Bats have built-in GPS systems: How their brains navigate the world like living compasses |

For the first time, scientists have tracked the real-time brain activity of mammals freely navigating in their natural environment. Ina study published in the journal Science, researchers from the Weizmann Institute of Science discovered that fruit bats possess an internal compass that helps them map their surroundings, functioning much like a living GPS. The bats were observed flying under open skies while their neural signals were recorded, revealing how specific brain cells were activated in response to direction. This discovery provides remarkable insight into how mammals, including humans, use their brains to orient and navigate in the real world, bridging the gap between laboratory research and natural behaviour.

The research took place on Latham Island, a small, uninhabited landmass located about 25 miles off the Tanzanian coast. Barely the size of seven football pitches, the island offered the perfect balance, a wild, natural habitat without human interference, yet contained enough to allow the scientists to track the bats’ movements.To conduct this ambitious study, the researchers transformed a rented building at Tanzania’s Central Veterinary Institute into a temporary laboratory. They equipped six local fruit bats with ultra-light brain-recording and GPS devices, the smallest ever created for field studies, to monitor their brain activity as they flew.

The expedition faced several hurdles early on. Cyclone Freddy, one of the longest-lasting tropical storms in recorded history, disrupted the team’s initial plans. With fierce winds sweeping through the region, the bats were unable to fly for nearly a week. Once the weather stabilised, the bats were released nightly to fly solo for up to 50 minutes while researchers tracked their every movement and neural response.During these flights, scientists recorded the activity of over 400 neurons located deep within each bat’s brain, neurons specifically linked to navigation and spatial orientation.

The most striking discovery was that the bats’ brains contained an internal compass system. Each time a bat turned its head toward a certain direction, such as north or east, a unique group of neurons would activate. This consistent pattern revealed that the bats were guided by a global orientation mechanism, not just local cues.According to Professor Nachum Ulanovsky of the Weizmann Institute’s Brain Sciences Department, “We found that the compass is global and uniform. No matter where the bat is on the island or what it sees, specific brain cells always point in the same direction, north remains north, and south remains south.”Previously, such activity had only been observed under controlled lab conditions. This study marked the first time it was seen in natural, outdoor environments, confirming that mammalian brains are wired to navigate the world on a larger scale than previously thought.

While some animals, like birds and sea turtles, use the Earth’s magnetic field for navigation, bats rely on something different. The researchers noticed that it took a few nights for the bats’ internal compass to stabilise, suggesting a learning process rather than an innate response to magnetism.Professor Ulanovsky explained, “If the bats had used the magnetic field, their orientation would have been accurate from the first night. Instead, we saw gradual learning; by the third night, their compass was steady.”This means bats likely depend on visual landmarks to navigate. Latham Island’s cliffs and boulders provided excellent reference points for the fruit bats, which are known for their keen eyesight. Unlike birds, these bats use sight, smell, and memory to map their surroundings, a process that requires time and experience.

You might expect nocturnal animals like bats to use the moon and stars for navigation. However, the study showed that these celestial cues played only a minor role. The bats could still orient themselves even when the moon wasn’t visible.“The moon and stars are not essential for bats to navigate,” said Ulanovsky. “However, they might help calibrate the compass during early learning, allowing bats to align what they see in the sky with what they detect on the ground.”

This discovery has profound implications beyond bats. The neurons responsible for this “internal compass”, known as head-direction cells, are also found in humans and other mammals. These cells develop early in life and help living beings maintain a sense of direction and spatial awareness.“Until recently, a person unable to navigate would not have survived,” said Ulanovsky. “Even today, orientation is crucial for daily life. Studying how these systems work in mammals helps us understand how navigation mechanisms function in the human brain, and how they may fail in conditions like Alzheimer’s disease.”At the Weizmann Institute’s home laboratory, researchers have previously built large indoor spaces, including a 200-metre-long bat tunnel, to study navigation. Yet, as this study proves, nothing compares to real-world observation.