Smaller body sizes are more efficient at cooling during hot weather. In Missouri, deer are heavier and sport better racks in the northern half of the state. Latitude may play a role, but the range quality likely plays a greater role. Superior soils and abundant agriculture in northern Missouri offer better nutrition. Deer lose weight during winter and then undergo a phase of rapid growth during spring.
Bucks often lose weight during the breeding season, but regain it during spring.
Females with fawns begin to lose weight in January and do not regain it until late summer when fawns are weaned. Some studies suggest deer undergo stress periods and lose weight during hot dry periods. Most deer activity takes place around dusk and dawn with brief periods of activity during midday. These patterns vary with the time of year and the weather. Recent studies suggest that deer are most active at low humidities and show increased movement during overcast periods.