Urinary cortisol, urea nitrogen excretion, and winter survival in mule deer fawns Academic Article uri icon

abstract

  • Physiological indices are commonly used to assess the condition of wildlife populations. The underlying assumption when using such indices is that they are associated with survival rates and/or reproductive success. However, such an association has never been demonstrated conclusively in wildlife populations. From 7 December 1987 to 15 April 1988 we monitored survival of 101 wild mule deer (Odocoileus hemionus) fawns in 2 fenced pastures, and determined levels of cortisol: creatinine and urea nitrogen: creatinine ratios in urine of 14 tame yearling mule deer using the same ranges. The 2 pastures were stocked with deer in November-December 1987 at high ( $0.66\text{km}^{2}$ ; 41 adults, 50 fawns, 7 tame yearlings; 148 deer/km2) and low (1.69 km2; 29 adults, 51 fawns, 7 tame yearlings; 51 deer/km2) density. Mean weekly cortisol: creatinine and urea nitrogen: creatinine ratios were associated with weekly fawn survival only in the high density pasture. Cortisol: creatinine also accounted for the effects of initial population density. Urinary cortisol: creatinine has the best potential as an indicator of condition in mule deer, but more research is needed before it can be considered a reliable tool for assessing population condition.

publication date

  • October 1, 1992