EVALUATING THE EFFECTS OF FORAGE AVAILABILITY AND LANDSCAPE COMPOSIITON ON WHTE-TAILED DEER MORPHOMETRICS ACROSS THE EASTERN U.S.

White-tailed deer (Odocoileus virginianus) management often focuses on improving nutrition to increase deer morphometrics, and many landowners use harvest data to track management progress. Better understanding the relationship among deer morphology, nutrition, landscape characteristics, and climate should inform deer management throughout much of the eastern US. I collected deer forage data in 2021–2023 from 43 sites in 25 states across the eastern US and worked with cooperating landowners and managers to collect harvest data from 35 of those sites. Adult female body mass explained 64% of the variation in mature male antler size on sites across the eastern US, and a 4.4-cm increase in male antler size was predicted for every 1-kg increase in female body mass. I detected a similar relationship from harvest data collected in Mississippi, which confirmed this relationship occurs at multiple spatial scales, and managers can use female body mass to track changes in herd health towards their objectives. Among the 87 species/genera I collected as deer forage, forbs contained the greatest average nutritional content, followed by semiwoody and woody plants. Crude protein and phosphorus concentrations correlated within an individual plant, but the number of plants meeting lactation-level phosphorus requirements was limited, which indicates phosphorus likely is the most limiting nutrient for deer across the eastern US. Site-specific forage availability across most sites was far less than forage availability reported in studies that implemented experimental treatments to improve forage availability. Climate and landscape composition had the strongest influence on male and female morphology across the eastern US. Females were 1.4 kg heavier and male antler size was 4.9 cm greater with every 1˚C decrease in average annual temperature. Females were 1.6 kg heavier and male antler size was 7.1 cm greater with every 10% increase in landscape crop coverage. Site-specific forage availability influenced female body and male antler size after controlling for landscape effects. Specifically, female mass increased by 0.15 kg and male antler size increased by 0.7 cm for every 1 deer day/ha increase in NCC with a phosphorus constraint. Managers interested in increasing deer morphology should consider increasing forage availability within the context of their climate and landscape to help develop realistic management expectations.