I've included a link below for the CWD study that mentions Wyo deer will go virtually extinct in 41 years.
The sample size of deer captured was 143 which is extremely small. It mentions in the report that the majority of collared deer deaths in this study were from mountain lions and CWD was possibly the 2nd most common cause of death. My guess is that it is difficult to determine if death was truly from CWD or from natural causes (winterkill, drought, poor nutrition/habitat, age, etc.). Death may have been the result of a combination of several factors.
It has been over 10 years since this study was conducted. If deer decline at a rate of -19%/year (as mentioned in the report) there should be a significant decline in the deer population in the study area by 2025?
The report mentions that genotypes play a major role in life expectancy of CWD positive deer. It is possible that deer with desirable DF or FF genes live longer and it's extremely hard to predict if deer with resilient genotypes will live just as long as deer that do not contract CWD.
Generally speaking, deer live short lives and may not contract CWD until they are relatively old. How many
truly sick CWD deer are going to make it through a rough Wyo winter with coyotes and mtn lions on the prowl? It makes sense that over time the poor genetic and sick deer will be replaced by those with the very best genetics in the herd! It would be interesting to know how quickly this actually happens. I imagine there will always be poor genes even in the healthiest environment and herd, but the proportions should change over time. The turnover rate depends on a lot of different factors..... the proportion of DF or FF genes in the herd, predation numbers, winterkill, drought, habitat condition, other diseases, etc. This is a prime example of the old-school conception of "survival of the fittest" and "natural selection."
Habitat condition plays a vital role in fawn recruitment and deer survival. I've been seeing healthy twin fawns born in sites where we've conducted cheatgrass improvement projects in the epi-center of where CWD was first reported here in Colorado since the 1980's.
Yes, CWD has been around for 45+ years, and the deer are doing fantastic on these sites with healthy habitat! According to the report they should be extinct?
Bottom line......Culling operations and harvesting older age class bucks may actually do more harm than good from a genotype standpoint if it is desirable to preserve the best genetic material in the herds.
Here is a link to the entire report. The report also includes info on CWD in deer vs elk.
Chronic Wasting Disease will cause a Wyoming deer herd to go virtually extinct in 41 years, a five-year study predicts.
wyofile.com
Chronic Wasting Disease will cause a Wyoming deer herd to go virtually extinct in 41 years, a five-year study predicts.
The investigation, which relied on the capture of 143 deer, examined the dynamics in the Southern Converse County Mule Deer Herd that lives southwest of Douglas near Laramie Peak. There, a population that once numbered some 14,000 in the early 2000s dwindled to half that size in about a decade.
The Chronic Wasting Disease study is one of only three that have been conducted on wild deer, elk or moose herds, none of which have yet seen print. While wildlife managers have long suspected CWD as a principle agent in the ravaged Converse herd, the study puts numbers on the problem, calculating a 19 percent decline annually.
University of Wyoming doctoral student Melia DeVivo spent four years of fieldwork and another year crunching numbers before defending her PhD thesis on the herd. She calculated the herd would go extinct in 41 years, without taking into account genetic differences that make some deer more resistant to CWD, or accounting for deer migration into the area. Even when taking in those factors, the herd will decline dramatically, she said.
“I estimated that CWD was causing a 19 percent annual reduction in the population, which is pretty significant,” she said. “Potentially, in 41 years, it would be locally extinct.”
The number-one cause of mortality was mountain lions, the study found.
“I was already on the lookout for that,” DeVivo said. “This has also been shown in CWD studies in Colorado. We did see that CWD-positive deer were more susceptible to mountain-lion predation.”
The second leading cause of death was CWD itself.
Genotypes make a difference
Researchers have found that deer with different genes react differently to CWD exposure. The key gene at a location known as codon 225 can have one of three combinations of alleles respectively named SS, SF or FF, DeVivo said. All three are represented in the Converse herd.
The majority of mule deer today are SS, and they get infected at a higher rate, the study showed. “They are 30 times more likely to be CWD-positive compared to deer that had SF or FF,” she said.
Although DeVivo’s mathematical model predicted the herd would go extinct in 41 years, without accounting for genetic variations, that won’t actually happen because new deer are expected to move into the herd’s home range. When accounting for genetic variation, the study predicts the genetic mix of a surviving population will change over time.
“What I found was within a 100-year period we do see a significant increase in those less-susceptible genotype — where the FF becomes the dominant genotype,” she said. “I still model a significant decline in the population.”
www.nature.com
