No More Wrestling Wolves to Change Batteries: The KineFox Tracker Harvests Movement Power Instead
The wily KineFox not only tracks animals' movements but uses them to power its sensors and a Sigfox transceiver — no batteries required.
Researchers from the University of Copenhagen, the Max Planck Institute of Animal Behavior, the Technical University of Denmark, ETH Zurich, and the University of Konstanz have developed a wearable for wolves and other animals which address a big problem in existing alternatives: having to wrestle the animal every time you have to change the batteries.
"When studying wildlife with GPS technology, the biggest limitation is always going to be the battery. It's enormously frustrating," corresponding author Rasmus W. Havmøller explains. "It is not uncommon that one gets to track an animal for a few months at most before the GPS device goes dead. But tracking an animal for a longer period of time is often important, as in the case with wolves here in Denmark. Therefore, we need a more reliable power source."
"Solar cells work fine for birds, but solar cells are so fragile that mammals tend to crush them," Havmøller continues. "Moreover, many mammals are nocturnal. So we needed to come up with an alternative. I had long thought about the cleverness of the automatic wristwatches that many of us wear, which harvest energy from our own body's movements."
The end result of that thinking: a battery-free wearable which uses the animal's own movement to power its electronic systems, and which works at night and in any weather. "It sure as heck works," Havmøller says of KineFox device. "The more an animal moves, the more energy it generates and the more GPS location messages it sends. Unless the equipment itself breaks, it will work throughout an animal's lifetime. At the same time, it only weighs 150 grams [around 5.3 oz] — significantly less than most other GPS trackers — so it can even be fitted onto small mammals."
The KineFox system uses a Kinetron MSG.32 kinetic energy harvester originally developed for use in the Sequent Supercharger watch, connected to a lithium-ion capacitor for storage. The stored power is then used to drive a Microchip ATtiny1627 microcontroller connected to an accelerometer, a GPS module, and a Sigfox low-power long-range wireless transceiver. When the capacitor is full, a load switch activates the rest of the hardware, captures readings, and transmits them through the Sigfox network. When the animal sleeps, the system remains powered down.
"There is no good alternative to this GPS device when it comes to serious long-term studies and studies of how animal species disperse. Because either the equipment is too big, too heavy or too fragile," Havmøller claims. "But it's really important to understand how a species moves from one place to another, and where they are shot or poisoned, for example – not least if we want to protect them better."
"There are endangered species where we know incredibly little about what they do for most of their lives," Havmøller continues. "These include tigers, which can travel thousands of kilometers, as well the Asiatic wild dogs and leopards that I’m involved with. When wild dogs reach sexual maturity, leave their mother and set out on their own, they are very vulnerable. But from that moment on, we know nothing about what they’re up to and why some die while others make it. It is a black box. I hope that this invention can remedy that."
The team's work has been published in the journal PLOS One under open-access terms.