All wildlife biologists learn in their first ecology class about a relationship called Bergmann’s Rule: within a species, or group of similar species, body size increases with latitude from south to north. It’s assumed this adaptation is related to thermoregulation in extremely cold and warm environments. The bigger your body is in a cold environment, the easier it is to conserve body heat (as the body gets larger the relative surface area of the body decreases, so it takes less energy per pound of weight to keep an animal warm). The opposite is true for critters in warmer climates – smaller is better, because it’s easier to keep cool with relatively more surface area exposed for evaporative cooling. When you think of white-tailed deer the theory seems to hold. Deer body size in the North is generally larger than in the South; the extremes are exemplified by Florida Key Deer where a mature buck may weigh 60 pounds and a similar buck in Minnesota may weigh 300 pounds.
But what about antlers? Does the same trend hold?
The Mississippi State University Deer Lab explored this question by requesting antler size data from states and provinces throughout the whitetail’s range. We would have loved to use Boone & Crockett Score, but very few state agencies routinely collect those data due to time constraints. What we chose to use was antler beam diameter for yearling bucks. Beam diameter has long been collected by biologists as a metric of buck quality and is generally correlated with overall antler size. Our request to state agencies resulted in 74 data points that we plotted on a map of North America to examine the relationship between latitude and antler size.