Not so far: attenuation of low-frequency vocalizations in a rainforest environment suggests limited acoustic mediation of social interaction in African forest elephants

• Published in: Behavioral ecology and sociobiology Vol. 72; no. 3; pp. 1 - 11
• Main Authors: Hedwig, Daniela, DeBellis, Maya, Wrege, Peter Howard
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer 01.03.2018; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Acoustic attenuation; Animal behavior; Animal communication; Animal Ecology; Behavioral Sciences; Biomedical and Life Sciences; Clearings (openings); Elephants; Forests; Life Sciences; Original Article; Playback; Rainforests; Social organization; Sound; Sound waves; Vocalization behavior; Wave reflection; Zoology; Acoustic adaptation; Fission-fusion; Vocal communication; Detection distance; Ambient noise
• ISSN: 0340-5443; 1432-0762
• DOI: 10.1007/s00265-018-2451-4

Forest elephants Loxodonta cyclotis aggregate in large numbers in forest clearings. Whether they maintain contact as they move through the forest and are able to coordinate these aggregations, similar to the fission-fusion sociality of the well-studied savanna elephants Loxodonta africana, is currently unknown. Since sound attenuates faster in closed as compared to open habitats, the lowfrequency rumble vocalizations of forest elephants may exhibit smaller detection ranges than measured for those of savanna elephants, which may restrict the ability of forest elephants to coordinate interactions between separated family units. Here, we modeled the attenuation of forest elephant rumbles using amplitude measurements of rumbles recorded in a rainforest in Gabon and estimated the distances at which elephants might be able to detect them under observed ambient sound conditions. Our results suggest an attenuation rate less than predictions of spherical spreading loss, suggesting that reflection of the sound waves within the forest results in constructive interference. Nevertheless, we found that forest elephant rumbles of average dominant frequency (31.07 Hz) under average ambient sound levels would not be detectable farther than 0.8 km. Moreover, for 50% of analyzed rumbles, the harmonic structure was completely attenuated at only 100 m. However, we estimated detection distances of up to 3.2 km for rumbles of average dominant frequency when ambient sound was at its lowest. Our findings suggest that long-distance communication to coordinate interactions among separated family units may be limited in forest elephants, with potentially important consequences for their social organization.