Effects of enhanced winter nutrition and climatic variation on population performance of a large herbivore
Population performance hinges on optimal allocation of available energy by individuals to competing life-history traits. Life-history strategies of long-lived, iteroparous mammals often involve prioritizing energy allocation to adult survival over any single reproductive event, therefore maximizing future reproductive potential. Therefore, a commonly observed energetic tradeoff in large mammals is between current and future reproduction rather than between reproduction and survival. Survival of adult female ungulates is generally high and stable, whereas recruitment of young is more variable. Nutritional condition and climate have the potential to influence demographic parameters that affect population growth. We focused on evaluating the effects of enhanced winter nutrition and environmental factors on survival of adult female and neonatal mule deer (Odocoileus hemionus) and associated effects on the population growth rate (λ). We modelled effects of individual and environmental covariates on survival of adult female mule deer from 2013 to 2018, and neonatal mule deer from 2014 to 2016. We observed a declines in adult survival in response increased snow depths which contributed to negative population growth rate in 2017. Enhanced winter nutrition of maternal females resulted a substantial increase in survival of neonates to weaning. The strong effect of enhanced winter nutrition on juvenile survival demonstrates the importance of forage quality available to adult females during mid-pregnancy.
demography, ecology, mule deer, nutrition, Odocoileus hemionus, population demographics
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