When it comes to technology, smaller is better. But size is dependent on power—a pocket-size computer is possible because the battery can be recharged.
For scientists working in the field, recharging isn’t an option. Their equipment has to be powered by big, bulky batteries that will stay charged for a long time, maybe even years.
Such is the case for the collars used to track cougars and other wildlife.
Jeff Sikich is a biologist with the National Park Service, which has been studying mountain lions in the Santa Monica Mountains for the past 16 years. He said he’s often asked why the tracking collars have to be so big.
“The collar is doing many things. There’s a battery on the bottom of it, that’s what appears to be large, and then there’s two antennae on the top part,” Sikich said. “Basically, the battery size determines how many GPS locations we can take per collar. Larger batteries mean we don’t have to capture the animals as frequently.”
Even with a sizable battery pack, the collars don’t transmit data 24/7. Sikich said the collars, which cost about $5,000 each, send out eight location readings each day, but that can be changed. If an animal approaches a population center, it can be tracked more closely, but it’s a trade-off—more readings mean more drain on the battery.
Sikich said a battery pack is the main obstacle to having a less obtrusive tracking device. A tracker beneath the skin would be less cumbersome, but the battery wouldn’t last nearly as long, and it wouldn’t be able to transmit all the information the collars do.
In addition to GPS data, the collars transmit a very high frequency (VHF) signal that can be used to pinpoint the animal’s exact location when researchers have to recapture it.
Also, if a collar hasn’t moved for a long time, Sikich will receive a notification on his cellphone telling him as much. In those cases, it usually means the animal has died. The collar could also have fallen off, but Sikich said that’s uncommon.
“All the location data we get allows us to study many aspects of their ecology and behavior. We learn things, including the size of their home range, how they use the landscape,” Sikich said. “We look at survival, mortality causes. We’re interested in reproduction, intraspecific interactions, so how are lions interacting with each other? We look at their food habits and, most importantly, their movement patterns relevant to road development.”
Researchers are aware of the potential for the collar to be a burden on the animal. Sikich said a tracking collar typically weighs between 1 and 3 percent of the animal’s body weight.
The collars are made of polyurethane, which is lightweight and resistant to water and ultraviolet light damage. The edges are flared so the collar doesn’t press into the animal’s skin.
On average, the collars have to be replaced every 18 months. Sikich and other researchers use the VHF signal to find the animal, tranquilize it and put on the new collar. If they can’t find the mountain lion, the old collar will eventually fall off.
“A magnet and a pin will release and the collar will fall off the animal. We also place these cotton rot-away devices on the collar that rot away with time, anywhere from two to three years, in case the magnetic drop-off didn’t work,” Sikich said.
Biologists have used radio collars for decades. Researchers gather a wealth of data from watching an animal’s movements. In the Santa Monica Mountains, where mountain lions risk their lives crossing a roadway, understanding their behavior is key to keeping the population alive, Sikich said.
“I like to think of these animals we’re following as ambassadors for the species in our area,” he said.