Ever wonder how old the average furbearer is...I do. It would be interesting to know. I suppose DNRs done some studies.

I make an educated guess at k9 age for my log book.
It has helped me see that my older k9s mostly come from pee post and blind trail sets. Remember I'm guessing on age. Just using teeth to age.
Still a work in progress. I hope to keep learning till I find the end of my line.

Several studies, some more formal than others indicate for most species common to WI like coon, fox, coyote etc. that about 60% of the catch is YOY. For rats the average age would be younger and for beaver it probably is a good year or so older as the young don't disperse until 2 years of age. I don't know if this follows through for cats, fisher etc.

Bryce

When managing the furbearer resource on a trapline it is imperative to know how to differentiate between juveniles and adults for certain species.Recording the numbers is imperative to good management for species like marten so you know when to stop trapping.
In general most animals caught in the fall will be juveniles.Later on you will get a much higher percentage of adults.

For beaver you can target primarily adults by choosing location. My harvest does not reflect the age of the beaver population.

The law of averages would say that the majority are the young of the year or last years young.

Every now and then catch one that is completely shot in the teeth and you can know that it is very old. The ones I have caught like that were always going into a place that had not been trapped in many years.

Targeting mature colonys at the house you get the whole age spectrum.Which is OK you get some to ship and some to use.
Trapping newly established colonys each year will get you a pair of xl beaver at each house.

They age bobcats here.Mine have ranged from .5 to 12.5 years old.

I've had several bobcats (from Michigan) that ranged from 5.5 to 8.5 years old. The wolf I got in MN a few years ago was 4.5.