The letter in the Nov. 10 issue regarding deer management appears to be based on very limited information and assumptions. The statement that the D.N.R. assumes deer and moose cannot co-exist is bogus. As D.N.R. Area Wildlife Manager at Grand Marais from 1969- 2000, we knew they can co-exist here, but not at high population levels of both.
The writer mentions the population situation back in the mid 1990s. One needs to step back farther in time to see the population changes of both species over time. The moose season was closed after 1922 because of a low population, primarily due to very liberal harvest regulations.
The extensive logging and fires in the early part of the 20th century created very good habitat for both species. Deer numbers mushroomed, moose numbers remained quite low and there were reports of what came to be called “moose sickness”.
This situation persisted until the mid- 1960s when a series of 6 out of 7 winters that were exceptionally long and severe decimated the deer population. During those years the moose population increased markedly and a moose season was held in 1971, the same year that the deer season was closed due to a very low deer population. The moose herd continued to increase and more open moose hunting zones were added.
The deer herd very gradually increased, but every few years severe winters knocked the population back. Even after it increased enough that a few antlerless permits were issued, severe winters still were frequent enough to reduce the deer population to where antlerless permits were not issued for a few years again. The frequency of severe winters decreased in the late 1990s, which resulted in a large increase in deer numbers.
Winter severity controls the deer population here, not hunting, wolves or car-kills. When walking through deer wintering areas after severe winters I always found many dead deer lying curled up in their beds, usually untouched by scavengers. Mild winters result in deer population increases.
It was in the late 1960s that Canadian wildlife biologist Roy Anderson found that the causative agent for “moose sickness” was the parasite that came to be known as the brainworm. Once biologists knew what to look for, it was found that a number of moose declines were the result of many moose becoming infected with this parasite. It is a common and harmless parasite in white-tailed deer, but causes a debilitating and often fatal neurologic disease in moose.
First-stage larvae of the parasite are passed on the surface coating of deer feces. Various species of land snails and slugs become infected as they come into contact with the larvae, which then advance to second and then third stage larvae in the gastropod.
When the infected gastropods are ingested while the deer or moose is feeding on vegetation the larvae burrow through the stomach linings, find nerve tissue and follow it up and forward in the animal to reach the brain.
Common signs of brainworm infection in moose prior to death (also caribou, elk, mule deer, pronghorn antelope, bighorn sheep, llamas, and domestic sheep and goats) include walking in circles, stumbling, lameness, loss of fear of humans, paralysis, etc.
The more deer, the more brainworm infected moose die.
In 1991, the moose season was closed in NE Minnesota due to numerous reports of dead moose.
The cause of death–massive infestation of winter ticks. Juveniles of this species of tick climb onto moose in the fall of the year, but do not become noticeable until late winter when the fully engorged females (about 1/2 inch diameter) cause enough irritation that the moose rub against trees and brake off their insulating hair.
The result is that moose must utilize their fat reserves to make up for the increased heat loss from lack of hair. In severe cases the moose is nearly devoid of hair and are often referred to a “ghost moose” because they are so light colored. In addition to the heat loss, moose can become anemic from the loss of blood to the ticks.
Estimates of the number of ticks on many of the dead moose are often around 100,000. That is a lot of ticks and amounts to a lot of blood. Whether the actual cause of death is from running out of energy to stay warm or from extreme anemia is immaterial — they died.
Winter tick abundance is also controlled by winter severity. The ticks fall off moose in April. If they land on snow, they die in a week. If they land on snowless ground, they lay eggs and produce the next generation of ticks.
Winter severity is critical. Long severe winters keep deer numbers low and winter tick reproduction low. Short mild winters result in deer increases, an increase in brainworm infected moose deaths, and tremendous numbers of the next generation of winter ticks.
Brainworm and winter ticks undoubtedly played major rolls in our moose decline. At this low level, it is likely that wolf predation can now also play a roll.
Regarding his question of where deer would come from if they are destroyed here. Answer: the same place they came from when they came into NE Minnesota when logging began in the early 20th century– nearby areas. They were not here before. Historically caribou was the most common big game species here, moose was second most common.
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