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Southwest Wisconsin CWD, Deer & Predator Study Newsletter

Issue 5: April, 2018

We’ve wrapped up another adult deer capture season, and fawn collaring is almost here. In this issue, we look at our deer handling process and how our partners help make this study possible. Then we take another look back at year one data, this time digging into harvest rates. And finally, our field crew gives an update on our adult deer capture results.

Click the titles below to read this issue’s full articles and view our videos.

There’s a Deer in the Net! Now What? [VIDEO]
Our top priority is the health and safety of the deer and our crew. We’re also out to gather high-quality data. Find out how we handle deer, collar them and take CWD samples.
Strong Partnerships Make Study Possible
What happens to CWD samples once they leave the field? And how do we measure survival rates? Find out how our partnerships make the huge size and scope of this project possible.
First Look at Year One Harvest Rates
We continue our dive into year-one data. What do the numbers tell us about harvest rates? And why do harvest rates matter for hunters and wildlife managers?
Field Crew Wraps Up Second Adult Capture Season [VIDEO]
We began the winter trapping season in late December with the goal of collaring 200 adult deer. The crew monitored trap lines through mid-March, and we’re pretty pleased with our results!




There's a Deer in the Net! Now What?





Wes Ellarson skidded the UTV to a halt and sprang toward the clover trap, yelling, “Two deer! Two deer!” to the rest of the crew. Matt Hunsaker came running from the second UTV as Wes lifted the door for both of them to dive into the trap with the two does. By the time Lindsay Martinez arrived with the sedation kit seconds later, Wes and Matt had both deer restrained and wearing blindfolds.

Blindfolding helps calm the deer, and it’s one of the first steps of many taken to safeguard animal health during handling. Every time our crew handles an animal—whether it’s a deer, bobcat or coyote—we have two priorities: first, ensure animal and human safety and second, collect high-quality data.

Deer handling really begins in the office, where the crew prepares capture packs for the field. Each pack has identical gear stored in the same compartments, so no matter which crew member grabs the capture pack, they know where to find everything, from extra gloves to the CWD sampling kit. The packs stay well-stocked and equipment that comes in contact with deer bodily fluids is single-use to prevent any risk of spreading CWD between captured deer.

Wes assessed the age and size of both deer: he had a large adult doe, and Matt had a yearling doe. He called the information to Lindsay, who then drew up the appropriate doses of the capture drug for each deer. The capture drug includes both a sedative (calming agent) and an anesthetic (pain reliever). Reaching through the net, Lindsay gave each doe an injection in the right hindquarter. Everyone fell silent. Adrenaline can interfere with the action of the drugs, so excess noise could slow the sedative effect. The crew stood motionless for several minutes, watching for the sign from Matt and Wes that both deer were ready for handling.

Lindsay Martinez prepares a rectal biopsy sample

Meanwhile, Lindsay prepared to take a biopsy from the doe’s rectum to send to the Wisconsin Veterinary Diagnostic Lab for CWD-diagnostics. Because CWD prions accumulate in the lymphatic system, this nickel-sized sample of tissue is enough to test for the disease. Lindsay laid out a sterile pad, swabbed the doe’s rectal area and removed a fecal sample. She then inserted a speculum and turned on her headlamp, making a sterile theater for this procedure in the midst of the capture site. With forceps and a scalpel, she carefully removed the tissue sample and placed it in a ready cassette for transport to the lab.

With the sample taken, Matt unwound a cloth tape and took measurements of the doe’s hind leg, girth and length. He also felt for fatty tissue around her spine to assess her body condition. Matt then used an extractor to pull a tooth from the adult doe for an accurate age estimate. The tooth will be sent to a laboratory which specializes in using cross-sections of teeth to age wild animals. This is akin to how trees are aged by looking at tree rings.

A capture kit unpacked

Before administering the sedative reversal drug, the crew used nets to move both deer several yards away from the capture site and the UTV trail. We do this so that deer have a clear path into the woods and away from our equipment when they wake. With the deer in the nets, the crew used a gambrel and hanging scale to weigh both does. Lindsay prepared and administered the reversal drug and removed the does’ blindfolds. She laid them back over the deer’s eyes, shielding them until they stirred and the blindfolds fell away.

Once again, the crew waited in silence, watching both animals. A few minutes apart, each doe twitched and then within a few seconds, stood, got her bearings and leapt out of site into the woods.

Two crew members weigh a doe fawn while two others take a rectal biopsy from an adult doe.

With a successful capture almost complete, the crew returned to the clover trap. Wes reviewed the field notes taken by Sarah and Matt on each deer. Their drug doses and injection sites were written there along with their body measurements, notes on their biopsy sample, collar frequency and ear tag numbers. Looking down the page, Wes read back a record of the entire capture event, adding in notes on the reversal process.

