Relationship between winter severity and survival of mule deer fawns in the Peace Region of British Columbia

Abstract

This extension note summarizes results of an ongoing study to measure the survival of mule deer (

Odocoileus hemionus) fawns through their first winter in the Peace Region of British Columbia. Each spring since 1991, mule deer were counted and classified by sex and age by driving along roads that go through areas known for providing good winter range. Seven transects were driven for a total distance of 205.3 km. The number of fawns observed is expressed as a ratio of fawns per 100 does. Average monthly air temperature and total monthly snowfall data from November to the following April from 1991 through 2008 were obtained from Environment Canada’s website. A winter severity index (WSI) integrating temperature and snowfall data was calculated and correlated to the observed fawn-to-doe ratio. A statistically significant relationship between this ratio and the WSI was obtained through  regression analysis. Resulting data confirms previous research that showed survival of fawns through their first winter is higher in milder winters. For the same time period, we also compared WSI values for the Peace Region with those from three other areas in British Columbia. Results indicate that, on average, the Peace Region experienced harsher winter conditions than the other regions. The variation of the WSI was also much greater in the Peace Region. These results have implications for mule deer management in this region.