What is the evolutionary background of infrasonic sounds in elephants?

Phylogenetic Tracing:

Elephants belong to the taxonomic order Proboscidea, in which there are several extinct families and one living family: Elephantidae. Proboscidea fossils have been found as early as the late Paleocene era with a small animal called Eritherium that was about the size of a fox. Although there has been no evolutionary evidence of why infrasonic communication developed, one study shows that seismic communication is important in the nonvisual communication of subterranean mole rats of the Spalax ehrenbergi; it thus appears to be a channel of communication important in the evolution of subterranean mammals for its use in sensing danger. There are phylogenetic theories that Eritherium may have dwelled below ground (Nevo et al, 1991).

Moving from underground burrows to shallow water, researchers have also looked to analogous (perhaps homologous) skeletal structures between elephants and manatees. Features apparent in elephants reminescent of those of manatees (which most likely help in low frequency resonance detection underwater) are (O’Connell-Rodwell, Hart and Arnason, 2001):

  • Skull bones are aerated by sinuses
  • Cranium (minus mandible) consists of inflated bones that form diploe (spongy, porous, bony tissues)

Elephant skulls thus may be well adapted to low frequency detection, whether the media be acoustic or seismic.


Fig 1. Proposed phylogenetic tree of taxonomic order Proboscidea (Shoshani and Tassy, 2011)

Compared to the others:

According to the Elephant Listening Project, infrasonic calls have been recorded from captive Asian elephants (Payne, Langbauer & Thomas1986), African savannah elephants (Poole, Payne & Langbauer 1988) and African forest elephants (Elephant Listening Project in Central and West Africa). Many of them are able to detect sound in the 15-35Hz range up to as loud as 117dB, which carries sound across the desert about 10km. Along with Finbacks and Blue Whales, the elephants are the only other known animal that can detect frequencies “seismically,” meaning, at the same frequencies as some earthquakes. Figure 1 shows the range of other animals compared to elephants.


Fig 2. Frequency in Hz vs. animal demonstrating the range of elephants in contrast to other animals; ultrasound refers to frequencies above 18,000Hz and infrasound to frequencies below 20Hz.(Turga)