the use of the ground or other substrate by some animals to transmit signals between individuals. Rabbits, some frogs, and kangaroo rats thump on the ground with their feet in distinctive patterns that provide cues for individual recognition and may serve to attract mates or repel intruders. Ongoing research by U.S. biologist Caitlin O’Connell-Rodwell (1965– ) has established that elephants use seismic methods for long-distance communication, including estrus calls.