Nature Lab

Tracking Wildlife Via Satellite

With GPS collars, biologists collect more data in less time

Tracking the movements of wildlife provides vital information for conservation work. In the 20th century, tracking animals by car or on foot with VHF radio transmitters became the norm. More recently, the addition of GPS to traditional radio collars has begun to change that. 

Radio tracking means going into the field regularly, using an antenna and receiver to pick up the radio frequencies of transmitters attached to study animals, and “then what you do,” explains MDC Elk Biologist Aaron Hildreth, “is get a [compass] bearing on where the signal’s coming from, then drive or walk somewhere else in fairly quick fashion, pick up that signal again, get another bearing, and then go to a third spot and do the same thing again.” So, one must take three bearings to estimate one location for one animal. 

Data gained this way is useful, but the number of locations you get per animal and their accuracy are both limited. With GPS, the collars communicate with a satellite system. Biologists can program the collar to record the animal’s location several times a day or more. The data is obtained via website, email, or text message.

“We can change the settings on the collar from the comfort of anywhere in the country that has internet access or cell service,” Hildreth says. The collars can even be set to release and fall off, so the animal doesn’t have to be recaptured at the end of the study. 

“You still need to track the animal and get eyes on them for behavioral studies,” says MDC Black Bear/Furbearer Biologist Nate Bowersock, “but movement wise, there’s no longer a need to fly or track from the ground every day, which saves significant personnel time.” 

Because of weight, GPS units for small animals have more limitations than those for animals like elk, bears, eagles, and bobcats. But technology is advancing quickly, and devices with these same real-time tracking capabilities may soon be rendered small enough and light enough for the tiniest songbirds or even butterflies.

At a Glance

Scientists use wildlife-tracking data to determine habitat and resource use, migration and dispersal patterns, survival rates, restoration success, and more.

The type of tracking device depends on the size, shape, and habits of the animal as well as the current technology available. Before devices are approved for use, they undergo testing to make sure they are safe for the animals. With smaller animals, the weight of the battery is often the limiting factor.

To track otters, a small VHF device needs to be implanted under the skin because otters remove devices attached to the outside of their body. 

Radio tags for brown-headed nuthatches need to be so small and light, the tiny batteries last only a month or two.