Species Specific Beaver Trap
As is, the 12x18x39 Comstock swim through beaver cage trap will take beavers, otters and muskrats.
Beavers may be taken alive when the Comstock beaver traps are set slightly out of water, an inch or two above the surface. This, of course, means that all non-targeted species will also be alive and can be released. I have released otter and muskrats.
When beaver trapping in a situation where taking live beaver is not required, where the traps are set fully submerged, it may be possible to take beaver only, while allowing non-targeted muskrats and otter to escape alive.
The cage wire is 1-1/2 inch mesh. Having not tried this yet, the size of the opening or openings would have to be determined through trial and error, but I believe that a 3×6 opening would allow all muskrats and probably most or all otter to escape. By cutting a hole or holes in the top of the cage when set upside down, small animals like otter and muskrats would go out through the mesh. At the same time even a 3×6 opening would be too small for beaver pass through.
If a flap was connected next to the opening, the traps would not have a single option, but the option to be used either way to take beaver only with the flap open and beaver, otter and muskrats with the flap closed.
The only negative to having this opening is that the traps will appear to be “sprung” from time to time when smaller muskrats and otter fire the trap and then escape. Unless there is a trial cam at the site, there will be no way to tell what took place.