Game hunters who've taken elephants as trophies in Tanzania and Zimbabwe are banned from importing any of the animals into the US, according to new ruling by the US Fish and Wildlife Service. (Photo : Pixabay)

Elephants make rumbling sounds while departing from water holes in order to communicate within the group, finds a new study.

Elephants are social animals which live in herds, where the females dominate hierarchical structure.

An elephant group consists of only females and calves. Male elephants between age groups of 12 and 15 leave the herd and form their own group. While the female with a dominant rank becomes the head of a group, the other members of the group also have roles in their social structure.

Elephants are known to make rumbling sounds to communicate with others so as to keep track of the herd's movements or when a male wants to mate with a female.

Now a new study suggests that elephants also give soft rumbles when they have to signal the other members of their group, shedding light on their cooperative work and how organized they are.

Caitlin O'Connell-Rodwell, from the Stanford University School of Medicine, has been studying African elephants in the wild for 20 years and during her first observation in 1994 and then in 1995, found that elephants make soft rumbles while departing a water hole. At that time, her research team had set up scientific observation sites at five watering holes in the Etosha National Park, Namibia.

When elephants decide to depart a water hole, the head of the herd moves away from the group and gives soft rumbling calls by flapping her ears. This, in turn, provokes other members of the group who are at the top of the hierarchical structure to make similar sounds before they finally depart from the water hole, explained O'Connell-Rodwell.

Apart from making rumbling sounds, elephants also make repeated calls that could be heard by other groups at a longer distance by making sounds through air and ground vibrations. They do so to inform other groups not to come near the water hole until they depart from there.

Such behavior gives insight into how these elephants work together as a group. "These vocalizations facilitate the bonds between the elephants to be able to work together," O'Connell-Rodwell said in a statement.

"It's the measure of an organized society. It demonstrates how another social animal grouping organizes itself through vocalizations," she said.

O'Connell-Rodwell also described how the elephants work together to save calves from drowning. When a calf fell in a trough, O'Connell-Rodwell noticed that the high-ranked females tried to save the young one, while the calf's siblings were giving comfort to the calf.

The researcher is further planning to study if the vibratory sounds of elephants could help in research on hearing aids, as vibratory signals are easily detectable.

The findings of the study are published in the October issue of Bioacoustics.