It turns out that humans might not be the only species that have individualized identifiers for each other. A new study found that African savanna elephants, an endangered species, have name-like calls for each other that resemble human names — a finding that potentially "radically expands the express power of language evolution."

Researchers analyzed the rumble — "a harmonically rich, low-frequency sound that is individually distinct" — of African savanna elephants, which are listed as endangered on the IUCN Red List as populations continue to decline, largely due to poaching and land development. Specifically, researchers looked at 469 rumbles of three different types — contact, greeting and caregiving — from female-offspring groups between 1986 and 2022. Using a machine-learning model, they identified the recipients of more than 27% of those calls.

These elephants are known for traveling with family units of about 10 females and their calves, and several family units will often combine to form a "clan," according to the World Wildlife Fund, with males only coming around during mating.

The researchers also looked at the reactions of 17 wild elephants to call recordings that were addressed to them or another elephant. The elephants who heard recordings addressed to them had quicker and more vocal responses than those who heard recordings addressed to other elephants, researchers found.

And what they found is that the elephants — the world's largest terrestrial species, according to the World Wildlife Fund — do indeed have individual vocal identifiers, "a phenomenon previously known to occur only in human language." Other animals known to use vocal labels, like parakeets and dolphins, solely do so through imitation, researchers said in the study, which was published Monday in the journal Nature Ecology and Evolution.

Videos shared by researchers show how the elephants respond to call recordings addressed to them. In one, an elephant named Margaret appears to almost immediately perk up to a rumble recording addressed to her. In the video caption, researchers said she "immediately raises her head and then calls in response after a few seconds." A separate video shows Margaret raising her head to a call addressed to another elephant, but not responding.

Another elephant named Donatella shows the animal issuing a call response after hearing her name and approaching the recording.

More research on these observations is needed, the study authors said, particularly to better understand the context surrounding the calls. But so far, these results have "significant implications for elephant cognition, as inventing or learning sounds to address one another suggests the capacity for some degree of symbolic thought," they said.

African savanna elephants are found across nearly two dozen countries, including Botswana, Zimbabwe, Tanzania, Kenya, Namibia, Zambia and South Africa. In 2021, this species, as well as its close relative, the African forest elephant, received degraded conservation status.

According to the IUCN, the forest elephant species was demoted to critically endangered, while the savanna elephant was listed as endangered, whereas before, both species were "treated as a single species" that was classified as vulnerable. The new status came after findings that forest elephant populations had declined by more than 86% over the course of 31 years, while savanna elephants declined by at least 60% in a half-century.

"With persistent demand for ivory and escalating human pressures on Africa's wild lands, concern for Africa's elephants is high, and the need to creatively conserve and wisely manage these animals and their habitats is more acute than ever," assessor and African elephant specialist Kathleen Gobush said at the time.