Roaming the open bush and scrublands of sub-Saharan Africa, African savannah elephants communicate with each other through low-frequency rumbles, often occurring in overlapping choruses. This cacophony of sounds can be tricky to analyse \u2013\u00a0but a new study now reveals its intricacies and purpose.<\/p>\n
The research was led by scientists from\u00a0ElephantVoices\u00a0and\u00a0Earth Species Project, with collaborators from Amboseli Trust for Elephants. The findings are\u00a0published\u00a0in the journal\u00a0Scientific Reports<\/em>.<\/p>\n Overlapping, multi-caller vocalisations \u2013 often called choruses \u2013 are very common in the animal kingdom. They\u2019re used by chimpanzees, sperm whales, male Atlantic spotted dolphins, green woodhoopoes and acorn woodpeckers, among many others.<\/p>\n These vocalisations can carry rich social information, so they\u2019re very important to scientists \u2013 but they\u2019re also difficult to study. Separating out the many overlapping voices in a chorus comes with a phenomenon known as the ‘cocktail party problem’, wherein the brain focuses on one particular stimulus, excluding the others.<\/p>\n Elephants communicate with very low-pitched rumbles (many of them below the range of human hearing). These rumbles encode several distinct types of information – individual elephants have unique vocal signatures, and vary with age, sex, and emotional and psychological state of the animal. Previous studies have shown that these rumbles can also sound different depending on the population or even social groups within that population.<\/p>\n The structure of some rumbles has also been shown to vary depending on the individual being addressed, serving as a form of ‘name’.<\/p>\n Even with all of this information being known about single elephant rumbles, rumble choruses are less studied and understood \u2013 and 60 per cent of rumbles happen in choruses, with two or more elephants rumbling at the same time.<\/p>\n To close that gap, researchers turned to machine learning to help them analyse recordings of wild families of African savannah elephants (Loxodonta africana<\/em>), captured over four decades of fieldwork in Amboseli National Park in Kenya.<\/p>\n \u201cOur study of elephant choruses was based on the voices of individually known Amboseli elephants calling in known contexts. Over half of elephant calls overlap with other callers, sometimes producing a cacophony of sound that is difficult to tease apart and measure,\u201d said Dr. Joyce Poole, scientific director at ElephantVoices.<\/p>\n The choruses were recorded during six different social and behavioural contexts, including greetings, maintaining contact when separated, comforting and reassuring calves, and exchanges associated with coordinating movement.<\/p>\n