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Southwest Wisconsin CWD, Deer & Predator Study Newsletter

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Issue 9: May, 2019

In this issue of Field Notes, we wrap up our third and most successful adult deer capture season to date. We explore the capture and biopsy processes, and talk to some crew members about their experience in the field this winter. We also feature two more project staff members, Research Scientist Dan Storm and Predator Project Coordinator Alex Hanrahan. Finally, fawning season is here, and shifts are filling fast; don't miss out on this opportunity to participate!

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

Adult Deer Capture: Wrap-up and Results
As our third capture season comes to a close, we look back on all the hard work that went into surpassing our collaring goal for the first time in the history of the project. Watch the video to see our team in action.

Men in field
Behind the Biopsy
It is fairly simple to collect samples from a dead animal, but how do we extract tissue from a living deer? Read all about the science behind the biopsy and what we can learn from the samples we collect.

Staff Profiles
Meet two employees whose hard work helps make this project possible: Deer and Elk Research Scientist Dan Storm and Predator Project Coordinator Alex Hanrahan.

fawn in grass
Fawning Season: Sign Up Today!
Sign up to participate in our annual fawn survey.

Deer Capture Wrap-up and Results

Capturing deer this past winter was a delicate dance in tough conditions: Several drop nets, those mesh traps strung up like a circus big-top, broke their center poles or the ropes holding them under the weight of ice; clover traps froze to the ground; and arctic temperatures posed a threat to fingers and toes.

Despite various challenges, the crew responsible for capturing and collaring deer for the Southwest WI CWD, Deer and Predator project had their third and best season, which ended when the crew caught their last deer of the season on March 20.

Wes Ellarson, project coordinator, said the team collared 216 new deer, plus four whose old collars failed which were fitted with new devices for a total of 220, well over their 200 goal.

The season started off slow with mild temperatures in December. The first deer was collared December 11, but the next wasn’t caught until December 28. Warm weather and a lack of snow meant deer could graze in cornfields and had an easier time overall finding food sources, so they were more likely to avoid the nets.

The mild early-winter weather quickly turned – the crew faced several ice storms through the season, a polar vortex hit around the end of January, snow fell, and then it continued falling through the rest of the winter. There were nights when the wind chill hit 50 degrees below zero (the team won’t trap, however, when temperatures fall this low). A local news report described the polar vortex as the coldest stretch since February, 1996, but cold and snow are good for capturing deer, and these conditions persisted into March.

The team had other factors working in their favor: more landowners participated this season, meaning more acreage on which to capture deer, and more experienced crew returned from the previous year who didn’t need extensive training. Newcomers received several weeks of intense preparation for the field, including training on equipment, traps, data sheets and different situations they might encounter with deer.

“The team definitely grew pretty quickly, which is required by the job. We get a trial by fire—there’s no real way to practice doing fine-tuned work in sub-zero temperatures,” Ellarson said. "It’s kind of a season that hit us really hard, and you try to hang on for the ride, and look back, and (see that) it was good.”

The adult deer capture season is roughly three months, from December to March. Each study area of the project, an east and west side, needed to catch on average three deer a day to meet their quota. “At one point, one side captured like 20 deer in two days and 40 deer in a week. It was crazy. We’d have four or five caught in the morning and six or eight (at night) in drop nets pretty regularly,” he said.

Ellarson said the team has continued to evolve to meet challenges. Last year, they rigged a remote trigger on drop nets so the crew didn’t have to sit outside in a blind waiting for deer to come under the net, they could sit in a truck instead. This also increased their chances of success by confining their scent and reducing noise. This year, they borrowed a snowmobile to get around in deep snow and redesigned their drug coolers to better protect the contents from extreme temperatures.

Trevor Johannes, an assistant crew leader on the east side, said he had some tricks for dealing with tough conditions, such as hand warmers. Some of the work that was conducted on the deer, such as collecting a rectal tissue sample, required fine-motor skills and unfrozen fingertips, so he layered up, he said.

Johannes was in his second year on the project and was promoted to assistant crew leader, with seven technicians reporting to him. He and crew leader Samantha Bundick discovered each other’s strengths and weaknesses early and capitalized on this knowledge to keep the project on track. “I think Sam is really good at organizing and planning and looking at the big picture. I really like to examine the situation…I’ll critique certain things,” he said. They were able to capture deer more efficiently working together. And that sentiment sums up the whole project, he said.

“This is not a one-man operation. Without everyone (working together), the project and our successes couldn’t have been possible,” he said.

After the season ended, the team cleaned, inventoried supplies, put away winter gear and prepared for fawning season. And in the fall, they’ll prepare to do it all over again for their fourth and last season.

