What's Behind the Declining Caribou Population?
October 26, 2017
Caribou are making news on two different continents. In Canada, Quebec has announced that all sport hunting for caribou will cease in February 2018. In Norway, two reindeer were found with CWD, the first ever found in all of Europe. Actually, reindeer are simply a domesticated version of caribou. Although domesticated, there are some wild reindeer in Norway where an estimated 30,000 exist in 23 different herds.
Norway hunters harvest between 4,000 and 5,000 reindeer each year, but the accidental discovery of CWD is about to change everything. In March 2016, a wildlife biologist found a sick reindeer in a mountainous area. It turned out to be CWD-positive, and that led to extensive testing that resulted in two more CWD-positive reindeer from the same area. The herd in that area contains 2,000 animals and a panel of experts, after a lengthy study, decided to take a drastic step and attempt to harvest them all to eliminate CWD in the region.
Hunters will begin the attempted extermination this August. They can only eat the meat if testing shows their harvest is CWD-negative. Once the season is over, sharpshooters will go in and attempt total removal of all remaining animals in that region. In the meantime, known movement corridors for that herd will be monitored, and any animals seen leaving the 772 square-mile area will be killed.
The interesting speculation is how did Norway get CWD? One suggestion is that it came from whitetails in Finland. The Finland deer originated from America in 1934, and it is possible that CWD was brought in. However, since that introduction was only four deer, it is very doubtful that such a small number of deer was the source of Norway's CWD.
Will it be possible to kill the entire herd in this 772 square-mile area? Attempts to kill deer in American CWD hot zones have largely failed. The one exception was a local outbreak in New York, where many deer were subsequently killed and no further CWD was found. It is unknown whether this attempt at total removal of a reindeer herd will be successful, but reindeer herds migrate in relatively predictable travel corridors, making total elimination possible. Total elimination may not occur, but most will be harvested.
Let's say that they do eliminate all reindeer. Then what? We know that the infective agents, prions, are found in urine and feces, but what is not known is how long they can remain viable in the soil. Based on preliminary observations, it would not be surprising if such viability is possible for decades. If any of the harvested reindeer have CWD, then they've left infective prions in feces and urine in the soil. The persistence of prions may mean that when reindeer move back into the area, they will again pick up CWD. Then there is the fact that plants pick up the prions and can be eaten by reindeer later. All of these unanswered questions make this attempted herd elimination interesting.
Now, let's move on to the Canadian caribou situation. It really should not come as a surprise that Quebec is stopping all sport hunting for caribou. The two major herds, Leaf River and George River, have plummeted in recent years. The George River Herd was around 800,000 in 1985, while the Leaf River Herd fluctuated, but peaked at 640,000 in 2001. Today the George River Herd is thought to be around 5,000 animals, while the Leaf River Herd is down to 200,000.
But why the drastic decline? Quebec biologists recently published the best summary I could find on this situation (see "Biological Status Report of Migratory Caribou, Leaf River Herd"). It summarizes all caribou data from as far back as 1975, and also presents the results of all research presently being done. That research examines every aspect of caribou ecology, from reproduction to migration routes, population size, parasites, predation, hunting, climatic change, habitat, etc. If you are looking for one reason for the caribou declines, forget it. This situation is very complex.
Relative to recreational hunting, one piece of data was interesting. Hunters are interested in large bulls. The proportion of large bulls in the Leaf River Herd was 18 percent in 1995, 20 percent in 2000, 12 percent in 2005, four percent in 2010, and four percent in 2015. In 2015, the herd composition was 62 percent females, 20 percent calves, eight percent small bulls, six percent medium bulls, and four percent large bulls. Now you know why recent TV shows done in Quebec rarely show large bulls being taken. They aren't there.
Besnoitia tarandi is a protozoan parasite that causes cysts in the skin and infection. Data presented showed it in 30 percent of caribou in 2007, and 80 percent in 2011. The vector for this protozoan is most likely biting insects, and with global warming, the season for these insects is longer, thus enhancing the disease. One might surmise that this is a cause for caribou decline. However, since 2011, prevalence rates for this protozoan have dropped significantly, and there is no speculation as to why.
The report also considers wolf predation, habitat loss, and impacts on migration caused by new and large hydroelectric projects, hunting, access to areas via snowmobiles and four-wheelers, mining exploration, and natural fluctuations in populations. Climate change may be the biggest reason for declines, as it affects the vegetation. For example, there is now increased shrub cover on summer range. What does this do to caribou? There may be less lichens with increased temperature. What effect does this have? There is a change in winter rains and snow. What effect does this have on caribou?
Biologists in Quebec keep digging for answers. But research takes money, and the loss of hunting is having a huge impact on rural economies, as well as funds for research. Will we see the return of caribou hunting in Quebec in the near future? My guessC is that we will not. In fact, it may be decades before you can hunt Quebec caribou. These declines have little to do with recreational hunting, because biologically insignificant numbers are taken by hunters. Even so, perception is reality, and this left the government with little recourse. Some will disagree, of course, and will cry for more and better data to defend the closure. That's a Catch 22, because to continue recreational hunting when large bull numbers and overall populations were in decline didn't seem wise. However, total closure means far less money for much-needed research.
One cannot overestimate the economic impact the loss of recreational hunting will have on the small, rural villages in northern Quebec. There are no easy answers here, and for years to come the caribou in Quebec and reindeer in Norway will continue to be in the news.
If you have questions about topics covered in this column or on any wildlife-management issues or wildlife species, contact Dr. Dave at firstname.lastname@example.org