CWD Infects Bucks Twice the Rate of Does

The rate of CWD infection continues to increase in Wisconsin’s deer herd.  Whitetail bucks 2.5 years old and up have a higher rate of infection according to the most recent sampling.

Statewide in 2014 5,400 deer were sampled for CWD.  324 deer were found CWD positive mostly in Wisconsin’s southern endemic area this is a 6% infection rate.

The infected deer by age and sex-

• 25% – adult male white-tailed deer (2.5+ years-old)
•   8% –  yearling males
• 10% – adult female deer
•   7% – yearling females

Since the beginning of sampling in 2002 CWD infection have continued to increase mainly among bucks 2.5 years and older.  The best hypothesis regarding the spread of CWD is that it is spread via body fluids containing the prion.  Many researchers believe this is due to the natural behavior of the adult buck.

• Creating and maintaining  scrapes,
• Licking branches to leave a scent that is then licked by other bucks and some does.
• Adult bucks wander a wider geographic area which risks spreading CWD to new areas.

So far, research indicates the best thing to do to contain or at least slow CWD’s  progress is reduce the herd density while removing as many 2.5-year-old bucks as possible. The problem with implementing this strategy is hunter opposition. During the last couple of decades, hunters have come to believe they should let small bucks pass in order to grow them up for bigger antlers, referred to as Quality Deer Management  (QDM).  When CWD was first discovered in Wisconsin, the DNR set in motion a deer extermination policy in the believe they could eliminate all CWD-infected deer in what has become known as the CWD Zone.   During this failed effort a system known as Earn a Buck (EAB) was instituted.  However, according to the documented infection rates an Earn a Doe (EAD) should have implemented instead.  Assuming the infection rates by age and sex above it makes more sense to push down the buck population. A lower population of bucks may keep bucks in the area.  When bucks become crowded in an area, some move-out or are pushed out by dominate bucks.  Causing a certain number of bucks, some which could be infected to move on and infect new areas.

According to Tami Ryan, DNR wildlife health section chief.

“Long-term monitoring of disease patterns is crucial in understanding the dynamics of this CWD, and it’s also important to make sure we keep the public informed, prevalence continues to increase within the department’s long-term monitoring area in Southwest Wisconsin, and remains higher in males than females and higher in adults than yearlings.”

“The department is very grateful for the cooperation that hunters and landowners have provided over 13 years of sampling, they are helping monitor the health of Wisconsin’s deer herds and providing information that is of interest to many.”

WDNR statements regarding CWD monitoring.

Monitoring efforts also included ongoing surveillance within a 10-mile radius of the each new positive found in 2012 in Juneau, Adams and Portage counties in central Wisconsin. Four additional positives were found in 2013 in Adams and Portage counties, while two additional positives were discovered in Adams County in 2014.

Surveillance was also conducted surrounding a CWD-positive captive deer farm in Marathon County, with no wild CWD deer detected.

Following the 2012 discovery of a CWD-positive adult doe near Shell Lake, 2014 marked the third year of surveillance efforts in Washburn County in Northwest Wisconsin. Following recommendations from a local community action team, local landowners and hunters helped the department sample more than 1,900 deer in the area over the last three years. No new positives have been detected. Based on three years of sampling, all information has indicated CWD is not widespread in the Washburn area, and occurs at a very low prevalence rate.