February 05, 2024
The 46th annual meeting of the Southeast Deer Study Group was hosted by the Wildlife and Fisheries Department of Louisiana last February. As always, the top deer researchers, professors, and graduate students were in attendance and presented a number of papers on the latest deer research. And, as always, Bowhunter Magazine was there.
This year, I am also including discussions of some of the many papers presented in Denver at the 4th International CWD Symposium. I believe you will find some of that information interesting.
First, to the Deer Study Group meeting. Alex Jensen, from Clemson University, presented a paper on coyote diets in the Piedmont region of South Carolina. He noted that coyotes eat fawns in early summer — the first few months of a fawn’s life. However, the availability of blackberries and other fruits can impact coyotes’ eating fawns. He found that habitat management to increase blackberries lowered fawn predation by coyotes, especially in the second month after fawns drop. Of course, a lot of fawns have already been eaten by then. One thought to save fawns is to trap coyotes before fawns drop. But this research also showed that almost every coyote eats fawns. You can trap coyotes, but you can’t get them all. There will always be coyotes out there and they will eat fawns.
In Texas, cattle are a big deal. But so are deer. One question answered by a paper presented at the Study was: Does the amount of cattle in a pasture affect deer? The interesting results were that cattle numbers (up to a point) did not affect doe-lactation status, or body mass of does and bucks. However, cattle numbers did affect antler size. As the number of cattle per acre increased, the antler size decreased. Note that this study was done on four South Texas ranches, and other studies show that results vary on other ranches, and the reason is that drought has a huge impact on habitat in that part of Texas.
Texas rains are usually scattered, so you have drought areas, and you have areas that get some rain and impact the habitat. So, the number of cattle may impact antler size on one ranch, but 100 miles away, it may not.
Matthew McDonough and his co-authors at Auburn University assessed how wild pigs affect whitetail deer at the population level. They removed 1,851 pigs over a year and a half and used trail cameras to survey the response of deer populations. They found that removing wild pigs will not increase abundance of deer but could impact camera surveys and hunter satisfaction by increasing the ability to see deer in an area.
I found this next paper very interesting. The usual way CWD prions are found in the field is by surveying where hunters killed CWD-positive deer. If CWD-positive deer are killed in an area, then there are CWD prions there from the feces.
Miranda Huang, of the Mississippi State University Deer Lab, has found another way to determine if deer living in an area have CWD. She checked 98 scrapes for CWD prions in an area of southern Tennessee that had a high prevalence for CWD in deer. She found that 54 of them (55%) had CWD prions in the scrape soil. She also clipped the ends of twigs on overhanging branches at the scrape where deer lick, leaving saliva on the twigs. Thirty-five percent of the overhanging limbs at the 98 scrapes had CWD prions. She concluded that deer scrape sites might serve as environmental sentinels to identify CWD present in an area, without relying on harvested deer. What isn’t known is the percent of does and bucks that visit those scrapes that don’t have CWD but get the disease from a visit. We know the prions are there, but we don’t know the impact they have on other deer that come to the scrape.
Another CWD study examined possible prion transfer from deer carcasses that had CWD and were left in the field. A captive deer farm where CWD was found had been depositing (illegally) dead deer carcasses at a site. They found that 14 of 56 carcass samples had prions, as did fly larvae associated with those carcasses. My thoughts are that knowing that prions can be found on fly larvae is just another factor among many that makes eradication of CWD extremely unlikely.
New technology continually changes research methods on deer studies, just as it changes almost everything we do in our life. Heat sensors mounted on helicopters and low-flying planes have been used to census deer, but one recent study utilized thermal drones to survey deer.
In one 6,000-acre, high-fenced area in East Texas, thermal-drone surveys estimated 255 deer, while traditional camera surveys yielded 267 deer. These results suggested that thermal-drone surveys were a viable method for estimating deer abundance and closely compare to traditional ground-based camera survey estimates. But both methods likely underestimated the true population.
The 4th International CWD Symposium yielded lots of new information on CWD from papers presented by 50 speakers and an additional 84 poster displays. One presentation focused on the use of dogs to detect an odor in deer that have CWD. The researchers found that dogs (sample size was six dogs) can detect CWD prions in fecal samples from CWD-positive deer. The dogs could also detect prions from small intestine tissue of CWD-positive deer. The researchers believe that this means there is the potential for dogs to detect CWD by smelling the whole body of a deer — dead or alive. That potential will require further research to confirm whether it will work.
It appears we will always have speculation on whether humans can get CWD from eating animals such as deer or elk that have CWD. Several speakers addressed this question.
One long-term study done by the Center for Disease Control, looked at death rates for human prion diseases (e.g. Creutzfeldt Jakobs Disease) in Colorado, Wyoming, and Wisconsin — all hotbed states for CWD. Even though thousands have consumed CWD-infected venison in those states, the rates for human-prion diseases were similar to other parts of the country, even after many years. The Wisconsin study questioned 642 hunters who have eaten CWD-positive venison over the past 20 years, and none had a prion disease.
As you know, there are no known natural cases of CWD transmission to humans, and we have learned that CWD prions have been found in a number of non-cervid species. This means that a variety of animals that humans consume around the world, other than deer, carry CWD prions.
One study at the CWD Symposium reported on research done where different processed meats derived from a CWD-positive, free-ranging elk were analyzed. The products included filets, sausages, boneless steaks, burgers, ham steaks, seasoned chili meats, and spiced meats. All of those products contained CWD prions. They also grilled and boiled the various meat products and found that the meat still had prion particles, even after cooking. When it was all said and done, the Symposium presenters had significant concern that transmission to humans could occur through ingestion of contaminated meat products, even though it has yet to happen.
Deer and elk can get CWD prions from contact with infected animals or through contact with environmental prions, such as those resulting from decomposition of infected carcasses. Scavengers, such as bobcats, that eat infected carcasses may become vectors for CWD.
In a study done at the University of Wyoming, ground beef that contained cut-up lymph nodes from a CWD-positive elk, were fed to three captive bobcats. In other words, the bobcats were fed elk meat with prions in it. When examining the scats from those bobcats, they only recovered less than two percent of the CWD prions, indicating that bobcats do not pass such prions on into the environment (at least, not many). This doesn’t mean that bobcats kill the prions in their gut, it just means that they sequester them in their body rather than pass them in scats into the environment.
Another researcher at the National Institute of Allergy and Infectious Diseases in Montana fed CWD-infected ground meat from mule deer to a captive mountain lion. They found that only 2.8% to 3.9% of the infected prions were passed by the mountain lion. In fact, prions were only found in the first scats the cat passed, meaning that either the prions were eliminated, or they became sequestered in the lion and did not get dispersed into the environment. Thus, the results of these two “cat” studies were basically the same.
As you can see, between the Deer Study Group meeting and the CWD Symposium, there was a lot of information presented on CWD. As for the upcoming 47th Southeast Deer Study Group meeting, it will be held in later this month in my home state of West Virginia, so you know that I’ll be there!