INNER WORKINGS

SMART collars help track and conserve wildlifeLeslie Willoughby, Science Writer

Caleb Bryce drops into a ravine and tucks into theshadows. The dry foliage bursts into confetti as apuma careens up the opposite bank, hounds wailingclose behind. Bryce and other scientists leap inpursuit. The big cat skirts a meadow and vaults intoa fir tree. Wide-eyed, she pants as saliva streams fromher jaw. When a shot hits its mark, the puma jumps toground and streaks away.

This heated chase is part of efforts to tranquilizeand study pumas. As the animals continue to encroachon towns and cities, there’s an urgent need to under-stand their movements and behavior. In essence, sci-entists want to know what it takes for a large mammalto survive in a landscape shared more and more withpeople. To find out, they developed collars that domuch more than pinpoint animal locations: they alsotrack a complex suite of movements and measure en-ergy expenditure. Their findings, and these seemingly

simple collar advances, could help better conservewildlife and protect humans worldwide.

For decades, GPS tracking collars have revealed ananimal’s location, indicating the distance traveled be-tween position readings, but not whether the animalmoved directly or took side trips. And GPS collarsalone don’t indicate whether the animal ran or walkedfrom point to point. These behaviors affect the energyan animal expends, which can be crucial to predictingand protecting its range. Species Movement, Acceler-ation, and Radio Tracking collars—SMART collars—aren’t a conservation panacea, but they’re proving tobe a crucial tool in multiple arenas.

Getting SMARTerIn 2014 eco-physiologist Terrie Williams, wildlifeecologist Christopher Wilmers, and computer engi-neer Gabriel Elkaim of the University of California,Santa Cruz (UCSC), designed and developed SMART

SMART collars record an expanded suite of data compare with GPS collars, providing a potentially important tool for con-serving wildlife and minimizing clashes with people. Image courtesy of Sebastian Kennerknecht (www.pumapix.com).

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collars. They equipped the collars with GPS, added amagnetometer to estimate heading, and incorporatedaccelerometers to show motion. The team becamethe first to measure energy expenditure using thesecollars on a large terrestrial cat (1).

The accelerometer records a collar’s full range ofmotion along three axes—back and forth, up anddown, side-to-side—as often as 32 times per second.These data signatures show how fast a wild animalmoves, how high it jumps, when it rests, walks, andeats, and how it kills its prey. Such details provide anaccurate picture of an animal’s total energy expendi-ture over an entire season. And that total indicates thedimensions of habitat an animal needs to obtainenough calories to reproduce and, ultimately, survive.

“The collar reflects the behavioral repertoire andgenerates a unique signature for a behavior,” explainsBryce, a doctoral candidate in ecology and evolu-tionary biology at UCSC. These advancements haveopened a newwindow on behavior patterns of all sortsof big mammals, including pumas.

In 2011, Wilmers and other scientists with the SantaCruz Puma Project sought to correlate locations withbehaviors (2). A traditional GPS/radio telemetry collarhelped them determine where pumas fed, moved,communicated with each other, and raised their kit-tens. The researchers plotted these behaviors ontomaps and compared the locations with sites of humanconcentration. Their findings: pumas hunt and feedrelatively close to humans, even within 150 meters.But females need at least a 600-meter buffer fromhumans to communicate with males and successfullyraise kittens.

When GPS signals showed that a puma hadremained at the same location for hours, researchersknew it must be sleeping or feeding. Then they visitedthe spot and searched for remains of prey. Althoughpumas kill many deer, Wilmers says, they also prey ona fair number of raccoons and domestic cats, as well asthe occasional skunk. “People are the only animalwe’ve seen that deters pumas,” he says.

Using the SMART collars, UCSC researchers addedanother crucial layer of data (1). They found that ahunting puma moves constantly. It turns off-course, jogsthrough meadows, and zigzags up rocky outcroppings.These behaviors expend more than twice the energyexpected simply by traversing rugged terrain. Pumasmake up for this exertion by stalking prey quietly andlying in wait, sometimes for more than 30 minutes. Afterconserving the energy required to land and then subduetheir prey, pumas expend the exact effort required to kill:a small pounce for a fawn, a big one for a buck.

The collars and environmental sensing devices areproviding information that supports conservation andpractical management practices (3). By controllingdeer populations, for example, pumas help reduce theincidence of disease and starvation that would beexperienced by a larger, less well-nourished herd, saysfield biologist Paul Houghtaling, who manages thepuma project.

