Human beings are so egotistical – the self-proclaimed epitome of evolution, fashioned by a supernatural power no less, with whom the Chosen among us communicate thanks to our unique quality of language, complete with grammar and syntax, and episodic memory thanks to which we can relate our lofty experience to groveling scribes. But maybe we are not as special as we like to think. First came the revelation that other animals communicate and have opinions .
Then came the news that elephants are capable of first-order intentionality . They are aware of others and will tailor their communication accordingly. Now, Prof.
Yossi Yovel of Tel Aviv University, Dr. Lee Harten and an international team report on episodic memory and planning capacity in the wild Egyptian fruit bat. Their paper was published in the Cell journal Current Biology in July .
Similarly to first-order intentionality, episodic memory is widely considered to be a high-level cognitive ability that many assume to be unique to humans. Truth is that the Tel Aviv team and their aviating animals were preceded by a study on cuttlefish, which concluded that the mollusks were capable of episodic memory. Not only were we knocked off our pedestal, but by an invertebrate no less .
What is episodic memory? Information of recent or less recent experiences or events: what you ate for brunch and where you did so, for instance. Where you first heard that cats can speak and where the cat sat when it told you that. You might remember that one restaurant is a terrific deal while the one next door is an armpit, for example.
In the case of the fruit bat, the team demonstrated an extraordinary suite of capabilities that boil down to planning foraging routes based on spatiotemporal memories. How was episodic memory capacity in the wild Egyptian fruit bat elucidated? By tracking free-ranging wild Egyptian fruit bats living in the university's Garden for Zoological Research. How were the bats tracked exactly? Using tiny high-resolution GPS trackers attached to each bat.
"In particular, the study focused on the traits of episodic memory, mental time travel, planning ahead, and delayed gratification," the team explains, adding that episodic memory and "mental time travel" are considered unique to humans. Or had been. The team spells out that this anachronistic opinion had been debunked before them, as science established actual criteria to test "episodic-like memory" in other species.
Cuttlefish and elephants have long been known to be smart, but similar behavior has also been observed in bees (insects), scrub jays (giving a whole new meaning to the phrase "birdbrain") and in our friend the rat (in whom communication abilities and memory feats have been observed , if not appreciated, for decades). And in frugivorous monkeys too. Even today, though, observational research on intentionality in wild animals is rare: note that the elephants in the study mentioned above were only "semi-wild," while some have reported field-based evidence for future-oriented behaviors in primates – especially in regard to tool use and even manufacture.
Now, Yovel, Harten and the team have observed evidence that their free-ranging wild Egyptian fruit bats rely on mental temporal maps and exhibit future-oriented behaviors when foraging. Why? What does that even mean? It means the researchers assumed that fruit bats who live on fruit would benefit from being able to track the availability of food spatially (where are good fruit trees?) and over time (when does each tree give fruit?). In other words, they become experts on tree phenology: the timing of their fruition patterns.
Some trees sustain fruiting or nectar for weeks; some are depleted within days. Remembering which and where they are is helpful. So the team tracked bats as they flew about foraging, and documented every tree they visited over months.
In addition, sometimes the bats were prevented from foraging outside, from a day to a week. (They weren't left to starve in their colony – they were fed.) "We wanted to see whether the bats could tell that time had elapsed and behave accordingly," Harten explains.
After one day of captivity in the colony, the bats would go back to trees visited the night before, she says. But if a whole week had gone by, the older bats didn't go back to those trees but tried new ones, plausibly assuming the trees had meanwhile stopped bearing fruit. Or maybe they assumed the fruit had all been eaten.
Not so the juveniles. Teenagers everywhere only think they know everything. The older bats actually knew some critical amount of time had passed since their last visit to each tree, the researchers suggest.
They knew which trees were likely no longer worth checking. The young couldn't do that – indicating that this is an acquired skill that must be learned, the team says. Long story short, they realized the dear creatures were mapping resources in their environment in space and time.
Based on the bats' trajectories and foraging choices, they were evidently planning in advance which trees to visit, and doing so back in in the colony. The conclusion about preplanning was based on tracking which tree each bat aimed for first. "We found that usually the bats fly directly to a specific tree they know, sometimes 20 or 30 minutes away," explains co-author Chen Xing.
"Being hungry, they fly faster when that tree is further away, suggesting that they plan where they are heading. Moreover, focused on their chosen target, they will pass by other trees – even good sources visited just yesterday – indicating a capacity for delayed gratification." In addition, the team deduced that the first bats to leave the colony choose trees bearing sugar-rich fruits, while bats who leave later seek proteins, Xing adds.
"All these findings suggest that the bats plan their foraging before they leave the colony, and know exactly where they are flying and what kind of nourishment they are looking for." That demonstrates future-oriented behavior and delayed gratification on a constant basis, the team sums up. "Our study demonstrates that fruit bats are capable of quite a complex decision-making process involving the three questions indicative of cognitive abilities," Yovel says.
He defines these as "where" (each tree's location), "when" (when the tree bears fruit) and "what" (the nourishment it provides – sugar versus proteins). And that means what? That we are "not as unique as some might think," he says. "Other life-forms are also capable of forming memories and learning from them, and planning ahead, not to mention communicating what they learned," Yovel adds.
"Apparently, humans and animals are all located on a spectrum, with almost any human ability found in animals as well." Makes sense. How does all this cast on we carnivorous apes , who arose (long ago) from possibly frugivorous and/or insectivorous proto-primates ? "The fact bats eat fruit that grows in places that are permanent but change over time apparently pushed evolution of episodic memory, and it could well be that this happened in primates too," Yovel tells Haaretz by WhatsApp.
"That could be why we have such developed short-term memories.".
