Counting on technology to count elephants

From San Francisco, at a meeting of the American Geophysical Union

Researchers often serve lengthy stints in remote areas to count and monitor the movements of large animals such as elephants. In the future, however, scientists may use seismic instruments to do the job, a new study suggests.

In field tests in Namibia in 2002, Jason D. Wood, a geophysicist at Stanford University, and his colleagues buried a geophone—essentially, a sensitive microphone—near a path used by wildlife. The scientists observed passing animals and then analyzed the seismic waves generated by their footfalls.

When the researchers looked at the amount of seismic energy transmitted at various frequencies, they found that the pattern generated by elephants typically differed from that due to lions, giraffes, or people. Wood and his colleagues could distinguish passing elephants from other animals about 82 percent of the time. Team members are still working to develop a technique that enables them to accurately estimate how many elephants are in a passing group.

The geophone could pick up the footfalls of an elephant about 100 meters away, says Wood. By placing arrays of geophones near oft-used paths or watering holes, scientists could unobtrusively conduct long-term surveys of elephant populations and their movements, Wood suggests. Currently, scientists estimate elephant populations by counting dung balls or conducting aerial surveys, techniques that are time-consuming, difficult, and expensive.