An ongoing study by the Wisconsin Department of Natural Resources (DNR) that deployed tracking collars on more than 1,200 animals in three counties shows that chronic wasting disease (CWD) is dramatically decreasing the survival of white-tailed deer.
“Reduced female survival lowers the growth rate of the population, and when sufficiently suppressed, may result in population decline,” the DNR said yesterday in a news release. “Specifically, results from this study indicate that when the CWD prevalence rates of females surpasses about 29%, deer populations are expected to begin declining.”
CWD is a fatal neurodegenerative disease of cervids (eg, deer, elk) caused by infectious misfolded proteins called prions. There is no vaccine or treatment. While people have not yet been diagnosed as having CWD, experts fear it could cross the species barrier.
Disease halves survival in does
The DNR launched the Southwest Wisconsin Chronic Wasting Disease (CWD), Deer and Predator Study in fall 2016 to evaluate factors that could affect deer survival and population growth, such as CWD, predation, habitat suitability, and hunter harvest. The researchers call it the largest and most comprehensive deer study ever done in the state.
If CWD continues to spread and its prevalence continues to increase, populations will likely face further declines.
The study was conducted in CWD-prevalent northern Iowa, Dane, and Grant counties, where the disease was first detected in 2002. Among the adult deer, fawns, coyotes, and bobcats captured, 766 adult deer were fitted with GPS collars, and 323 fawns received radio tracking collars.
The researchers calculated that the likelihood of survival from one year to the next among healthy females was 83%, compared with 41% in those with CWD. The respective percentages among uninfected and infected males were 69% and 17%.
“If CWD continues to spread and its prevalence continues to increase, populations will likely face further declines,” they wrote. “The exact degree of these declines, however, will depend on local harvest and recruitment rates.”
The DNR, however, said it doesn’t expect the complete elimination of infected herds from the area, because deer populations can increase reproduction when deer are less abundant due to less competition for food, space, and other resources. Data analysis is ongoing.
