --
other endangered animals such as gorillas and rhinos.
"We are moving into an era when wild
populations that were considered as common commodities are being depleted,
and we're confronted with the fact that we know very little about these
populations," said John Hart, a survey planner whose long-term studies in
forest environments are supported by the Wildlife Conservation Society.
"How can decisions at any level be made about the management or trade in
endangered species without some knowledge about these populations?"
Another survey planner, Richard
Barnes, spent decades in Ghana counting elephant dung piles to chronicle
the animals' presence and abundance, and he now advocates acoustic
monitoring. "If we had some way of knowing when the elephants are moving
up and down the valley, we could then get a handle on the reasons for that
movement," Barnes said.
That is the question for researchers
at the Cornell laboratory as they prepare for the 2000 survey. Using
data-analysis programs that map a calling elephant's location from a
four-microphone array, the researchers can tell exactly where the animal
is. In past surveys researchers have been able to link an elephant's calls
to its behavior and circumstances by watching simultaneously recorded
videotapes. Other elephants' reactions to a call can be just as
informative as actions of the calling animal itself, Payne noted.
But in the densely forested
environments, researchers won't have the benefit of video surveillance.
That is why Payne and two assistants are looking for clues in hundreds of
hours of audiotapes and videotape of savanna elephants recorded in a
previous season. Payne's study is showing that the rates and patterns of
calling reflect the difference between small and large groups, and often
reveal what is going on.
"Elephants are very noisy during
mating, for instance, and the female usually makes a repetitious series of
calls when she is mounted," Payne said. "This will provide useful
information in a monitoring program because reproduction is one of the
clearest signs of a population's health." Some of the elephants' most
information-rich calls are produced in the infrasonic range, which is too
low for human hearing until the tape is speeded up. Infrasonic calls are
audible to other elephants miles away, allowing separated animals to find
one another.
The sound data is eagerly awaited by
Andrea Turkalo, who spent the last nine years documenting the demography
and behavior of some 2,000 forest elephants in the Central African
Republic. Most of her observations took place in a mineral-rich clearing
called Dzanga-sanga. What the elephants do when they return to the forest
-- and how many elephants are still to be counted -- remains a mystery
that partly could be solved by the high-tech eavesdropping, Turkalo
anticipates.
The first phase of the forest
elephant acoustic monitoring is supported by a Species Action grant from
World Wildlife Fund and is conducted at the Bioacoustics Research Program,
a unit of the Cornell Laboratory of Ornithology. During last month's
gathering, which was sponsored by the Cornell laboratory, World Wildlife
Fund, Wildlife Conservation Society and Conservation International, the
prospective collaborators wrote proposals to fund the remaining phases.
Explaining why a bird lab is aiding
elephants, Cornell Laboratory of Ornithology Director John W. Fitzpatrick
said: "Our mission explicitly acknowledges that we are here for the
protection and interpretation of the Earth's biological diversity. All
organisms, large and small, are linked. Elephants just happen to be one of
the bigger links."
October 21, 1999
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