Bergmann’s Bucks

Mississippi deer now have plenty to eat, and they’re really packing on the pounds.

The maddest Robin Callender ever got at a deer-hunting trade show was when a hunter from Michigan approached his booth, which displayed bucks harvested at his commercial operation in Claiborne County, and proceeded to tell him there was no way Mississippi had whitetail bucks that big.

“I was never quite sure if the guy was calling me a liar or if he was just stupid, but let’s just say he was not pleased with my response,” said Callender, guide and owner of Cedar Ridge Guided Hunts near Port Gibson.

That was more than 20 years ago. Back then, Callender’s clients were already harvesting bucks weighing more than 200 pounds on a regular basis. Deer weighing over 200 pounds back then were a pretty rare occurrence.

These days, it is much more common to see bucks tipping the scales at over 200 pounds. In fact, I had one camp call me last season about a palmated buck that blew the scale off their records at 240 pounds.

Evidence continues to surface each year about the increasing deer weights of both bucks and does across the state. So what does this whitetail weight gain mean to land managers and hunters? Is Bergmann’s Rule still valid as a theory of animal weights relative to their home ranges across America?

Bergmann’s proposition

What is Bergmann’s Rule? Wikipedia has a good definition: “Bergmann’s Rule is an ecogeographic rule that correlates latitude with body mass in animals. Broadly, it asserts that within a species, the body mass increases with latitude and colder climate, or that within closely related species that differ only in relation to size that one would expect the larger species to be found at the higher latitude.”

Hence the relative size and weight differences of say the small Keys deer in Florida as compared to whitetails in Mississippi as measured against the brutes of the upper Midwest in Michigan, Minnesota and Wisconsin.

The German biologist Christian Bergmann came up with his theory in 1847, and it remains controversial in certain circles today. One, however, can hardly argue with what has always been openly recognized as a “north to south” difference in whitetails when it comes to overall weight and length.

Northern deer can measure 8 feet long. In Texas, they go 6 feet to less than 5 in southern Florida. Northern territory bucks can weigh 300 pounds live weight or more. The national average for white-tailed deer is 125-200 pounds, and the Florida Keys subspecies go about 50 pounds. This seems to substantiate Bergmann’s rule.

Weighty trends

When one examines the harvest data of deer taken on private DMAP clubs in the state, some interesting things begin to pop out. From hunting seasons 1991 through 2006 on age-class bucks from 6 months to 8.5 years of age, the data shows increases in the average weights of deer harvested in all but one age class. The average weight gains go from 6.8 pounds to over 23 pounds. Doe weight gains shown are much lower, but evident.

Clearly, there are demonstrated average weight gains by our bucks over this 15-year period. Whether this data would hold up under strict statistical scrutiny, only an expert with a good statistical analysis software package could substantiate. Even so, our bucks have been putting on a few pounds, and this is likely a positive indicator of herd health, quality habitat resources and quality deer management practices on private DMAP lands.

“I don’t think there is any doubt that the bucks on our land in Hinds County have been gaining weight over the years,” said Chris Clifton of Madison. “The 140-class buck I took last year weighed over 200 pounds. We think our management plans and quality food plots are starting to make a big difference.”

The dirt on big bucks

Another scientific idea has been propagated by Mississippi whitetail biologists and university wildlife professors for some time. This concept makes the connection between the various soil types found across the state and the number of acres it takes to support one deer on the habitats produced by those different soils.

The lower the number of acres per deer would seem to indicate a higher quality habitat that is producing browse with a greater nutritional value. For example, on batture soil, it takes only 133 acres to support one buck, as compared to sandy Coastal Flatwoods soil that takes 941 acres to support one buck.

Obviously, the better the soil, the better the habitat Mother Nature can produce. Likewise, the assumption is the better the deer that can be sustained on these better habitats. This is why bucks tend to be bigger along the lands associated with the Mississippi River, but smaller in the coastal counties known for sandy soils, pine forests and substantially less available quality browse.

Deer-management equation

So we are back to asking again why our bucks are gaining weight on average all across the state, because not every deer club resides on the best soils. It is likely because of the pro-active deer management practices so many clubs have adopted over the past decade, especially in terms of providing viable supplemental food plots and other habitat enhancements.

“Heck, 15 years ago we never planted a food plot. We just assumed our deer in Madison County were getting plenty of food from nature,” said Gerald Moore. “Then we got educated. We attended wildlife seminars, read more and watched deer-management programs on television. Young hunters came to camp with lots of new ideas, and subsequently we got into the deer food-farming business. It has made a big difference in our buck weights and their racks.”

Could it be that private landowners and clubs are contributing to making the difference in these weight gains? Is it plausible that this has been accomplished by adopting the practices of planting spring and fall food plots, adding high quality forage for deer to use all year long? Have QDM practices played a role in this?

It seems logical.

All of these efforts to improve whitetail habitat including creating new wildlife food resources and bolstering existing browse have contributed to providing additional high-quality supplemental foods for deer. It may be difficult to prove, but this could well be part of the reason Mississippi deer seem to be experiencing a gradual weight gain.

For many deer hunters, this translates into healthier bucks with bigger racks and weights tipping over 200 pounds.

Bergmann’s Rule may well be right that northern whitetails are bigger than their southern cousins down here in Mississippi. However, our deer are gaining on them both in terms of weight on the hoof as well as antler rack inches mounted on the wall. This has been the result of a lot of hard work in adapting the principles of quality deer management.