Bats are well known for their ability to “see” with sound, using echolocation to find food and their shelters. Some bats can also create a map made up of the sounds coming from their home range. This map can help them cover distances of 1.8 miles. The results are described in a study published on October 31 in the journal Science.

To navigate, echolocating bats use a local, directed sound beam. However, this echolocation is short range and highly directional and can better detect large objects within just a few dozen feet. Although bats have long been known to use their echolocation to avoid hitting objects and position themselves, less is known about how they navigate in flight because echolocation is limited when it comes to navigation.

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In the studyan international team of scientists conducted experiments with Kuhl’s Pipistrelle (Pipistrellus kuhlii) bats which weigh less than an ounce. Over the course of several nights, the team tracked 76 bats near their roosts. They moved them to different points within a 1.8 mile radius, but still within their home range.

The 76 bats were marked with a reverse GPS tracking system called ATLASwhich tracked bats in real time. Some bats were equipped only with the ATLAS system, while others were monitored to assess how their vision, smell, magnetic sense and echolocation influenced how they returned home to their roosts.

With echolocation alone, 95 percent of bats returned to their perches within minutes. According to the team, this demonstrates that bats can perform kilometer-scale navigation using only a highly directional and relatively local mode of sensing. However, they also found that when echolocation is not available, bats can improve their navigation using their vision.

“We were surprised to find that these bats also use vision,” Aya Goldshtein, study co-author and behavioral ecologist at the Max Planck Institute of Animal Behavior in Germany, said in a statement. “It wasn’t what we expected. It was amazing to see that, even with such small eyes, they can rely on their vision in these conditions. »

Alongside the field experiments, the team created a detailed map of the entire valley. The map was developed to visualize what each bat experienced with real-time data from the ATLAS system during its flights and understand how it used the acoustic information to find its way.

A reconstructed map of the valley in a baths echolocation study, showing how bats echolocate. CREDIT: Xing Chen

VIDEO: A reconstructed map of the valley as part of a baths echolocation study, showing how bats echolocate. CREDIT: Xing Chen

The model used data from the experiments and showed that bats tend to fly near environmental features with higher “echoic entropy.” These are areas that provide them with richer acoustic information that can supplement what they can see through their echolocation.

“During the localization phase, bats perform a meandering flight that, at some point, turns into a directional flight toward their destination, suggesting that they already know where they are,” Goldshtein said. “Bats fly closer to environmental features with more acoustic information and make navigation decisions.”

(Related: How echolocation allows bats, dolphins and even humans to navigate by sound.)

Bats can then use this acoustic information to differentiate between trees and roads and use them as acoustic cues.

According to the teamthese experiments show that Kuhl’s pipistrelles can navigate several meters using echolocation alone. When vision is available to them, they can improve their navigation by combining their two senses. They also use these acoustic cues to create a mental map for returning to their perches.