In world first, Israeli scientists discover bats navigate like humans, using eyesight and cognitive map
‘No such study has ever been conducted on any living creature, and the findings are very interesting,’ says team from Tel Aviv University and Hebrew University
By ILANIT CHERNICK
In a world first, researchers from Tel Aviv University (TAU) and the Hebrew University (HU) of Jerusalem have discovered how bats navigate when flying long distances.
According to the study, which was released this month, bats use their excellent eyesight to build a visual cognitive map of the space around them also making use of conspicuous landmarks.
In fact, the team pointed out, this is very similar to what humans do.
According to Prof Yossi Yovel of TAU’s Sensory Perception and Cognition Laboratory at the Department of Zoology, the way animals are able to navigate over long distances has always been an ancient riddle.
“Bats are considered world champions of navigation,” he explained in a press release. “They fly dozens of kilometers in just a few hours, and then come back to the starting point.”
The team tracked fruit bats from birth to maturity, in an attempt to understand how they navigate when flying long distances.
The researchers monitored 22 fruit bat pups born in a colony raised at TAU – from infancy to maturity, tracking them as they scoured the city for food.
Their results found that the Tel Aviv bats navigate the space around them in much the same way as the city’s human inhabitants.
For this study, Yovel said the team “used tiny GPS devices – the smallest in the world, developed by our team, in an experiment never attempted before: tracking bat pups from the moment they spread their wings until they reach maturity, in order to understand how their navigation capabilities develop.
“No such study has ever been conducted on any living creature, and the findings are very interesting,” he stressed.
Professor Ran Nathan of Hebrew University of Jerusalem (HU)’s Movement Ecology Lab, who co-authored the research, explained that up until now the technologies “we had could not be used to track small wild animals in their natural habitats with enough detail required to test the existence of a cognitive map.”
His team monitored wild Egyptian fruit bats in northern Israel’s Hula Valley as part of the study.
To solve the dilemma, Nathan teamed up with TAU to develop an advanced “inverse-GPS” tracking system they called ATLAS.
After a few years of development and refinement, HU doctoral candidate and team member David Shohami, used the system to collect a large dataset of 172 foraging Egyptian fruit bats comprising more than 18 million localizations collected over 3,449 bat-nights across four years.
The scientists highlighted that the ATLAS movement data “provided the means for detailed track analysis combined with translocation experiments and mapping of all fruit trees in the study area, spanning 88,200 hectares.”
This provided researchers with detailed and accurate information from many of the bats individually over relatively long periods at relatively low cost, showing that wild bats seldom search for food randomly, but instead repeatedly forage in goal-directed, long, and straight flights that include frequent shortcuts.
The team also ruled out alternative, non–map-based strategies by analyzing simulated tracks, time-lag embedding, and other analyses of the trajectory data.
“Movement ecology has benefited from advances in tracking technology,” Nathan said. “But new ideas and novel insights have lagged behind.
“ATLAS has given us the keys to unlock previously unanswerable questions and will continue to shed light on a range of enigmatic natural phenomena,” he added.
During their research on the Tel Aviv bats, the scientists noted that for long-distance navigation the bats relied on conspicuous landmarks such as the Azrieli Towers, the Reading Power Station and Dizengoff Center.
Yovel pointed out that “bats use their sonar to navigate over short distances – near a tree, for example. The sonar doesn’t work for greater distances.
“For this, fruit-bats use their vision. Altogether we mapped about 2000 bat flight-nights in Tel Aviv,” he continued. “We found that bats construct a mental map: They learn to identify and use salient visual landmarks such as the Azrieli Towers, the Reading Power Station and other distinct features that serve as visual indicators.”
According to Yovel, the most distinct proof of this map lies in their ability to perform shortcuts.
“Like humans, bats at some stage get from one point to another via direct new routes not previously taken,” he said. “Since we knew the flight history of each bat since infancy, we could always tell when a specific bat took a certain shortcut for the first time.
The team discovered that when taking new, “unknown routes the bats flew above the buildings. Sending up drones to the altitude and location where a bat had been observed, we found that the city’s towers were clearly visible from this high angle.
“Here is another amazing example of how animals make use of manmade features,” Yovel concluddedThe findings were published as the cover story of the prestigious journal Science Magazi