Ants Move Slower at Night, Get Lost More Often: Study Finds

Australian bull ants have a tough time finding their way back home in the dark, despite being nocturnal creatures, a new study has found.

The study was conducted by researchers from Australia's Vision Centre (VC) and the Australian National University's Research School of Biology, who found that ants that travel at night are more likely to be slower than the ants that travel during day. Also, these night travellers are less likely to reach their home.

Researchers used differential GPS to track the movement of the ants. The team set up a base station near the ant nest to get the exact location of ants from the nest.

Researchers followed an ant using a roaming GPS. The information that was exchanged between the base and roaming GPS gave the ant's position within a few inches.

The team found that ants that left the nest before sunset were able to reach the nest earlier than the ants that left the nest after sunset. "The 'late' ants walked more slowly, stopped more frequently and paused for longer compared to the early foragers," Dr .Ajay Narendra, one of the study authors, said. "They were also less able to travel in a straight path."

Also, ants that left the nest at midnight took longer to reach the nest. In one such example, an ant reached the nest after four hours even though reaching the nest should've ideally taken just three minutes.

Worker ants of the nest returned to the nest throughout the night, while the bull ants returned near dawn.

In one of the experiments, researchers captured foraging worker and bull ants and kept them in places that were either bright or dark.

The study team found that ants exposed to bright light started to go in the direction of the nest while the bull ants exposed to dark conditions began looking for landmarks that would lead them to the nest.

"To cope with dim or dark environments, night-active ants have larger lenses and wider photoreceptors - to capture light - compared to their day-active relatives," said Narendra in a news release.

"We found that even with this compensation, the nocturnal bull ants still take longer to get to their food sources or nests at night, " he added. "Our study shows that this is because these ants rely predominantly on surrounding landmarks to navigate, and that landmark information is less salient in the dark."

Researchers added that they aren't sure why ants keep travelling at night even though they are more likely to be slow during night.

The study is published in the journal PLOS One.