With around 384,000 deer and 280,00 elk scattered across Colorado, and the latter capable of traveling 20 to 100 miles during migration, tracking these animals is of great importance to researchers. But it proves to be a challenging task due to the harsh weather conditions and growth changes faced by current GPS tracking collars.
Colorado State University’s Orthopaedic Bioengineering Research Laboratory has partnered with Colorado Parks and Wildlife to develop new tracking collars capable of dropping off animals with a new biodegradable attachment.
“So the idea is to develop something that comes off when it needs to for the animals’ health and safety,” OBRL Associate Director Kirk McGilvray said. “Then (it) also just comes off before the battery dies, so (researchers) can go pick it up and get data off of it and reuse it later down the road.”
As Colorado Parks and Wildlife Field Capture Technician Ian Smith explained, these collars are utilized across the state to track a variety of large game species for research projects and monitoring efforts.
“We have to monitor populations to make sure populations stay healthy and are at levels that our biologists want them to be active,” Smith said. “So part of that is getting GPS collars on animals to track movements, be able to find herds and count individuals and count sex ratios.”
Most current GPS collars deployed across the United States function off a mechanical timed-release system, where a release is pre-programmed to occur at a specific time by researchers.
“It’s … a mechanical piece … that can actually get a signal for a researcher sitting at their computer far away (that) can tell these collars, ‘Hey, I want you to fall on this date,’” Smith said.
Once the mechanical mechanism is released through satellite transmission, the researchers have to retrieve the collar manually, a process that can often take several weeks to months depending on the local topography and remoteness.
“The idea is, can we have something where we can predictably drop these units off, either drop the whole collar off, or drop the sensor off once, once we run its course.” -George Wittemyer, CSU professor and researcher
Keeping this factor in mind, to construct their breakaway points, OBRL researchers landed on utilizing biopolymers, a group of large scale monomers that form together into chains of polymers. Produced by the cells of living organisms, their structures are capable of being biodegraded in the natural environment.
“(Polycaprolactone) was used because we know it has a pretty good degradation rate,” said Sam Winston, a mechanical engineering doctoral candidate and OBRL graduate research assistant.
Crafted through 3D printing, polycaprolactone was selected as the material for the breakaway points due to its two-year natural degradation rate and high tensile strength. To test the biodegradability of the material, McGilvray and Winston developed a testing environment to expedite naturally occurring conditions.
“We developed a system to simulate outside but (at) a high speed so it would simulate six months outdoors in three weeks,” McGilvray said. “So we developed a system to do that, and then we tested a variety of these polymers, and then landed on one that we liked and met the criteria of the client.”
Through a combination of hydrolysis and UV exposure, the team has engineered the connection’s thickness to break down over two years, without direct control from researchers. This eliminates the chance of mechanical detachment failure, guaranteeing all animals will eventually lose their collars.
“We make them a certain thickness, (and) we make them a certain architecture,” McGilvray said. “Then (after) two years (of) exposure to sun and rain and sweat and all those things, they become so brittle that the animal, when it’s walking around, it just shakes them off, and they break off and fall to the ground.”
The collars are currently being tested on animals at Colorado Parks and Wildlife’s Foothill Wildlife Research Facility. While the field study is underway, the results will allow the developers to gather further data about the deterioration process.
“Once some of the weak links start breaking on the collars that are already deployed here, we’ll start getting a better idea of actually how fast they degrade and break when they’re actually on an animal,” Smith said.
After deploying the collars, OBRL was connected by CPW by George Wittemyer, a professor in the department of fish, wildlife and conservation biology. His laboratory focuses on biodiversity conservation issues, including a current venture to track African elephant communication using GPS tracking collars.
Wittemyer was also drawn to the drop-off mechanism due to possible application on animals that are often difficult to capture, release and retag.
“The idea is, can we have something where we can predictably drop these units off, either drop the whole collar off or drop the sensor off once, once we run its course,” Wittemyer said. “This will reduce the stress on the animal, save a lot of expense and a lot of effort of trying to recapture the animal, and it allows us to get our data in a timely fashion.”
OBRL is actively working with Wittemyer to develop a metal-based release component capable of withstanding elephant’s brute force — a prime example of what can be born from collaborative effort across several departments.
“It’s just fantastic,” Wittemyer said. “When these collaborations can come together on campus, you get these different expertises and different needs, and you can actually solve some relatively advanced problems.”
Reach Katie Fisher at science@collegian.com or on social media @RMCollegian.
