Chronic wasting disease continues its death march across Alberta, west from Saskatchewan, from whence it came to who knows where, eventually.
CWD is an always-fatal disease of deer, elk and moose caused by virtually indestructible particles of abnormally folded protein called prions. It is similar to mad cow (bovine spongiform encephalopathy) or Creutzfeldt Jakob disease, but has not yet jumped to humans as mad cow has.
Alberta Fish and Game Association president Wayne Lowry commented recently on the results of the mandatory testing program of deer, moose and elk heads taken by hunters in Alberta’s infected areas in 2014: “CWD continues to be a major concern of AFGA as it increases both in numbers and geographic scope.
“There have been positives found in Wildlife Management Units 144 and 142 for the first time as this disease spreads further west from CFB Suffield towards the Brooks area,” Lowery said. “In Alberta, known CWD cases now number 297 and stretch from Lloydminster in the north to very close to the U.S. border in the south, and have now stretched west past Hwy 36 around the Hanna area in WMU 160. Debate continues as to how this is going to be managed, and AFGA will continue to press for more than just the current surveillance program.”
Dr. Margo Pybus, provincial wildlife disease specialist, reports on the head-testing program: “We have completed all of the 2014 fall CWD surveillance samples received to date. In 2014, we tested 4,163 heads and detected 86 cases of CWD (2.1 per cent). CWD was confirmed in 74 mule deer (59 males, 15 females; 72 adults, two yearlings) and 12 white-tails (all males; 10 adults, two yearlings).”
The current annual report eerily echoes every one since they started in 2005: that mule deer are much more susceptible to CWD than white-tails, and mule deer bucks are more at risk than does.
I loved to hunt mule deer, got know them fairly well and suspected that their social habits and … ahem … sexual behaviours might be the cause of their higher risk of CWD infection than white tailed deer.
In the absence of answers anywhere else, I finally went to the top, to Valerius Geist, professor emeritus of environmental design at the University of Calgary, now retired to Vancouver Island. Geist is one of the world’s foremost animal behaviourists and has become an authority on CWD. Among his many books are Mule Deer Country and Whitetail Tracks.
“CWD is transmitted via body fluids,” Geist told me. Mule deer form home-range groups of related females, he explained, which lick and groom each other, as well as lick each other’s tarsal glands on the lower rear legs — the “passport” of each deer. These glands are saturated with urine. Therefore, within the home-range group of mule deer females, each member comes in contact with the saliva of others, as well as the urine in the tarsal gland. Consequently, CWD infections follow home-range groups.”
Geist told me that white-tailed deer are much less likely to form close-knit social groups and there is consequently less chance of passing body fluids between individuals. In fact, white-tailed does can be virtually territorial so that an infected doe passes CWD at best to her offspring.
Then we got to a mule deer buck behaviour I observed often when I was staking out herds of mule deer does during the rut, watching for a huge buck I always called “Horseshoes” suddenly to appear from somewhere and commence nose-goosing (or so I thought) this doe or that.
Val Geist gave the straight, if unsavoury story on what is really happening here.
“Comes the rutting season. Mule deer bucks court does and this includes — repeatedly — taking the urine of each doe into their mouth to test it via the Jacobson’s organ in the front of the upper palate to determine if the doe is ready for breeding. That’s the ‘flehmen’ response, or ‘lip curl behaviour.’ Mule deer bucks move between home-range groups of does, before they settle down to stay more or less with one group. As you can see, by going between groups, bucks are more likely to take into their mouth the urine of infected does, while mule deer does are restricted pretty well to the group they live with.”
So there we have, just as I suspected, the reasons why mule deer, particularly bucks, are highly susceptible to ingesting the CWD-causing prions. Unfortunately this information is unlikely to be of much use in the coming big battle to combat CWD. There will be no “Practice Safe Sex” program for mule deer, and its social and sexual habits can be added to other evolutionary behaviours that Geist believes doom the species to eventual certain extinction.
Bob Scammell is an award-winning columnist who lives in Red Deer. He can be reached at firstname.lastname@example.org.