Acoustic Surveys
Acoustic surveys are effective for surveying forest elephants because they can cover large areas for long periods of time in dense forests that are hard to study otherwise. Acoustic surveys sample a larger area with less effort than a dung survey, the other common technique for surveying forest elephants. A single acoustic sensor can sample an area of about 3 km2 in a quiet forest, while an equivalent-effort dung transect covers only 0.1 km2. The population estimates obtained from acoustic surveys are comparable to those from dung sampling, but their precision is higher, producing confidence intervals half as wide as those from a dung count.
Since the data are recorded automatically, human bias is greatly reduced. Acoustic methods also record at night, when it is particularly difficult to gather data on forest elephants. The acoustic recorders also collect data on human activities in the area by recording noises such as chainsaws, gunshots, and vehicles. Since the stations record simultaneously, elephants are not counted twice within the same survey, which can be a problem with other methods such as aerial or ground counts.