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Tuesday, January 30 • 9:00am - 9:20am
UNGULATES: Pregnancy Rates and Body Condition of White-tailed Deer in Wisconsin

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AUTHORS. Amanda McGraw, Joe Dittrich, Dan Storm - Wisconsin Department of Natural Resources

ABSTRACT. Habitat productivity, climate, and interspecific competition influence reproduction and non-harvest survival through their effects on energy balance.  Energy balance is reflected in body condition, including fat reserves.  As such, we developed body condition indices based on fat measurements from multiple fat depot sites on about 1,600 deer during springs of 2014-2017.  Additionally, we assessed pregnancy and litter size for about 950 female deer.  Using remotely-sensed landcover and weather data, we investigated the interacting influence of habitat and weather on deer body condition.  We found strong regional variation in body condition; deer in farmland regions in eastern, western, and central Wisconsin were in better condition following winter than deer in the forested regions in central and northern Wisconsin.  Body condition also varied strongly by year and winter severity within regions.  Juvenile deer (deer experiencing their first winter) had consistently lower body condition than adult deer.  Differences in body condition between juvenile and adult deer were largest during the severe 2013-2014 winter for deer in northern and central forests.  Pregnancy rates of adult deer were consistently about 90%, statewide.  Lowest juvenile pregnancy rates were observed in northern forests, averaging 4% over 4 years.  Notably, no juvenile deer in northern and central forested regions of the state were pregnant in spring 2015.  This could reflect the impact the severe winter of 2013-2014 had on neonate birth weights, subsequently leading to poor body condition in the fall and precluding fawns from being bred.  Comparatively, juvenile deer in western and eastern farmland regions did not experience a decline in pregnancy rates in spring 2015, and have an average pregnancy rate of 13% and 22%, respectively.  Our results clarify how habitat and weather influence spatial variation in population performance in white-tailed deer.

Tuesday January 30, 2018 9:00am - 9:20am CST