Wild bats with enhanced cognitive abilities previously thought to be exclusive to humans

Researchers at Tel Aviv University followed free-ranging Egyptian fruit bats in a colony based at Tel Aviv University’s I. Meier Segals Zoological Garden to answer a long-standing scientific question: Do animals have high-level, complex cognitive abilities previously thought to exist only in humans? The study focused on features of episodic memory, mental time travel, forward planning, and delayed gratification, leading to some very exciting findings.

The article is published in Current biology.

The study was led by Prof. Yossi Yovel and Dr. Lee Harten of the School of Zoology and the Sagol School of Neuroscience at Tel Aviv University. Other researchers included Xing Chen, Adi Rachum, Michal Handel and Aya Goldstein of the School of Zoology; Lior de Marcas of the Sagol School of Neuroscience; and Maya Fenigstein Levi and Shira Rosencwaig of the National Public Health Laboratory of the Israel Ministry of Health.

Professor Yovel explains: “For many years, cognitive abilities to remember personal experiences (episodic memory) and to plan were thought to be exclusive to humans. But a growing body of research suggests that various animals also possess such abilities, but almost all of these studies have been conducted in the laboratory, as field studies on these issues are difficult to perform. To try to test these abilities in wild animals, we designed a unique experiment using the free-ranging fruit bat colony based in the I. Meier Segals Zoological Research Garden at TAU.”

The researchers hypothesized that bats that rely on fruit trees for survival would evolve an ability to track food availability both spatially (where are the fruit trees?) and temporally (when does each tree produce fruit?). As they roam landscapes with many fruit and nectar trees, they would mentally track resources in order to revisit them at an opportune time.

To test this hypothesis, a tiny, high-resolution GPS tracker was attached to each bat, allowing them to document flight routes and trees visited over several months. The vast data thus collected was analyzed in depth, producing astonishing results.

The first research question was: Do bats create a temporal map in their minds? To investigate this question, the researchers prevented bats from leaving the colony for varying periods of time, ranging from one day to one week.

Dr Harten explains: “We wanted to see if bats could recognise that time had passed and behave accordingly. We found that after a day in captivity, bats returned to trees visited the previous night. However, after a full week, older bats, based on their past experience, avoided trees that had stopped bearing fruit in the meantime.”

“In other words, they were able to estimate how much time had passed since their last visit to each tree, and knew which trees bore fruit for a short period of time and were no longer worth visiting. Young, inexperienced bats were unable to do this, indicating that this is an acquired skill that must be learned.”

While the first research question was about past experiences, the second was about the future: Do bats have future-oriented behaviors? Are they able to plan ahead? To answer this question, the researchers observed each bat’s path to the first tree of the evening, which could indicate plans made before leaving the colony.

Researcher Chen Xing said: “We found that bats typically fly directly to a specific tree they know, sometimes 20 to 30 minutes away. Because they are hungry, they fly faster when that tree is farther away, suggesting that they are planning their destination. In addition, focused on their chosen target, they will pass by other trees, even good sources visited the day before, indicating a capacity for delayed gratification. We also found that the first bats to leave the colony choose trees with sugar-rich fruits, while bats that leave later seek out proteins.”

All these findings suggest that bats plan their foraging before leaving the colony and know exactly where they are flying and what type of food they are looking for.

Professor Yovel added: “The cognitive gap between humans and animals is one of the most fascinating problems in science. Our study demonstrates that fruit bats are capable of a fairly complex decision-making process involving the three questions indicative of cognitive abilities: Where? (the location of each tree); When? (when the tree bears fruit); and What? (the food it provides – sugar or protein).

“Once again, we see that the divide is not clear-cut and that humans are not as unique as some might think. Apparently, humans and animals are all on a spectrum, and almost all human abilities are also found in animals.”