From start to finish, most handling events take about half an hour. These deer are quickly back to normal (except now carrying some new jewelry and officially enrolled into the SW WI CWD Deer Predator project)! These deer are now giving us valuable information on survival, movements, and habitat use.

With the capture event complete, the crew reset the clover trap and packed away their gear before climbing back into the UTVs and riding off to check the next trap on the line.






Strong Partnerships Make Study Possible



When DNR’s Office of Applied Science (OAS) got the call to launch this project as part of the Governor’s Initiative on CWD, we set out to design the largest and most comprehensive deer study ever undertaken in Wisconsin. Our driving question—does CWD significantly affect deer populations in our study area—turned into an umbrella for a host of other inquiries that need to be addressed if we’re going to find the answer to that big question. We set a high bar for data quality, and we realized some of our questions would need outside expertise if we were going to answer them as rigorously as possible.

First, Dr. Daniel Storm, DNR’s deer and elk research scientist, collaborated with our furbearer and carnivore research scientist, Dr. Nathan Roberts, to design the study. They drew on their experience from past projects and consulted with Wildlife Management to outline a study that could achieve our goals and be of greatest use to the Management program. Most of the work would be done in-house by OAS, but some of it would benefit from collaboration with external partners.

Our crew handles all data collection in the field. They set nets, sit blinds, handle every collared deer and remove biopsy and genetic samples. OAS staff then organize and analyze much of the data we gather. To process our biopsy samples, we chose to work with the Wisconsin Veterinary Diagnostic Laboratory (WVDL), part of UW’s School of Veterinary Medicine. Working with WVDL is more efficient than running the labs ourselves, and we can take advantage of their diagnostic expertise. Having WVDL analyze our samples also guarantees that our CWD results are independently verified.

Our field crew also investigates mortalities any time a collared deer dies. We retrieve the collar and conduct a thorough site investigation for any clues of what may have killed the deer.

A fawn collar found during a mortality investigation. We send investigation findings to Marie Pinkerton, DVM, at the UW School of Veterinary Medicine

Whenever the condition of the remains allows, we remove the deer’s body to the University of Wisconsin Veterinary Hospital’s Department of Pathobiological Sciences, where Dr. Marie Pinkerton, DVM, performs a necropsy, an examination of the deer’s remains similar to an autopsy.

Pinkerton is a clinical associate professor and head of anatomical pathology at the Veterinary School with nearly two decades of experience in wildlife pathology. She said that she enjoys working with deer. “They’ve got so many things that can go on,” she said, “And they’re so important to the state in a variety of ways.”

Pinkerton sends a sample of spinal tissue to the WVDL for postmortem CWD testing, and she examines every organ system for clues that could lead to cause of death. Then she examines plated tissue samples under a microscope. “In some cases,” she said, “I might take other samples for bacteria testing or toxics screening. It depends on the case. I have a standard procedure that I can tailor to the case as I go along. It’s kind of like detective work. Each case is a puzzle that I have to figure out.”

Hannah Manninen takes field notes during an adult deer capture event. Field data goes into the survival models used by our partners at UW Madison, USGS, and the Wisconsin Wildlife Cooperative Research Unit.

A wildlife study like this one relies not only on good data collection, it needs rigorous statistical modeling to interpret that data. To look at CWD in the context of forage availability, hunter harvest and depredation, we have to combine data on all these points into one composite model for analysis. With such a huge study scope, statistical modeling for a project this size is a full-time job from the outset.

To complicate things further, statistical models aren’t one-size-fits-all. In fact, tools can vary widely depending on the type of question being asked. For our study, we require the expertise of wildlife statisticians whose work focuses on the analysis and modeling side of the equation. That’s why OAS is working with Dr. Dan Walsh, quantitative ecologist with the U.S. Geological Survey and Dr. Alison Ketz, assistant research scientist in UW-Madison’s Department of Forest and Wildlife Ecology and the Wisconsin Cooperative Wildlife Research Unit.

As a quantitative ecologist, Walsh has many years of experience building and analyzing statistical models for studying wildlife, and he consults with Dan Storm and Ketz on the study’s design and progress. Ketz has taken on the full scope of our statistical framework in collaboration with Storm and Walsh. She has experience designing and analyzing statistical models of elk populations in Colorado and a background in formal statistics.

According to Ketz, “What I love about this job is combining the formal math side with the development of new statistical models. And then I implement those models by writing computer programs, which I actually enjoy doing.”

Statistics aren’t only helpful once the data’s been tabulated. Ketz is also using her statistical acumen to boost our data collection in the field. “This spring,” she said, “I developed a way to take advantage of some machine learning methods to predict when a collared doe is giving birth.” When the crew knows a doe has given birth, they have a better chance of locating and collaring her newborn fawns, bringing them into the study.

