by: Tony Duke
WINTER 1984
Three hundred dollars was not an unusual price for a Nova Scotian trapper to get for a bobcat pelt in the late 1970's. Quickly word got around that long haired fur (foxes, raccoons, and bobcats), was valuable. So in two years the number of trapper's licenses the Department sold almost doubled. The trapper wanted most to catch a bobcat, and, luckily enough, the bobcat population was high because their maid food item, the rabbit, was also at the peak of its cycle.
Than came the crash. By 1981 the rabbit population had fallen. By 1982-83 the bobcats fell and by 1983-84 trapping license sales were back to early 1970 levels. The pelt price had fallen too but that probably reflected the whims of fashion more than anything else.
What biologists and those interested in furbearers see here is the natural predator-prey crash at the end of a population cycle. It is an extremely complicated process which has fascinated biologists for decades. Only in the lat year or two have they been able to pin-point any causes. First the number of prey animals declines probably as a result of a lack of food, and actual starvation. So then the predators are out of food and their numbers decline too.
Since it is impossible to count all the rabbits and bobcats in the province we have to use harvest statistics to give us an indication of what the populations are doing. We believe that the number of rabbits and bobcats taken by hunters and trappers generally reflects the total population of animals (i.e., high population = high harvest, low population = low harvest). The harvest figures for the last six years are pictured in the graphs below for the three regions of the province. You can see how both populations reach a peak, crash and begin to rise again. You should also note that it is the prey that brings the predator population down, not the predator keeping the prey down as you might believe. The predator population crashes one to three years after the prey.
Trappers have been helping with our study of bobcats by turning in the carcasses of animals they catch. by examining these, wildlife biologists find out what the animals were eating and how much fat the animal had to provide energy through the winter. From the female's reproductive tracts they found out pregnancy rates and litter sizes. From the teeth, they determined the animal's age. All these data than become a sample for the whole population.
From the work a complex picture emerged. The three regions of the province were difficult and each age class was different. But generally the biological theory proved out.
When food was abundant female bobcats survived the winter in good physical shape and were able to conceive and raise large litters in the spring. Lots of food for the kittens meant more of the females bred in their first year. When food became scarce the litters were smaller, fewer kittens survived, there were more barren females and very few yearling females had kittens.
In 1980 the yearling pregnancy rate was 68%. During the 1982 low in the bobcat cycle it fell to 39%. But more food for surviving bobcats allowed 68% of yearlings to conceive and have kittens in 1983, indicating the upturn in the cycle again. For the same three years litter sizes of yearlings averaged 2.4, 2.2 and 2.8 kittens showing a bottoming out and the beginning of an increase.
If the percentage of young animals in the population is high it means the population is growing. Thirty nine percent of the animals trappers took in 1983-84 were kittens and only 8% were adults 3 = years old and older. both of these numbers could be key indicators to productivity and could be useful for determining bobcat well-being in the future.
The weight of the fat on the carcass and in the body cavity was used as an index to the condition of each cat. Although cats with no fat were found throughout the province, preliminary results suggested that Cape Breton cats had a higher index (were in better condition) than did mainland cats. Older cats were in better condition that younger ones and males were in better condition than females. Cats in general seem to be putting on fat well into January.
More than two-thirds of the cat stomachs contained food items. These were identified and weighed. to complete the year-round food habits picture, we also collected scats throughout the province during the spring and summer.
Snowshoe hare is the most important food item. It occurred in three-quarters of the mainland cats and two-thirds of the Cape Breton Island cats. Deer occurred in one out of four stomachs in 1980-81 but fell to one-tenth the following year. Small mammals like voles and shrews are more prevalent in the diet of Cape Breton Island bobcats. Male cats consume deer more often than do females. birds, primarily ruffed grouse, and other mammals like the red squirrels and porcupine, make up the remainder of the cat's diet in the province. there appears to be no major difference in food habits between fall-winter and spring-summer.
High prices and heavy trapping pressure at a time when bobcats were numerous brought in nearly two million dollars to Nova Scotia trappers between 1977 and 1982. With or without trapping the bobcat population would have collapsed and recovered naturally. The trappers asked for a reduced snaring season to assist the current recovery of the bobcat. So this renewable natural resource provided income and recreation instead of going to waste.