Fewer moose, more deer in east end of district

A combination of milder winters and increased access to browse has resulted in a sharp increase in the deer population in the Fort Frances area—to the detriment of moose.
These are some of the conclusions drawn by the Ministry of Natural Resources after completing its 2005 moose aerial inventory in Wildlife Management Units (WMU) 9A and 9B last week.
These two units are located east of Fort Frances almost to Atikokan and north to just below Highway 17. WMU 9A covers 4,500 square km while 9B covers 3,950 square km.
The surveys, which took place Jan. 15-23 for WMU 9A and Jan. 24-Feb. 11 for WMU 9B, involved over-flying specific plots within each unit and extrapolating on those observations to arrive at an estimate for the entire area.
Each plot measured 2.5 km by 10 km (25 sq. km), which amounted to 28 percent of 9A and 35 percent of 9B.
“We design these surveys to statistically estimate the population size and density in each unit,” explained MNR area biologist Darryl McLeod, who supervised the survey within WMU 9A.
McLeod said the goal of the surveys is to achieve a margin of error of no more than 20 percent. In this case, that margin actually was 19 percent in WMU 9A and 21 percent in WMU 9B.
The MNR conducts these surveys every winter, but only covers the same area every three years. The last survey in 9A and 9B was in 2002—there has been a definite change since then.
“There were more deer recorded in [WMU] 9A than in any previous survey,” noted McLeod.
McLeod reported 84 deer in that area while his colleague, John Vandenbroeck, spotted 127 deer in WMU 9B. McLeod estimated this translates into an increasing trend in 9A and a stable population in 9B.
But of more concern to the two biologists were the moose numbers. In both areas, the total number and population density were significantly down from those reported in the 2002 survey.
In fact, they represent a reversal in a trend that had been ongoing for more than 20 years.
“The [moose] population had been steadily increasing since 1983 when selective harvest rules were introduced,” remarked Vandenbroeck. “This is the first downturn since then.”
The downturn is fairly significant if the estimates are accurate. In 2002, for instance, there were 2,450 moose estimated to be in WMU 9A, which translated into a population density of 0.70 moose/sq. km.
The results of the 2005 survey indicate roughly only 1,550 moose and a population density of 0.45 moose/sq. km. McLeod said the target density range for that area is 0.50-0.70.
In WMU 9B, the numbers, density, and target density were lower, but that was expected because that unit isn’t capable of supporting as many animals.
What was of even more concern to the biologists was the composition of the observed population. In both areas, the percentage of calves had declined significantly while the number of cows without calves present was rising.
Neither biologist could offer an explanation for this trend, since the number of predators in the areas appear to be fairly constant.
There was some good news, however. Vandenbroeck said the ideal ratio of bulls to cows should be about 40/60 in order to maintain good breeding potential.
To a certain extent, this ratio can be adjusted through the allocation of moose tags during the annual hunt but, at the moment, the ratio looks good.
“With the cows-to-bulls ratio, we have good potential for future recruitment and recovery,” remarked Vandenbroeck.
But what caused the numbers to drop in the first place?
Both biologists feel the rising deer population is a significant factor because they are vectors for certain ailments that are dangerous to moose, although they were unwilling to say that was the sole cause.
“The deer population is definitely a factor in transmission of brain worm and winter ticks,” Vandenbroeck remarked.
Brain worm, or parelaphostrongylus tenuis, is a small parasitic worm that develops in the membranes of the brain and spinal chord of cervids, such as moose.
For some reason, deer seem to be less affected by the parasite, but are efficient carriers.
In moose, the presence of these parasites is characterized by weakness, head shaking, staggering, and lack of co-ordination. Once infected, moose in this condition are easy prey to wolves and bears if the disease does not kill them first.
Vandenbroeck and McLeod each reported one suspected case of brain worm disease in the areas they surveyed.
Winter ticks or moose ticks (dermacentor albipictus) also are carried by deer, which again seem to be less susceptible to their effects.
In moose, they are such an irritant that the animals often will rub themselves raw in an attempt to dislodge them. This can result in large areas of bare skin.
In harsh winter conditions, this exposed area can cause the animal to lose a great deal of body heat, resulting in severe hypothermia and death.
Once again, there was evidence of this problem in the survey. “Five of 21 calves in 9B had evidence of hair loss,” Vandenbroeck observed.
The MNR will establish the number of deer tags this year based on the results of this survey and harvest reports from hunters.

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