Do elephants really 'never forget'?

They say "an elephant never forgets." But how much truth is there to that expression? How good is an elephant's memory?

Though it's not strictly accurate to say an elephant never forgets, the pachyderms did evolve to remember details that are key to their survival. For example, elder African elephants (Loxodonta africana) can recall the unique sounds and smells of predators (even discriminating between different groups of people, depending on their odor and clothing color), retrace their steps to find water holes in the arid savanna, and distinguish family members and associates from hundreds of other elephants.

"Being able to seek out sufficient food and water in a highly dynamic environment such as the savanna, while also managing complex social relationships and avoiding predation risk, requires a brain capable of processing and remembering detailed information," Graeme Shannon, a lecturer in zoology at Bangor University in the U.K., told Live Science in an email. "This is a critical skill that can mean the difference between life and death."

Elephants are not the only animals that forage for food in the savanna, but the unique challenges these pachyderms face demand exquisite memories. For instance, each elephant needs to eat about 330 pounds (150 kilograms) of vegetation each day, and to satisfy their voracious appetites, elephants embark on long migration routes between the wet and dry seasons. Whether they survive that migration depends heavily on their knowledge of the route.

"An elephant's memory facilitates remembering long migration routes that include tree and water resources, which are important in order to make it through a very long migration," Caitlin O'Connell, a faculty member at Harvard Medical School who studies elephant hearing, told Live Science in an email. 

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Memory becomes particularly important during a drought. A 2008 study in the journal Biology Letters observed that elephant herds with older matriarchs, who had lived through prior droughts, successfully led their herds to water — presumably by remembering how the herd had survived the prior drought.

One herd, however, was led by a young matriarch that could not have remembered how the previous generation had handled the last drought. Her herd stayed put rather than traveling through new terrain to find water, and its calves suffered a 63% mortality rate that year. The normal fatality rate during a drought is only 2%. "Hence the importance of older matriarchs as important repositories of knowledge," said O'Connell, who was not involved in the study. "And hence why long-term memory can lead directly to survival."

Elephants also need their memories to navigate what biologists call a "fission-fusion" dynamic. In this arrangement, also common among primates and some whale species, a core family unit of elephants comes into contact with hundreds of other elephants over the course of the year (fusion), only to later break off into the same core group (fission). 

"Operating in a highly complex social world takes considerable brain power," Shannon said. "It is crucial that elephants have detailed knowledge on familiar families and close associates, as well as being able to identify strangers and being more cautious when interacting with these unknown individuals," who might act aggressively and pose a threat to the family unit.

Unknown elephants are not the only threats these pachyderms need to keep in mind to survive. Shannon was a co-author of a 2011 study in the journal Proceedings of the Royal Society B: Biological Sciences that demonstrated that younger elephants underreact to recorded sounds of roaring male lions, whereas older elephants (who would remember prior lion attacks) assume defensive positions in response to the roars. 

In another study, published in the journal Proceedings of the National Academy of Sciences in 2014, Shannon and colleagues demonstrated that elephants can also identify the voices of humans who pose a threat. They found that elephants are more likely to take precautions when they hear the recorded voices of semi-nomadic Maasai people, who periodically kill elephants, than the voices of other Kenyan ethnicities. The elephants were also more likely to defend themselves when they heard the recorded voices of Maasai men, as opposed to recordings of Maasai women and children. "The incredible memories and cognitive abilities of elephants has even enabled them to use human language to determine the threat posed by different groups of humans," he said.

Elephants' unique brain structures may be what allows them to pull off these impressive feats of memory and cognition. A series of studies conducted by Bob Jacobs, a professor of psychology who specializes in neuroscience at Colorado College, has demonstrated that elephants' cortical neurons are radically different from those of other intelligent species. Jacobs thinks that the unique characteristics of these neurons suggest that elephants carefully mull over their memories. "In terms of cognition," he wrote in The Conversation, "my colleagues and I believe that the integrative cortical circuitry in the elephant supports the idea that they are essentially contemplative animals."

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Elephants also have the largest absolute brain size among land mammals, and the largest temporal lobe relative to body size; the temporal lobe is the part of the brain responsible for processing sounds and encoding memory.

The fact that elephants rely so heavily on their memory makes conservation efforts all the more necessary. When poachers target the largest elephants with the biggest tusks, they are usually placing the oldest elephants in their sights — repositories of the herd's collective memory — and those losses mean that younger elephants are left in charge of a herd that they do not have the experience to lead to safety during the dry season. 

Likewise, if elephant survival hinges on elders remembering migration routes, development that changes the landscape and cuts off crucial paths could have devastating consequences for entire herds. "Their habitat is threatened by human development blocking important migration routes, leaving them confined to marginal lands that often don't have important resources needed to survive long dry seasons," O'Connell said. "An obvious implication is the importance of preserving critical migration routes."