Bergmann's Rule

I glanced at the Wiki article because I remember reading in another article about 500lb WT that as latitude increases, so does body size in white tail deer.

I was talking to my "uncle" in GA this past week while we visited his cabin and lease near West Point, GA. He said Texas has much bigger deer than Georgia. I took him for his word but have been thinking about it since.

I know we have big deer, that's for certain. But how big?

In a rough guesstimation, I told him an average mature buck in Texas weighs around 180lb live weight--don't kill me, I don't know how accurate this is! He replied with "If a deer is 180lb here, it's like a 12-pt." Completely unscientific, but I think we can all understand the nonscientific backwoods comparison the two of us made: 180lb is a big deer in GA.

Mr. Paul Simone at Texana Springs Ranch in Hunt, TX once told me that the average WT doe in that area (his work with TPWD concentrated on Kerr WMA and of course management efforts on his current workplace of 2000 acres) weighed 80lb dressed out. We hunted with them in February of 2016 and all of our deer dressed out past 70lb with the biggest in the high 80s, if I remember correctly (all were doe except for 1 nubbin buck, which the ranch wanted dead anyway). I shot a 3.5/4.5 year old Madison County buck in 2010 that was around 100lb of meat and bone. I shot a Menard County 2.5/3.5 year old buck that was likely 60lb of meat and bone. That's how I got to the 180lb average weight for mature deer, considering that a) doe are smaller than bucks and b) I haven't shot a WT deer in the south or north of Texas, where I've heard (and witnessed) bigger deer and c) the bucks I've shot were not truly "mature."

Let me know your thoughts. I'm probably grossly ignorant on most of what I'm saying here (the paragraph above) and would like to know more. How closely does the white tail deer follow Bergmann's Rule, in your opinion, across both the USA and Texas?

think your fairly spot on. Never heard of the Bergmann Rule, but generaly farther north, bigger the deer. thinking further north cooler temps, it needs the extra body weight ta servive. Their is differance in average size here than cool thread

You can also see Bergmann's rule effects on antelope. If you travel up farther north you will definitely see the influence on whitetails.
Much larger body size and smaller ears. I've noticed the mule deer in Texas and south have much larger ears for heat dissipation. In agricultural areas up here and especially in Canada you will find bucks that push 300 lbs, mostly in agricultural areas of Canada and North Dakota. By ag I mean even just irrigated meadow hay .
The rule manifests itself even just up into Kansas and Nebraska.

Bergmann's Rule is a "rule" and not a "law." It only refers to generalities size clades in warm blooded animals and is not tied to latitude, but temperature/climate. Latitude only comes into play when there is a significant difference in temperature/climate. Warm-blooded animals in colder areas tend to be bulkier. Bergmann's Rule was formulated in the 1800s without consideration for contrary genetic factors, nutrition, etc.

So you are comparing Georgia and Texas. Georgia is within the same latitudes of Texas. So by latitude, the rule doesn't work at all. Texas extends farther north and south. So I would not expect to see a huge difference in size based on latitude. Georgia is slightly cooler than Texas, however, but this is not a latitude issue, but a weather pattern issue. Even so, it is not significantly different throughout much of the year.

Bergmann's doesn't even work in Texas for latitude or temperature where warmer south Texas deer are often larger than cooler central Texas deer.

Genetics and local nutrition play a part in it too.

A big south texas whitetail will weigh 240 or better on the hoof pre rut

I have buddies from Mississippi who shoot deer the same size as we do in south Texas, but they drive 40 miles and get into the delta and body weights increase 50 lbs. better groceries is the main factor

But as a whole I agree with Bergman’s rule.

In support of the 'better foods - more weight' side of the discussion; on a Llano county lease when we started taking more does off of the property as well as some of the old spikes and leaving deer to get older, our records showed:
When we started-
-average doe field dressed was 68 pounds
-average 8 point dressed was 74 pounds
-average age of a doe was 4.5 years of age (oldest was 9 or so)
-average age of an 8 pt was 2.5 (oldest was 3.5)
After 5 years of reducing the herd-
-average doe field dressed 52 lbs
-average 8 pt field dressed 105 lbs
-average age of a doe was 1.5
-average age of an 8pt was 4.5

I moved to Missouri after year 5 and took a whitetail doe there that field dressed 150 lbs. I would see several pictures at local check stations there of bucks weighing from 175-250 lbs live weight.

I hunted in Finland (about as far north as southern Alaska) and a white tail doe one of the guys took was estimated to weigh 100 kilos (approx 220 lbs) field dressed. I saw a 6 pt that looked to be about the size of a young steer.

Maybe those figures reversed?

In the same location and in the same state, nutrition and age play a huge part.

We have little deer here in VA. And we are definitely further north than Texas.

Doesn’t really apply. Our hill country does that are fully mature might average 80 lbs but a mesquite country south TX doe will easily push over 120.

North Tx panhandle deer get even bigger. I shot a doe last year the cleared 180.

Poplulation density and food quality play a role without a dought.

Doesn’t really apply. Our hill country does that are fully mature might average 80 lbs but a mesquite country south TX doe will easily push over 120.

North Tx panhandle deer get even bigger. I shot a doe last year the cleared 180.

Poplulation density and food quality play a role without a dought.

There is a reason that cattle drives that started in Texas ended in Montana. Food quality especially grasses are that much better to make that journey worth while. Then off to the Dakota's to auction.

How many cattle drives started in Texas and went all the way to Montana? Which trail did they use?

Negative

Cattle doing good or bad in Montana is an example of Bergman’s as to why certain variants of the two Aurochs sub sets do better in colder clients( the bigger species evolved in cold clients with regards to winter and the smaller evolved in warmers clients). Since Cattle are imported/cross breed etc to America they would be a poor example of an evolutionary change.

