Bats, which are gifted with a rare intelligence, never cease to amaze with their incredible abilities. Now a new study, published in the journal Current Biology, claims that these flying mammals have an episodic memory similar to that of human beings.
Episodic memory is the memory of autobiographical events; it’s what enables us to project ourselves in time and space. For a long time, it was thought that humans were the only ones with this ability. In recent years, however, the scientific community has discovered that some animals, including jays, also have this ability.
Researchers now claim that Egyptian fruit bats (“Rousettus aegyptiacus”), a species common to sub-Saharan Africa and the Nile Valley, have a sense of the passage of time. They came to this conclusion after analysing their behaviour in the zoological garden of Tel Aviv University, where they live freely.
Like other types of bat, Egyptian fruit bats are frugivores and are particularly fond of juicy, sweet fruit. Given their dietary preferences, scientists hypothesised that these animals remember the location of fruit trees where they can feed on their preferred delicacy.
They set out to verify this hypothesis by attaching GPS trackers to several Egyptian fruit bats, in order to follow their flight routes for several months.
It turns out that bats look both into the past and into the future when making feeding decisions, and don’t always go to the same fruit trees for food.
“We found that after one day of captivity, the bats would return to trees visited on the previous night. However, when a whole week had gone by, the older bats, based on past experience, avoided trees that had stopped bearing fruit in the interval,” said study author Lee Harten.
But young bats do not have the same reflex, suggesting that this behaviour is acquired, not innate. What’s more, the academics found that Egyptian fruit bats don’t leave their colony without a specific destination in mind: they know exactly where to go at nightfall to find food.
“Careful analysis of the bats’ movement and foraging choices indicated that they plan which tree to visit while still in the colony, thus exhibiting future-oriented behaviour and delayed gratification on a nightly basis,” the researchers wrote in their paper.
In other words, Egyptian fruit bats don’t go searching for food at random; rather, they rely on their past experiences – and, therefore, on their episodic memory – to establish a plan of action.
They seem to have a precise mental map of the position of the fruit trees they’re interested in, as well as solid botanical knowledge. In fact, they remember fruit production from one tree to the next, so they know where to head to avoid coming up empty-handed.
The findings suggest that remembering events is also present in the animal world, and isn’t necessarily a skill unique to human beings.