Tiny backpacks track bats’ amazing lives in the dark

Lela Nargi

THE WASHINGTON POST – Nine years ago, Simon Ripperger was studying frugivorous – that is, fruit-eating – bats in Costa Rica.

The Ohio State University researcher tagged 16 bats with radio transmitters to keep tabs on them. But figuring out how they were moving and what other bats they interacted with, was difficult.

“I had to literally run after flying animals at night through the rainforest,” he said. “It took me five months to collect data.”

Tiny GPS devices weren’t the solution. They couldn’t transmit in real time and needed to be removed from the bats to collect data.

Instead Ripperger developed a “bat backpack” with eight engineers and scientists. This is an energy-efficient tracking system that runs on little batteries, weighs less than a penny and does not rely on GPS technology. It’s glued to a bat’s back and is so tiny it does not interfere with the bat’s ability to fly. It sends data on the bats’ movements to stations on the ground.

Scientists are using tiny backpacks on bats, such as this vampire bat, to study their movements and interactions. PHOTO: THE WASHINGTON POST

It’s also designed to fall off after two weeks, because “bats are so smart and learn how to avoid you,” Ripperger said. That means it’s hard to capture them a second time to recover a backpack. Scientists collect fallen-off backpacks from bat roosts and reuse them. And Ripperger can tag 50 bats at a time to create a wireless network of backpacks, to collect even more data.

Using the backpacks, Ripperger has discovered that vampire bats are highly social “and have lasting, humanlike friendships,” he said.

Noctule bat mothers teach their pups where the colony’s roost is by guiding them while both are in flight.

With long-tongued bats in Costa Rica, Ripperger put backpacks on bats and the flowers in which they forage for nectar. This showed him the strategies the bats use “for flying the shortest distance between flowers”.

Ripperger is trying to understand how mouse-eared bats listen for their favourite meal, ground beetles, as they “rustle as they walk over dry leaves”.

He said many scientists are interested in using the backpacks for their research. One study put them on small lizards in Germany to understand how they moved over and around train tracks. They can be used on birds, rodents and other small animals.

Ripperger hopes the backpacks will help change people’s understanding of bats.

So much knowledge about bats is hidden from humans “because (bats are) nocturnal and fast-flying,” Ripperger said. “Compared with birds, which anyone can observe with binoculars, bats are very tricky to study.”

He said that goes for even the simplest questions about bats, such as how many of any one species there are.

“The problem with lacking knowledge,” he said, is “that it makes it very easy to fear something.” Ripperger is especially upset with people who claim that the novel coronavirus pandemic is bats’ fault.

He said the virus is not transmitted directly from bats to humans. It probably goes through another animal host first. Plus, humans have destroyed many bats’ natural forest habitats. That puts us in contact with species we normally don’t meet.

Bats, he said, “eat insects to control pests. That saves farmers millions of dollars on pesticides.” Some bats pollinate flowers, and “only with their help can forests regrow. They are very important to keep ecosystems functioning.”