Machine learning listened to wild elephant choruses in Kenya and found the overlapping rumbles carry clues about what the herd is doing

Elephants keep in touch with rumbles, deep calls that partly dip below what human ears can hear. About 60% of those rumbles overlap with other elephants’ calls in choruses, especially during big moments like greeting ceremonies. Most studies have left the overlapping calls out, because pulling apart several low voices at once is the same puzzle as following one conversation at a crowded party.

The clever bit

Treat the whole chorus as one message. The team used 902 recordings of adult female elephants made in Amboseli National Park between 1986 and 2022 by observers who noted in real time what each family was doing. The calls fell into six situations, including coos to calves, contact calls between separated elephants, let’s-go calls before the group moves and greeting rumbles at reunions. Machine-learning models learned the sound patterns of each situation, such as which low frequencies carry the most power, then tried to name the situation for recordings they had not trained on.

The models picked the right situation better than chance, for single rumbles and for overlapping choruses. A model trained only on single rumbles could also read choruses, which suggests each elephant in a chorus uses the same kind of call it would make alone. In cadenced, contact and greeting exchanges, the callers’ rumbles also became more acoustically similar as the exchange went on. The study was published October 1 in Scientific Reports.

It is pretty exciting that we’re able to train a model to look at an entire chorus and have some interpretation of exactly what’s going on.

— Sara Keen, senior research scientist, Earth Species Project, via scientificamerican.com

Hooray

Researchers can now study the overlapping majority of elephant conversation instead of setting it aside. The paper says future work can include chorus recordings to get bigger samples, which matters for animals where it is hard to tell who is calling, such as whales and elephants. The study also adds evidence that an elephant chorus works as a group signal.

What comes next

The team wants playback experiments, where researchers play recorded rumbles to elephants and watch how they react, to test whether rumbles growing more alike helps a family agree on a plan. Keen hopes to try similar methods on other animals that call in choruses, such as orcas and crows. The acoustic features and analysis code are public.