The general consensus is that northern WI rats are smaller, thinner skinned or pelted and yes many are caught earlier as well. I think the real testimony regarding the quality of northern WI rats was a couple of years ago GWF put out on their route promos they would not take northern WI rats in the round or not put up. Now the huge question is what and where do "northern rats come from? I think the biggest reason from my experience is that in the north rat habitat is more sedge, bullrush and other northern WI plant food and not cattails nearly as much. Less food and lower quality. I don't know about genetic differences.

Bryce

apparently not driving south to their cabin once they're froze out up here

I am not sure what you consider as a northern Wisconsin rat Bryce, but the muskrat I catch here in Rhinelander seemed as heavy furred and thick skinned as any muskrat I have caught or seen throughout this country that I have traveled and trapped for the past 40 years! I can name a lot of areas that the rats look a lot thinner skinned. Smaller rats too? I will compare rats with anybody that wants to compare and I will bet size wise the rats up here in northern Wisconsin are as big or bigger! Are you familiar with Bergmans law? You seem to paint with a pretty broad brush!

Chris

Some interesting points raised.

I was thinking about Bryce's comment about when GWF put that disclaimer on their website. They know what they are doing so I figured they must've had a good reason for posting that about selling in the round. Hmmm.

That is why I asked the question what is a northern WI rat. Ask GWF they were the ones that made the statement. I am sure they have a better answer than I do.

Bryce

Northern WI rats are just like ND rats they both have thin leather. And When trapping In Oct In northern WI your trapping a whole bunch of young of the year rats that haven't matured yet. It takes some time for a young of the year rat to make some leather. And It also has a lot to do with the habitant they are taken from.
Your best rats are those that are taken just after the ice goes out. or the ones taken through the Ice late In the season.

Yes very familiar with Bergman's Law as it was part of my ecology studies, but I have some experience in catching, sorting and shipping northern rats versus my central rats and some more southern rats as well as pond, river, marsh, slough etc.
I have some places where my average rats size runs bigger but it is on my river line where there are fewer rats and many fewer younger rats which I attribute to higher levels of natural loss as there is much more edge area per acreage of cover than in larger bodies of water or very large marshes.

Bryce

Bergmanns law doesn’t apply to rodents

If you think about it they are generally born later and harvested sooner. So fall rats would likely be inferior. Spring time gives them a chance to catch up.

What source do you have for that statement? In the college I graduated from we specifically studied the relationship between warm blooded mammals from multiple species both in northern climates and down in southern climates. Direct correlation with body size noted with rodents as well!
http://www.newworldencyclopedia.org/entry/Bergmann%27s_rule

Chris

Experience

Here in wi southern marsh rats will be larger and average more than up north rats. Beaver ( yoy) in southern wi generally run a few pounds heavier too. The way it is. If you don’t believe me ask any fur buyer that has experience with both. Your mink run smaller too overall. Even smaller in the UP. Well furred tho.
This is a generalization, I’m sure there is isolated pockets that break the trend.
Bergmanns is just another wild things rule that is broken.

Hodag, I'm approximately 2.3 degrees latitude north of you, 4 degrees north of the Horicon. A degree of latitude is approximately 69 miles. I've caught quite a few rats from the Canadian border of MN to the Iowa border, most of them in winter.

Now what's my point you ask? Bergman rule doesn't apply to muskrats!

Correction <aquatic rodents> Perhaps wintering in a controlled environment is notable?

As my “experience” is limited to this.
I am a firm believer that muskrat size is a direct result on the quality of their diet. Diet also influences reproduction. However diet is only one piece of a delicate puzzle that makes a muskrat(s).

Rats and beaver is all diet quality and quantity.

Our river rats are the biggest for me where they are in the corn, soybeans and freshwater mussels.

all I've got to say is look at Dane County.....sportsmen down there better get their crap together....they are the leading front to ANTI's

Why was End trapping on public lands voted on twice in Dane County

Probably submitted by 2 different people. I don’t think that one will get far in the fur harvest committee

look at all those anti resolutions.....they are putting in real effort...they want Wisconsin to be like Commiefornia