That is odd on the single female. Can't say I've ever ran into that. The multiple female thing is becoming quite common it seems. I wonder if nowadays since trapping is more for nuisance than fur, especially in the south, if nature is producing more females than males, one male can breed multiple females, to account for the endless pursuit of them? Although this would go against the narrative of monogamy amongst beavers. I wonder if boco runs into this since he still is able to manage his line.

Giant Sage/Rich, I guess the only difference would be that in some cases as mentioned SOME of these colonies of beaver have been managed throughout the years...really no explosion so to speak.
No expert here either, but as mentioned I have an area far North of me that has had a bit of a population bump, but the area has been trapped for years. One creek that I told Jackie and Eric V. about has kicked out over 20 beaver so far this year. I caught 15 on a nuisance job in October. Of the 15 I had 6 females that ere 45+ pounds but only one was prego. the rest were 40+ pound males that ranged up to 65 pounds. Our fur season opened up in November and I again scouted the area after the dam was opened and saw fresh sign of beaver?? Caught number 20 yesterday. I believe that the dry Summer we had had these beaver colonies pushed together out of necessity. No bites marks or damaged beaver so far on these beaver. In two other areas close by to this creek, I had other nuisance jobs and caught typical families numbers of beaver...6 and 8. AND there is another trapper that catches beaver up there every season. My thoughts lead back to these "conservation or protected" areas our county/states sets aside that are not being managed. the public ends up footing the bill for ALL of these nuisance animal issues that occur. Leave it to government.

I wonder what the ratio of male vs. female per litter? Maybe there is a way to sex the embryos, of pregnant females caught, to get an idea of the make-up of a typical litter.

I never took the time...just noticed the number big old adults...and scratching my head.

Just ran into the same thing, one large single female from a spot that I removed two in the spring.

Small pond, on a large nuclear plant. 2 years ago removed one 3X large male, this summer removed the classic breeding pair of two year old's. At that time the lodge was mudded but obviously no feedbed. Just last week (end of January) site called me again, more beavers in the pond. Showed up and there is a dinky feedbed in front of the lodge.

1 3X female was all that was in there and she moved in sometime between September and beginning of December based on when the ice came in. She was definitely not a two year old.

Took 21 beaver out of one colony once a long time ago.
There is a live colony on one of my traplines with 4 live houses on the pond.It is in a muskeg swamp with lots of cat tail and shallow water.
I only trap that pond every second or 3rd fall and usually take 2-5 beaver there each fall I trap it.

I'm no expert, but in my trapping on big rivers I'm blissfully unaware of "colonies" of beaver. It's wall to wall beavers for 150 miles of river. The kits (which I largely avoid) are usually LM's with a few mediums and seem to stick close. So when I catch one I pull the trap not to catch the rest of the siblings.

So I guess you have never seen a castor mound and dont catch any scarred beaver?

I trap irragation ditches and small rivers(2), when I first started here in the mountains, I would catch one or two at a location and it would go dead. Then I would find sign at another location maybe catch one or two and then nothing. I now set up and down a few hundred yards and will catch them leaving,( I think its the ones bailing from where I find them). I've also had them set up housekeeping in the dead of winter, I was running snares for coyotes one winter and the second check my snares were under water. When I trapped in NY I didn't see this behavior, I caught a big female last spring, the first animal in the colony, that was the only beaver I caught there, i had the traps there a month! The longer Iam at this the more surprises I find. I guess you don't know what you don't know?

Do the large adult males go on a swim-about during breeding season?

I'm not talking about the single males....I'm asking abouthe males that are paired up with an adult female. Will he breed and leave her at that lodge/den/dam, etc , travelling to another colony to attempt breeding with any other adult female? You know...like buck deer do....travel fom doe group to doe group.

If this is common then that would would explain why I'm seeing several lone adult females right now. The male may or may not return. If he does...then a trapper would say I have a breeding pair there. If he doesn't...trappers says only an adult female there.

I have always thought the pair stayed together....maybe not. Those males are looking for other females during breeding season.....not satisfied with just one female. They are like most mammals.

Great question...thinking like a canine...YES...thinking like a rodent....definitely!

oOne thing I have noticed the larger the body of water the more beaver and of coursethe higher number of beaver I took 13 large beaver from one hole 0n lake Eufala it is a big flat lake 105,ooo acres also the big slews in Deep Fork bottoms can hold big numbers of Beavers Especially in wet years.

