Reproduction of Shiras Moose in Montana

Abstract

Reproduction and productivity of Shiras moose (Alces alces shirasi), based on macroscopic examination of 424 female reproductive tracts plus analysis of sex and age of 1,581 animals harvested in Montana in 1963 and 1965-1971, are reported. Forty-three and 92 percent of yearling and adult cows collected after 1 October had ovulated, respectively. Ovulation rates were 48 and 115 per 100 yearling and adult cows, respectively. Pregnancy rates were 32 and 86 percent for the same respective age groups. Yearling and adult twinning rates were 0 and 16 percent, respectively, with 32 and 100 calves per 100 cows for the same respective age groups. Yearlings were no more, or less vulnerable to hunters than adults. Gross productivity, net productivity and rate of increase were 25, 20, and 34 percent, respectively. Comparison of our data with that from several other regions indicates that Shiras moose in Montana are equally as productive as any other North American moose herds studied. Differences between in utero and post partum productivity are discussed. J. WILDL. MANAGE. 37(4):535-544 Determination of ungulate reproductive performance by macroscopic examination of ovaries and/or uteri is a well-established technique. These methods have been applied to moose by Edwards and Ritcey (1958), Pimlott (1959), Peek (1962), Simkin (1965), Houston (1968), and Markgren (1969) among others. These studies have added greatly to our knowledge of moose reproduction, and at the same time indicated that wide variations exist in reproductive rates of moose from different areas. This study was prompted by the paucity of quantitative data on moose reproduction in Montana and because data of Peek (1962), Houston (1968), and Stevens (1970) suggested that perhaps Shiras moose populations had lower reproductive and/or calf survival rates than other moose subspecies. Houston (1968:70-71) further postulated that some genetic influence over twinning might occur in the Jackson Hole area of Wyoming. This study was initiated in 1965 to investigate the reproductive characteristics of Shiras moose in Montana in order to determine whether reproduction was actually below normal and, if so, to attempt to determine causes and appropriate remedies. Sex and age composition of harvested moose are also presented and discussed since they effect overall reproductive performance. This study could not have been carried out without the cooperation of successful hunters, and of the numerous persons who graciously allowed use of their facilities as collection stations. K. R. Greer and his staff at the Montana Fish and Game Department's Wildlife Laboratory assisted in preparing and handling collected materials. J. M. Peek, D. B. Houston, and R. L. Phillips critically reviewed the original manuscript and offered valuable suggestions for its improvement.