ATMOSPHERIC CONTROLS ON ELEPHANT COMMUNICATION

Atmospheric conditions conducive to long-range transmission of low-fre quency sound as used by elephants are found to exist in the Etosha Nat ional Park in Namibia during the late dry season, Meteorological measu rements show that strong temperature inversions form at the surface be fore sunset and decay with sunrise, often accompanied by calm wind con ditions during the early evening. These observations are used in an ac oustic model to determine the sensitivity of infrasound to the effects of (a) the strength, thickness and elevation of temperature inversion s, and (b) the growth and decay of an inversion typical of dry, elevat ed African savannas. The results suggest that the range over which ele phants communicate more than doubles at night. Optimum conditions occu r 1-2 h after sunset on clear, relatively cold, calm nights. At these times, ranges of over 10 km are likely, with the greatest amplificatio n occurring at the lowest frequency tested. This strong diurnal cycle in communication range may be reflected in longer-lasting changes in w eather and may exert a significant influence on elephant behaviour on time scales from days to many years.