Seeing With Their Ears

The tiniest bat and mightiest toothed whale navigate and hunt in darkness using echolocation. Even some humans have this remarkable skill.

- Peter Meredith

DEEP IN THE ABANDONED mine shaft, bats were on the move. It was dusk – time for insect hunting. At the mine entrance, Kyle Armstrong knew they were coming because his bat detector device was picking up their ultrasonic echolocation calls, normally inaudible to the human ear.

It was the late 1990s. Kyle was working on his zoology doctorate at the University of Western Australia and wanted to catch some bats to collect non-lethal biopsy samples for a genetic study. The species he was focusing on was the orange leaf-nosed bat; the mine was at Bamboo Creek, in the East Pilbara, in northern WA. He’d set up a fine-mesh mist net across the entrance and was confident he’d catch a few.

The bats arrived from the depths – but refused to fly into the net. Detecting the filmy material in front of them, they spun around, tried again and spun around again. “They did this for some minutes, backwards and forwards, and then they discovered a pre-existing tear in my net, and in the blink of an eye they all zipped out through the hole and were gone,” Kyle tells me.

The experience left a lasting impression. “It brought home to me how clever bats are at processing their ultrasonic echolocation signals at high speed and finding out about their environment, even something as fine as a mist net,” he says.

For Kyle, it led to a career-long fascination with bats, their echolocation abilities and calls, particularly as a tool for identifying species. It’s all part of a branch of science known as bioacoustics. “I’m interested in bat echolocation because it underpins so much of their ecology and evolution,” he says. “You can see bats as similar to rodents, with two extra layers of complexity: they fly and they echolocate.”