"The Elephant Listening Project (ELP) of the Cornell Bioacoustics Research
Program was founded in 1999 to assess the potential of acoustic monitoring as a
tool for evaluating the abundance and health of elephants living in the dense
forest. Because forest elephants live under the dense rainforest canopy, their
numbers cannot be monitored via aerial counts as in the African savanna. Forest
elephants can only be monitored using indirect methods. The current standard for
forest elephant censusing relies on counts of dung piles. ELP is developing an
alternative method for monitoring forest elephants based on their vocalizations.
Elephants make powerful infrasonic calls (below the level of human hearing)
which travel long distances, allowing researchers to identify the presence of
elephants over large areas without visual sightings."