A project the size of the Southwest Wisconsin CWD, Deer and Predator Study has a lot of moving parts. Data collection to answer one question happens while we crunch the numbers to answer another. Our partnerships with UW’s Veterinary School and Department of Forest and Wildlife Ecology, with the Wisconsin Cooperative Wildlife Research Unit and with the U.S. Geological Survey keep the project humming. It is a team effort, and we have assembled a great team to ensure our project is successful. In future articles, we’ll explore more about the ins and outs of our work as well as how our partners contribute to our progress. Stay tuned!






First Look at Year-One Harvest Rates



We continue to dig into data from our first year of data collection, all in an effort to keep you in the loop about our study.

In a previous article, we looked at how survival rates differ over the course of a year between collared deer that tested CWD-positive at capture and those that tested negative. We provided a few examples of how CWD-positive deer died, to illustrate how CWD can result in deer death.

Here, we’ll look at survival from a different perspective: harvest rates.

First things first: what does ‘harvest rate’ mean? Every fall, some deer are harvested by hunters, and others are not. Simply put, the harvest rate is the percent chance that an individual deer is harvested by a hunter. When we talk about harvest, we always mean deer legally killed by a hunter and registered with the DNR.

Wildlife managers care about harvest rates for a pretty obvious reason; hunting influences deer populations. Deer managers, including County Deer Advisory Councils in Wisconsin, may want to increase, decrease or stabilize the deer herd. We attempt to achieve these objectives by setting antlerless quotas while allowing hunting opportunity.

Additionally, we’re interested in buck harvest rates because they provide a link between the number of bucks harvested and the total population size. Here is a quick, fictional example to illustrate. Suppose we have a registered harvest of 1,000 bucks. If we estimate that the buck harvest rate is 50% of all bucks in the population, then that means we had 2,000 bucks to start with before hunting began. How it works in practice is more nuanced, but the point is that harvest rates are an important building block in estimating deer populations.

Lastly, the harvest rate is a part of the bigger picture of how CWD might be influencing deer populations and how deer harvest management might be altered to manage CWD or to better manage the deer population in the face of the disease.

How we use harvest rates article

The hunting-season mortality rates we observed during the first year of the Southwest Wisconsin CWD, Deer and Predator Study are quite low. Of the deer that survived to the start of the archery season (September 16), about 14% had been harvested by the end of the final hunting season (January 7). The total mortality rate during the hunting season (harvested by hunters or dead by another cause) was 22%. These sound like straightforward numbers, but there are a few things to keep in mind.

Those are the numbers, but what do they mean? First, keep in mind that the numbers we report from this year combine data from bucks and does. We expect antlered and antlerless deer to have different harvest rates. It’s also likely that older bucks have a higher harvest rate than younger bucks, which are more likely to be passed up by hunters due to their smaller antlers. While these differences likely exist and are important, it’s just too early in the study to get into them; we need more data.

In the future, we’ll also want to distinguish between archery and firearm harvest. We’ll also want to compare harvest rates between CWD-positive and CWD-negative deer as well.

Caveats aside, it looks like harvest rates in the study are quite low. It will be fascinating to see if this trend continues and to contemplate what this means for the deer population in this area of the state with high CWD prevalence.






Field Crew Wraps up Second Adult Deer Capture Season




We knew our adult deer collaring goal was ambitious before the study began when we set the number at 200 deer per year. In 2017, our first year, we skirted February ice storms and thaws and managed to collar 138 deer. We came up short, but since it was our first season and the weather had been so uncooperative , we felt satisfied. With mostly better weather and a more seasoned crew, we trapped 204 deer in 2018, with 194 new collars!

At the close of 2018 capture season, our crew has a running total of 338 deer collared. With two out of four seasons behind us, the field crew met in late March to debrief on what went well and how we can improve to collar even more deer in 2019. Our capture drugs and handling equipment performed well, and the crew settled into a steady rhythm handling deer in the field. Our night vision had underperformed in some instances, so we are investigating the possibility of using thermal imaging when we drop net after dark. The crew’s hands-on experience setting traps, sitting blinds and handling deer is one of this study’s strongest assets, and their insights will set us up to collar hopefully even more deer next winter.

We also have an annual collaring goal of 30 bobcats and 30 coyotes. Within only a few weeks of coyote collaring from late October through early December, we exceeded our quota with 32 coyotes. As ever, bobcats remained more elusive. Beginning in October, our crew collared 14 bobcats. We have local trappers to thank for our early coyote success and our steady increase in bobcat collars. Our totals for the project to date stand at 39 coyotes and 21 bobcats collared.

With adult trapping over, we’re gearing up for fawn collaring. We set a goal of 100 fawns collared. We’ll let you know how we did in the next newsletter!

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Last revised: Thursday May 16 2019