Behind the Biopsy

men in field

Study crew works on deer

The Wisconsin DNR’s Southwest CWD, Deer and Predator study seeks to evaluate the extent to which Chronic Wasting Disease impacts Wisconsin’s deer population. To that end, researchers need to have a clear picture of how well CWD-infected deer survive compared to those who are not infected. Determining the CWD status of each deer we collar is vital to making this comparison, but with current technology, this information can only be ascertained through a tissue sample. As most deer hunters know, we can easily extract tissue samples from dead deer, but how do we retrieve samples from an animal that is still alive?

In order to effectively test a living organism for infection, we first have to understand where a disease lives in the body. The mechanism for infection in CWD is a prion. A prion is an improperly folded protein and is the culprit behind a host of neurodegenerative diseases that affect humans and animals alike, including some cases of dementia and the infamous Mad Cow disease. Prions accumulate in the lymphatic system, a vascular network that spans the entire body and is responsible for the transport of white blood cells, or lymphocytes, which fight infection. We are all familiar with how our lymph nodes swell when we get sick – these are the spots in deer where CWD prions appear in the highest concentrations.

This table shows results from the rectal biopsy testing for CWD on live deer captured during the 2019 winter deer collaring. “Not-detected” means that no prions were found in the lymph follicles in the tissue sample submitted for that deer. “Positive” means prions were detected, and it is confirmed that these deer are CWD-infected. “Prevalence” is simply the percentage of our deer in each sex and age-class that had a positive test result.

When it comes to sampling a dead deer for CWD, biopsies are usually extracted from the retropharyngeal lymph nodes, located in the general vicinity of the head and throat. These lymph nodes are inaccessible in deer while they are alive, an obstacle which researchers in the past have attempted to overcome by taking biopsies from the tonsils instead. However, a biopsy of this nature requires extensive training and is an invasive procedure that poses a number of risks for the animal. Lymph tissue is also found elsewhere in the body, including at the end of the rectum. Researchers in the Southwest WI CWD, Deer and Predator study target this area instead, as it is more easily accessible and still provides reliable results.

The process behind a rectal biopsy is fairly benign. Deer are anesthetized prior to the procedure, so they are unconscious for the duration. A topical anesthetic called lidocaine is applied to the area as well, to minimize pain when the biopsy is complete and the general anesthetic used on capture is reversed. The amount of tissue extracted is equivalent to the size of a penny. There is minimal bleeding and researchers have yet to observe incomplete healing or other complications as a result of the biopsy.

Once we’ve obtained a biopsy, the sample is tested using the same laboratory methods used for testing retropharyngeal lymphatic tissue in dead deer. There are a few instances in which this test is not 100% reliable – occasionally, when deer are in the early stages of infection, the test fails to detect the presence of CWD. However, the test is extremely reliable in detecting middle-to-late stage infections. The imperfect detection of CWD through rectal lymph tissue is not an obstacle to meeting our project objectives. Nearly all the deer we capture are tested both before and after death, and some are live-tested more than once, so we do not rely on a single test to determine CWD-infection in most deer. Additionally, we incorporate previously published estimates of false-negative rates into our analysis.

Tissue sampling is also sometimes affected by the genetics of the deer in question, which may account for problems in detecting early-stage CWD in select deer. The rectal biopsy has been shown to be effective in determining the CWD status of deer who have the most common genetic make-up, regardless of the stage of the infection. Stay tuned for a future edition of Field Notes where we cover the interplay between CWD and deer genetics.

While the rectal biopsy is an important part of the Southwest WI CWD, Deer and Predator study, we still use the retropharyngeal biopsy on animals after death. We are continually working with researchers to find less invasive ways to detect CWD in live animals, but we believe the rectal biopsy is the best option for now. It is an effective procedure that allows us to conduct our work safely and humanely, without causing undue stress. Staff are well trained and are given ample opportunity to practice the biopsy on dead deer so that they are properly equipped to conduct the procedure in the field. Once we know the CWD status of a collared deer, we can determine whether CWD poses a significant impediment to its survival. Each biopsy improves our understanding of how this disease affects our deer population, and how it stands to do so down the road.

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Staff Profiles

We’re pleased to feature in this edition of Field Notes two invaluable members of our project staff, Dan Storm and Alex Hanrahan.


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2019 Fawn Survey

fawn crew

SWCWDDP crew and fawn

It’s that time of year again! We are headed out into the woods and fields of southwest Wisconsin in search of fawns to collar as part of our fawn mortality study. Our goal is to collar 100 fawns, and we can’t do it without your help.

This year, we are collaring fawns between May 18th and June 5th. We set out every day during the fawn survey, rain or shine, from the Dodgeville DNR Service Station. We have two shifts, one starting at 7:30 AM and another at 1:30 PM.

We welcome all willing and able volunteers. The minimum age to sign up is 12, and minors must be accompanied by an adult.

Sign up to volunteer and join us in the field!

Last revised: Thursday May 16 2019