Really cattle are bad example of Bergman’s because of cross breeding of cattle over such a short time span, they don’t have a natural evolution for say anymore

Polar bears are the largest bears in the world, “Canadian” wolves are bigger then “Mexican” Wolves Etc are better examples.

Over all Bergman’s is just a small peice a whole lot of factors in animal size, and Bergman’s is often proven inaccurate, example would be African Elephants

Wonder how elephants in Africa compare in size to whooley mamoths that I would "think" lived in colder climates.

If you take supplemental feeding out of the question and agriculture how much do south texas bucks weigh? Most of the deer I see or hear about being well over 200 lbs are very well fed.

On a place we used to hunt in the hill country we observed long term dressed weights increase by about 20 lbs by bringing population numbers down.

Chital,

very good topic. There are some confounding variables. First, there are several subspecies of White-tailed deer. Before hunting was regulated with seasons and bag limits, deer numbers were dramatically reduced. Then during the Great Depression, they were hunted heavily for subsistence and really reduced in numbers, down into the 100's of 1,000's, and completely extirpated in many areas. After WW2, efforts were made around the country to reintroduce deer to areas where they had been wiped out. So, there are Texas subspecies in Georgia, as well as northern subspecies in Georgia. So, things are a mixed bag at this point. But to your point, body weights can vary significantly based on subspecies, food and water availability, hunting pressure and regulations affecting age, and other factors such losses to habitat destruction, degradation of water quality, and disease.

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It’s a general rule of thumb only.
It is an inter-species rule. It does not attempt to say there are not big animals in warm climates.

There were some 200 lb field dress deer killed in parts of South Texas back in the 60's and 70's in areas within CC and in wet years well before HF and feed was the craze.

We probably had 200lb hill country deer before fire suppression

redchevy brought up a great point. stxranchman, I'll ask you since you provided a great answer, was that the norm or the exception? And BOBO I don't really understand what you mean by that.

I fixed it I had a CWD moment.

Essentially the landscape has changed also, historically Hill country wasn’t a cedar forrest, and natural fires increased forage.

Modern Applications of Bergman’s are more generalizations because of changes.

Another example of a rift is largest Elk in North America are Rasberry and afognak island, but they are not native to the area, imported....

I use to think Predator wise Bergman’s was always spot on, except south east blk bears tend to toss a few wrenches in though,

I gotcha

I agree with this being a valid premise. Of course, there are exceptions to every rule. Lots of southern deer herds have had different genetics brought in, and deer breeders have managed their herds for larger deer. Pretty sure that sans human manipulation, the average deer size in southern (warmer) climates would be substantially smaller than their northern cousins.

Having said that, food plays a significant role. I have seen Arkansas River bottom deer (think soybean and corn country) that were almost twice the size of the mountain deer just 50 miles away.

So leaving out the protein feed and the exceptions to the rule in wet years, what would you consider to be an average weight for a mature south texas buck? Not the biggest one, but an average one? dressed or live?

Be ranch dependent, and all honesty with habitat manipulation it’s really hard to just give a blanket average. From my experience 170 -180 pretty easy. 200 would not be out of the question.

But at same aspect in northern panhandle we hit 200lb dressed pretty regularly.

Bobo, so 170-180 lb dressed?

I know you cant make a study out of our place, but Duval Co. is south texas to me. For the last 11 years our biggest bucks 5-9 years old have weight about 180-185 live. We are probably a little high on density, but we do feed over 10k lbs of protein a year on 300 acres LF and the neighbors feed free choice year round also.

Maybe I'm wrong, maybe we have way too many deer, maybe we are just in an area with genetic lines for slightly smaller deer, but for non protein fed non ag land, the 200 lbs dressed seems a bit high to me, especially for an average. I do know we have weighed every deer we have shot and the largest was 186 lbs 6.5 year old.

Not saying it cant be, just sharing my observations. I know if we could keep the population down a little more it might all be different.

For the years I hunted in La Salle County, mature bucks were averaging 220+. The heaviest I ever personally took was 245 live weight on the scales. They put out cotton seed as a supplement. The properties had agressive management plans to keep the population number down and the buck:doe ratio in balance. Guys often worried that management plan was shooting too many does, but there were always deer and they were in excellent condition. One of the harder decisions was during the extreme drought in 2011. We cut the population very hard so those left would have adequate food and water.

No, live. About what we ran in Webb. We culled pretty heavy for two years, so that’s 4.5-toothless, so that average is probably light, I bet it gets higher on the mature bucks going forward. Last one I shot was I think 7.5 year old, heavy rainfall year, and was 192 +- live weight I think (been 2 years) , If you are in the golden triangle of STX 200lb live weight would be pretty obtainable IMO.

I’m not a Stx expert, haven’t hunted in intensively enough to have enough long term data compared to what I have panhandle and hill country.

South TX is a large area. Hell in western Mcculloch we kill 180lb deer pretty regularly now, and that’s no protein, yet you go south east portion of the county and you are looking at 150lbs.

Ok thanks, we are not in the triangle but not far from it.

Remember a lot of these ranches will only have 1 deer to 20-25 acres or so native country no supplemental feeding.

Some areas are more dense than others but i remember as a kid we did a survey on my uncles place and on 1200 acres the biologist estimated there was only 50-60 deer on it


We have sold some country where it’s old family stuff not being hunted but not fed either and the numbers fall into this range as well


Deer have more food so they have a better chance of achieving bigger body weights

The Colombian mammoth is the biggest, then African elephant, then Woolly mammoth, the medium gray one is an Asian elephant.
There is a different rule of size at play with elephants, the larger an animal is, the better it can digest roughage.