Elephants are the terrestrial animal in which the production of infrasonic calls was first noted by M. Krishnan <ref name="Krishnan 1972">{{cite journal|last=Krishnan|first=M|title=An Ecological Survey of the Larger Mammals of Peninsular India|year=1972|journal=The journal of the Bombay Natural History Society|volume=69|pages=26-54}}</ref> was, later discovered by Katy Payne.<ref>{{cite book|last=Payne|first=Katy|title=Silent Thunder: In the presence of Elephants|year=1998|publisher=Simon & Schuster|___location=New York}}</ref> The use of low frequency sounds to communicate over long distances may explain certain elephant behaviors that have previously puzzled observers. Elephant groups that are separated by several kilometers have been observed to travel in parallel or to change the direction simultaneously and move directly towards each other in order to meet.<ref name="Langbauer et al 1991">{{cite journal|last=Langbauer|first=W. R.|author2=K. B. Payne |author3=R. A. Charif |author4=L. Rapaport |author5=F. Osborn |title=African elephants respond to distant playbacks of low-frequency conspecific calls|journal=J. Exp. Biol.|year=1991|volume=157|pages=35–46}}</ref> The time of [[estrus]] for females is asynchronous, lasts only for a few days, and occurs only every several years. Nevertheless, males, which usually wander apart from female groups, rapidly gather from many directions to compete for a receptive female.<ref name="Langbauer et al 1991" /> Since infrasound can travel for very long distances, it has been suggested that calls in the infrasonic range might be important for long distance communication for such coordinated behaviors among separated elephants.<ref name="Langbauer et al 1991" /><ref name="Payne et al 1986">{{cite journal|last=Payne|first=K. B.|author2=W. R. Langbauer |author3=E. M. Thomas |title=Infrasonic calls of the Asian elephant (Elephas maximus|journal=Behav. Ecol. Sociobiol.|year=1986|volume=18|pages=297–301|doi=10.1007/bf00300007}}</ref>