Findings have even translated into policy action.Data from collars helped researchers identify puma

pathways over State Route 17 in the Santa CruzMountains, including a crossing point that accountsfor 40% of all vehicle/wildlife collisions. In November,voters approved a tax for transportation projects thatincluded $5 million to build a conduit at that deadlycrossing point to protect drivers and wildlife.

Careful CorrelationEven so, SMART collars have drawbacks. Eight monthsof Bryce’s research readings, taken at the rate of 32per second, have added up to terabytes of data andrequire supercomputers for analysis, he says. Scien-tists have resorted to various means to interpret such

massive datasets, aiming to identify animal energyexpenditure and associated behaviors (4–6).

And although the collars’ accelerometer data pro-vide a proxy for energy expenditure, that doesn’tnecessarily reveal what exactly the animals are doing.Is energy being spent on hunting or escaping? “Toget at energetics, you have to correlate the acceler-ometer data to experimental trials,” says Wilmers.

To do so, Williams and her team engage in an in-tensive laboratory-to-field analysis. In the laboratory,they measure the oxygen consumed by captive ani-mals wearing a SMART collar; then they calibratethose measurements to readings from the acceler-ometer in the collar. While slowing or speeding atreadmill on which the animals trot, they measure

The collars, attachedwhen the animals are tranquilized, include an accelerometer thatrecords the animal’s full range of motion as often as 32 times per second. Datasignatures indicate, among other things, how fast it moves, how high it jumps, whenit rests, and how it kills its prey.

“You can’t help wanting to preserve them when youknow the intimate details of their lives.”

—Terrie Williams

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oxygen consumption, a proxy for energy expenditure.At the same time, the researchers calibrate behaviors,such as walking or running, with distinct accelerome-ter readings or signatures.

The team verifies and fine-tunes associations byobserving a captive, collared animal while it roamswithin an outdoor enclosure. Later, they correlate theacceleration signatures of the captive animals withthose generated by wild ones in the field. Finally,Bryce and others train a computer model to recognizesignal patterns they have associated with directly ob-served behaviors. A big spike may be a pounce,for example.

Widespread ApplicationsPumas aren’t the only animals donning the collars. Tostudy lions in Laikipia County in Kenya, Williams andWilmers joined forces with conservation biologist Lau-rence Frank at the University of California, Berkeley.The lions that live within national park boundaries,Frank says, are incredibly tame. But outside suchprotected areas—where lions live among people, prey

on livestock, and get killed as a result—they’re skittish.“Even with traditional radio collars we knew very littleabout howmany were in a group and who goes aroundwith whom, and how often do they encounter com-peting lions,” he says. The new collars have “opened aview into the behavior of these shy, unapproachableanimals we’ve never had, compared to 20 years of re-search previously,” says Frank.

Data from collars revealed when and where the bigcats hunt, sleep, encounter competition—and die. Theteam honed in on each bout of a fatal fight betweentwo collared lions, virtually second to second. That ledWilliams to study how remote accelerometer signalsprovide information about the cause of a lion’s death:for example, when competing lions’ ranges overlap.

The technology, notes Williams, has shown us justhow far polar bears are now having to swim with Arcticice disappearing (7), and even how narwhals anddolphins are dealing with oceanic noise. “You can’thelp wanting to preserve them,” Williams says ofpumas and other collared animals, “when you knowthe intimate details of their lives.”

1 Williams TM, et al. (2014) Mammalian energetics. Instantaneous energetics of puma kills reveal advantage of felid sneak attacks.Science 346(6205):81–85.

2 Wilmers CC, et al. (2013) Scale dependent behavioral responses to human development by a large predator, the puma. PLoS One 8(4):e60590.

3 Wilson AD, Wikelski M, Wilson RP, Cooke SJ (2015) Utility of biological sensor tags in animal conservation. Conserv Biol 29(4):1065–1075.

4 Dewhirst OP, et al. (2016) Improving the accuracy of estimates of animal path and travel distance using GPS drift-corrected deadreckoning. Ecol Evol 6(17):6210–6222.

5 McClune DW, et al. (2014) Tri-axial accelerometers quantify behavior in the Eurasian badger (Melees meles): Towards an automatedinterpretation of field data. Anim Biotelem 2:1–6.

6 Walker JS, et al. (2015) Prying into the intimate secrets of animal lives; software beyond hardware for comprehensive annotation in‘Daily Diary’ tags. Mov Ecol 3(1):29.

7 Pagano AM, et al. (2017) Using tri-axial accelerometers to identify wild polar bear behaviors. Endanger Species Res 32:19–33.

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