Moose population decimated by brain worm

Ken Johnston

While the number of deer in the area has continued to grow in the past few years, that has had a directly negative impact on the moose population.
Scott McAughey, Ministry of Natural Resources Biologist, said that recent aerial surveys of the moose numbers on the Aulneau Peninsula (Wildlife Management Unit 7A) and the region around Lake of the Woods (Wildlife Management Unit 7B) have shown a marked decline.
In the 1990s the Aulneau has, “Historically had the highest moose densities in the province,” said McAughey. That population peaked at about 1,000 animals in the mid 1990s. In 2000 when MNR did a count the number had dropped to about 600 and during the count this past January the figure is down to about 300. While that is a significant drop, McAughey said that in the 1970s and 80s there were fewer than 200 moose there.
In 7B the number of moose in 2000 was about 1,700. That dropped by more than 35% to about 1,100 this January.
The main reason attributed to the decline in the Moose population is not hunting but in fact a parasite known as Brain Worm. The parasite which attacks deer without killing them does not have the same effect on Moose.
Moose when infected with Brain Worm become tame and eventually die. McAughey said that being that moose are not native species to North America (the were brought in from Europe) they are not able to physically cope with the parasite. While others like the native elk or caribou seem to be able to deal with it better.
With the low levels of snowfall in the last five or six winters the deer have managed to have extremely high survival rates. Once the snow depths reach about 50 centimeters or more then deer have more difficulty moving around or escaping predators. They also have a harder time finding food and many end up starving to death.
McAughey said that two consecutive bad winters are needed to have a significant impact on the deer populations.
With such high numbers of deer, 4-5 of them per square kilometer in this area, there is a greater chance of moose getting the parasite. Brain Worm larvae are passed out through deer fecal matter. It is then consumed by land snails. The parasite then changes the behavioral patterns of the snails. They tend to climb up to the tips of leaves on trees and are then inadvertently eaten by moose.
The more deer the more parasites out there.
McAughey said emphatically, “There is no evidence to suggest that hunting had a (detrimental) impact on the (moose) population.”
However, with the decline in the moose numbers MNR officials are recommending fewer tags be issued to resident hunters this year. Last year there were 100 bull tags issued in 7A. McAughey said that the approximate number being recommended for this year is 75. In 7B there were 250 bull tags issues last year, this year about 230 is being recommended. About 10 fewer cow tags are being recommended for 7B as well.
While this might be disappointing to moose hunters, the flip side might excite some deer hunters. MNR is looking at issuing an additional tag to resident hunters. “They may be able to take two deer instead of one,” said McAughey. The details of that proposal have yet to be finalized, but McAughey said that hunters would likely have to take one male and one female and not two of the same sex.
However, that increased harvest would in McAughey’s view not have the desired impact to reduce the deer population to the point of saving the moose population.
“The only thing that will really make a significant difference is climate,” concluded McAughey.