It’s deer season and my cousin Scott was lamenting that, contrary to the State’s motto, everything isn’t always bigger in Texas. His lament was that Nebraska’s white tail deer were larger than those he was hunting in Texas. He is correct. Nebraska bucks can be 50 to 100 pounds heaver than those from Texas.

The difference is due to latitude and average temperatures. Back around 1847, the German biologist Carl Bergmann noticed a trend in warm-blooded animals’ bodies as he made his way from southern Europe northward. He first noticed it in geese and then, after some investigation, saw the same trend in a number of mammals.

We now call it Bergmann’s Rule. It basically states that animals living in colder environments tend to be larger than their warm weather cousins. Bergmann explained that this is because of heat retention. Warm-blooded animals (birds and mammals) generate internal heat. That heat escapes the body through the skin. Thus, the body size of the animal in relation to the amount of skin controls heat loss. Larger animals tend to be able to endure colder weather better than smaller ones because they have a larger body size-to-skin ratio.

Next comes American Joseph Allen with another rule: “Allen’s Rule”. He noticed that while the bodies of the animals became more robust as you moved north…their extremities got smaller! Shorter wings, shorter legs, shorter ears, shorter tails, etc. Why? Same reason. A lot of heat is lost through the extremities… your hands and feet while shoveling snow, are an example. Smaller extremities equate to better heat retention.

One example of Bergmann’s Rule comes from penguins. The Emperor penguin is the largest of the penguins, and it lives in the coldest portion of Antarctica. It is twice the size of the Galapagos Penguins that live on the Equator.

A second example of Bergmann’s Rule, as well as Allen’s rule, is from right here in Nebraska “Archie”! Archie is the Columbian mammoth skeleton that greets you in Elephant Hall at the University of Nebraska State Museum. Found just north of Curtis in Lincoln County in 1922, Archie is 15.5 feet in height. Mammoths lived during the Ice Age. Their closest cousins alive today are African elephants that live in a warm climate. African elephants are smaller than the mammoths, and the largest ever seen was 13 feet tall.

The elephant and Archie also follow Allen’s rule about appendages. African elephants have huge ears to help dissipate heat. Their trunks, legs, and tails are longer in relation to their overall size than are that of mammoths, which had small ears (yes, there have been complete mammoth bodies found in the ice), stubby legs, and short trunks and tails.

So, no, Scott, because of Bergmann’s and Allen’s two rules of ecology, everything in Texas isn’t always bigger. Our fossils are bigger as well as our white tail deer! It may be hard for a Texan to accept that, but hey, rules are rules!