Assessment of Natal Mortality in Upper Michigan Deer

Abstract

This paper describes methods of assessing the annual magnitude of natal mortality in white-tailed deer (Odocoileus virginianus) due to inadequate maternal nutrition. Marked differences in fetal development during late gestation were indicated over an 8 yr period in Upper Michigan [USA]. Growth curves extrapolated to term yielded mean body weights varying from 3.24-2.27 kg. Based on their predicted size, it was judged that 10-70%, respectively, of the fawns died at birth. The proportion of pregnant does considered to be in good physical condition at time of death ranged from 0.85-0.13, following winters in which the weather severity indices were 21-36, respectively. Annual data for the 3 parameters were significantly (P. < 0.01) correlated. There was a significant (P < 0.05) relationship between estimated natal losses and the fawn/doe kill ratio for the ensuing harvests. Application of study findings are discussed.