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Does Lucius Fox know? Tiny tech tracks bats (and more)

  • A newly developed tracking device that fits like a tiny backpack allows scientists to monitor small animals.
  • The wireless biologging network (WBN) device allows for proximity sensing, high-resolution tracking, and long-range remote data download all at the same time.
  • The capability of the WBN device to track associations is providing scientists with new insights into animal behavior and conservation solutions.
  • The device, weighing just 2 grams (0.07 ounces), is designed to be glued onto the back of animals like bats and eventually fall off after a few weeks.

Small, social, fast-moving animals like bats are notoriously difficult to study. Where do they go? Who do they spend time with? Now, scientists have a new tool to answer questions like these: an ultra-light tracking device that fits like a tiny backpack.

The newly developed wireless biologging network (WBN) device, described in PLOS Biology, is designed to be glued onto small animals to monitor their movements and interactions in real-time. It makes use of ground-based tracking and Bluetooth-style connectivity, similar to a smartphone.

The WBN sensor node on a fingertip. Photo by Simon Ripperger.

From conception to completion, the device took a team of computer scientists, biologists and engineers seven years to create. The key innovation was designing it to be automated, energy-efficient and powerful enough to transmit a signal from the inside of structures like caves and tree trunks. The WBN also enables proximity sensing, high-resolution tracking, and long-range remote data download all at the same time.

Weighing less than 2 grams (0.07 ounces), the devices are lightweight enough for an animal as small as a vampire bat, which weighs between 28 and 42 grams ( 1 and 1.5 ounces), to wear. The backpack, though glued on, is attached delicately so it will scrape off in the roost after a few weeks.

“Using backpacks on bats saves weight and it also makes sure the sensors fall off easily,” said Simon Ripperger, lead author of the paper and a postdoctoral scholar at Ohio State University who helped develop the device, said in a statement. “We don’t really want the bats to have that burden of additional weight for extended time periods.”

The size of the WBN sensor node compared to a serotine bat (Eptesicus serotinus). Photo by Carola Radke.

These high-tech backpacks were used to demonstrate that common vampire bats (Desmodus rotundus) in captivity developed the same social bonds they maintained in the wild. These results were published in a popular study released on Halloween in 2019.

One key advantage of the WBN system is its energy efficiency. The device uses only one-fortieth of the energy of an AAA battery. The receivers are in a low-energy mode and only “wake up” when tagged animals are close to each other.

“[W]hen they receive a signal from another bat, and then they are shouting, ‘I’m here, I’m here!’ and there’s another receiver that comes into full consciousness and exchanges data,” Ripperger said. “That’s one way we conserve power consumption.”

A vampire bat (Desmodus rotundus) wearing a WBN device. Photo by Sherri & Brock Fenton.

The capability of the WBN devices to track associations is providing scientists with new insights into animal behavior. For instance, Ripperger’s team deployed the devices among mother bats and their offspring. They found that while the mothers guide their offspring to new roosts, the offspring also seemed to be able to learn where and how to forage on their own.

“Those are important insights when we think about hand raising baby bats that people find and releasing them later on,” Ripperger told Mongabay. “If they would rely on social contact to learn to forage, then the chances for survival of hand-raised bats might be pretty low. Luckily this does not seem to be the case.”

The team is currently starting a project to track sand lizards along train tracks. Understanding when and where lizards are on the tracks could have a direct application for conservation such as making sure rail maintenance occurs when the lizards are not as likely to be present.

“In general,” Ripperger said, “getting deeper insights into animal behavior will help us to develop better conservation measures for specific species.”

Male sand lizard (Lacerta agilis) Photo by Christoph Caina (CC BY 3.0)

Banner image of a Tagged noctule bat (Nyctalus noctula) by Simon Ripperger

Citations:

Ripperger, S. P., Carter, G. G., Page, R. A., Duda, N., Koelpin, A., Weigel, R., … Robert, J. (2020). Thinking small: Next-generation sensor networks close the size gap in vertebrate biologging. PLOS Biology18(4), e3000655. doi:10.1371/journal.pbio.3000655

Ripperger, S. P., Carter, G. G., Duda, N., Koelpin, A., Cassens, B., Kapitza, R., … & Mayer, F. (2019). Vampire bats that cooperate in the lab maintain their social networks in the wild. Current Biology29(23), 4139-4144. doi:10.1016/j.cub.2019.10.024

Liz Kimbrough is a staff writer for Mongabay. Find her on Twitter @lizkimbrough

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