I've wondered if a pregnant female gets to hard to live with and the male sets up temporary shop elsewhere until the birthing is done.

I've wondered if a pregnant female gets to hard to live with and the male sets up temporary shop elsewhere until the birthing is done.

Yep i see that alot, he won't be far just not living in the same house with her and the kits. Be a ways up or down stream from the main living quarters, all that fussing gets on his nerves, lol.

How do you avoid kits when it’s ’wall to wall’ beavers? What does close mean when they are that thick? You pull ‘the trap’ once you catch the one? You only set one trap per 150 mile stretch?

I don’t think like that. When I set beaver traps, there are no survivors.

Good question(s). First, I try to avoid areas that appear to be denning areas where I see multiple foraging trails in a small area or other signs that show juveniles in the area. (I learned a lot from an older trapper that used to trap the same river). Second, I focus on setting established marking areas that are mainly visited by adults. In a 10-12 mile stretch of river I only set an average of 1 trap per half mile depending on how much activity there is. Finally, the proof is in the pudding...of the first 92 beaver I caught this year all but 11 were XL or larger. When I do catch a juvenile I usually just pick up that trap because in my experience chances are good I'll pick up 1 or more siblings in the same set. Since I'm a fur trapper not ADC I prefer to leave those for next year.

I guess that was directed at my post?

Does an adult beaver that marks his/her territory mean that he/she is a colony beaver? In my experience colony beaver are isolated by some distance from another colony and usually found in ponds and small creeks with dams and such and don't seem to fight with each other. Pelts are pretty clean. Everybody gets along.

The river beaver I trap are fighters and most scarred up bad. The river often floods and beaver move great distances during these events...I'm not sure that I could recognize if there are family units that stick in small areas of the river habitat. I just see constant moving around and if I trap out an area early in the season by late in the season it's likely occupied again with new beavers.

I have read somewhere that beavers mate for life, but I don't believe it. All the adult females on my lines are pregnant by mid-march. Even if I trapped out their mates in December..

In Minnesota, when the water open up in the spring the first run or two will be dominated by big adult males. Weather they are protecting their territory, looking for a new or another mate, or just trying to get out for some fresh air and food, they are out and about first. When there is fresh castor around it can go from no castor mound around to dozens over night so I always assumed it was a territorial thing. I try not to trap colonies at the same time of year, so I don’t really know the number of single females in colonies. So it could be due to that male either being gone for a little while, got killed in its travels (trappers or predators), or maybe found a new mate/place to call home.

When I have trapped down south during breeding season there is an movement of beaver, and lots of fighting taking place that is very similar to what I see at ice out in Minnesota. In both places a little rain or higher water seems to drive the beavers to move more.

Scent mounds are a different thing than a castor territotial marking mound.
Scent mounds are made by 2 year old beaver advertising for a partner to pair up with.After they have paired up,they will not mate until the following winter after they have established a home range.For the most part,the only beaver that mate in spring after ice out (late april early may here) are females or males that have lost their mate after freeze up and have not had another beaver available to mate with in feb under the ice.From my observations over the past 50 years or so they are not often sucessful at finding a mate that late unless they can hook up with another loner that has had a mate trapped in winter.Beaver who mate late are the ones responsible for the cub beaver that are sometimes caught in fall,because the late mating has produced a late litter.Scent mounds are only found in spring right after ice out here when the 2 year olds are on the move.Other beaver move at this time also,sometimes entire colonys will move when feed has been depleted in an area,and fighting is common when they move thru other beavers established territory.Beaver here do not often winter in the rivers,because the rivers often flood here late in the fall washing away feedbeds.They will be OK if they set up in a bay,a backwater or tributary.The beaver do use the rivers extensively in the spring for dispersal.Medium sized rivers here are like beaver highways in spring and plenty of beaver can be trapped on them in a short time without having to move traps.
Scent mounds are easy to distinguish from Territorial castor mounds.Scent mounds are small and almost never covered up by other beave,Other beaver will leave their own scent mound close by and at these places there can be many small scent mounds several feet from each other usually along a flat bank.
Territorial castor mounds get pretty big sometimes because beaver from two (or sometimes more) colonys use them and cover up the other beavers scent before adding their own.When beaver are trapped out of one colony and no longer mark the territorial mound,the neighboring beaver will move in to the vacant territory.
In good habitat here ther can be as many as 4 live housed on a mile of stream.Way up north near the treeline where beaver live on willow the density is much less.perhaps one live house on 10 miles of stream.
This is what I see in North eastern Ontario.