Capture-and-Collar Deer Study Collecting Valuable Survival Data

Ongoing study is tracking 260 deer in northeastern South Dakota

A helicopter crew specializing in animal retrieval was contracted by the state Game, Fish and Parks Department to assist with capturing and radio-collaring whitetail deer as part of a mortality study. Courtesy photo by GFP

For the last few years the South Dakota Game, Fish and Parks Department has been capturing and fitting whitetail deer from local herds with radio collars as part of a statewide study on deer mortality.

“We started in northeast Brown County where we first captured adult deer in winter 2015, and later that spring we captured fawns for the study,” said Nick Markl, a resource biologist based out of the Webster GFP office. “In 2016 we expanded that study area, which we call a data analysis unit or DAU. We call this particular unit DAU-9, and it now includes parts of Brown, Spink, McPherson, Edmunds and Faulk counties.”

Markl said 150 additional deer were captured and collared within the unit earlier this year, bringing the four-year total to upwards of 550.

“We’ve identified some wintering herds in the unit and spread the collars out when we did the capturing,” Markl said. “We wanted to get a better, more widespread sample to get an accurate representation of the entire herd.”

Tracking deer

Deer of various age classes — adults, juveniles and fawns — have been collared as part of the study.

“We do this to figure out survival rates at each stage of a deer’s life,” said Alex Elias, wildlife damage specialist. “After we collar the deer we monitor them once a month with radio telemetry equipment. Each individual deer collar has its own frequency that is unique to that specific deer. Monitoring is done from an airplane with an antenna attached to the strut of each wing. This method allows us to hear signals from the collars at farther distances and track all the deer quickly.”

Markl said that of the 550 deer that have been collared so far, there are currently about 260 deer with active collars. He said GFP staff can usually track down all the specific radio-collar signals in one or two days from the airplane.

“If we plug in an individual deer’s frequency, it’s only going to be one of two signals — an alive or mortality signal. If it’s alive, we record it as such and move on to the next signal. If it’s a mortality signal, we’ll ask the pilot to slow down and decrease altitude and try to get the location pinned down as close as we can. From there, we go in on the ground.”

Elias said handheld telemetry equipment similar to what’s used in the plane helps GFP staff find the final location of the collars. If the collar is on private land, GFP obtains landowner permission before retrieving the collar.

“After permission is obtained and the collar is located, we use evidence at the scene to determine the fate of the deer,” Elias said. “We look for bones, hide or other deer parts in the area, as well as look at the collar for additional evidence of what happened. Did the deer die or did the collar simply tear or fall off? Collars have been found in some pretty strange places. I have found them in sloughs, under the ice of a recently frozen pond, and even around coyote and fox dens.”

Markl said hopes are that collars for adult does last the lifetime of the deer, while collars for fawns and juvenile deer — deer he said were not quite a year old at the time of capture — should fall off by design in a year or two as they mature.

Both Markl and Elias said hunters should not base their decision to kill a deer on whether it has a collar.

“Hunter harvest is part of the mortality we look at in these studies, so what we tell hunters is to treat these animals like the collar isn’t there,” Markl said. “We have some harvested every year, and that’s part of the data we’re looking to collect.”

Moving forward

Markl said this was the last year that deer in the five-county study area would be collared.

“This is the last year of captures, so now for the next two years we’ll only track the deer we have left until our sample size falls below what we need for that unit,” he said.

However, Markl said this was the first year deer in another study area in northeastern South Dakota were collared as part of the statewide survey.

“We actually just started collaring deer in DAU-10, which is basically everything east of Aberdeen,” he said. “That unit includes Day, Marshall, Roberts, Grant, Clark, Codington, Hamlin and Deuel counties. So far in 2018 we’ve collared 107 adult does and 110 male and female juvenile deer in that unit.”

Gathering deer mortality and survival information from various study areas across the state will ultimately help GFP gain a better grasp on population trends and aid in future management decisions, Markl said.

“This data is another tool for us to use in our management meetings,” he said. “These survival rates help us determine if the deer population is increasing, decreasing or stable, and will allow us to use some sound scientific data to determine tag allocations moving forward.”

Previously, Markl said state wildlife officials relied more heavily on anecdotal evidence. That included population estimates from GFP staff and hunters, harvest data and the annual fall classification surveys, which primarily focus on fawns throughout the summer and early fall months within a data analysis unit. He said the data should help wildlife officials better predict population trends and hopefully avoid drastic differences in the number of deer licenses and tag allocations available on a year-to-year basis.

“In the past we’ve looked at deer populations in the current year, where we were kind of following that roller coaster every year where if there were more deer we had more tags, and fewer deer meant fewer tags,” he said. “With this population model we hope to gain foresight and adjust accordingly ahead of time.”

Follow @OutdoorForumMag on Twitter.