Reproduction and Productivity of Moose in Northwestern Ontario

Abstract

A study of reproduction and productivity of moose (Alces alces) in the Red Lake Road area of northwestern Ontario was based on a macroscopic and, when necessary, a microscopic examination of 210 pairs of ovaries and an analysis of the ages of 1,177 animals killed by hunters in early October, 1957-61. Thirty-five percent of the yearlings and 86 percent of the adults had primary corpora lutea within their ovaries. The ovulation rate, calculated by counting the number of primary corpora lutea, was 127 per 100 adult cows and 37 per 100 yearling cows. An average of at least 33 percent of the moose whose ovaries were examined had experienced an early September estrous cycle which did not result in fertilization. There is a linear relationship between the number of pigmented scars of corpora lutea in a pair of ovaries and the age of a moose. Pregnancy rates determined by microscopic identification of 6-month-old pigmented scars of corpora lutea of pregnancy were 17 calves per 100 yearlings and 113 calves per 100 older cows. The fertilization rate for adults was 89 percent and for yearlings 45 percent. Net productivity was 24 percent. Gross productivity and rate of increase were 25 percent and 34 percent, respectively. A yearling vulnerability factor ranging from 1.4 to 1.8 was determined for the 5 years of data. Comparisons of the Ontario data, obtained by ovarian analysis, with data from other areas reveal many similarities and show that the herd was as productive as any reported in North America. This report on moose reproduction and productivity is based on a macroscopic and, when necessary, a microscopic examination of 210 pairs of ovaries and on an analysis of the ages of 1,177 moose killed by hunters during the hunting seasons from 1957 to 1961, inclusive. Recent studies in Newfoundland (Pimlott 1959) and British Columbia (Edwards and Ritcey 1958), based on macroscopic examinations of ovaries or uteri collected during the winter months, have greatly increased the available knowledge on moose reproduction. These studies also have shown there is considerable variation in the reproductive rates of different herds and demonstrated a need for studies within specific herds. Although the moose season extended from October 1 to December 24 during the years that data were collected for this study, most of the hunting pressure and harvesting occurred during the first 2 weeks. Since this coincides with the end of the main rutting period, it is too early in the gestation period to determine pregnancy by gross examination of the uteri for embryos. However, it is during this period that large numbers of reproductive tracts and lower jaws of moose can be collected with the least expenditure of time and money. For this reason an ovarian examination was made to determine reproductive characteristics of the herd. Virtually all of the specimens were obtained from a study area of approximately 3,500 square miles located in the Sioux Lookout and Kenora Forest districts of northwestern Ontario. The boundaries are 93'45' W on the west, 92o30' W on the east, 51' N on the north, and 50'10' N on the south. The study area lies within the Boreal Forest Region (Rowe 1959) and is composed of three different sections: onehalf in the Lower English River section, one-third in the Upper English River section, and one-sixth in the Northern Conifer-