I just saw an otter (or possibly a mink) - how do I protect my livestock?

We are in otter and mink country - both of which have been known to break into henhouses and eat chickens.  What I saw was from a distance, a very dark, black/brown coloured creature, about two to three times the size of a feral cat, inch-worming it's way from the pond to the woods.   I'm about 75% certain it was a river otter due to its size and shape.  The mink here are much smaller and have a thinner body to length ratio.  But it's a good reminder to spend the day doing any repairs on the duck/hen/geese houses so that they are proof against both mink and otters.

Any tips or tricks for mink/otter proofing my critters?  How do they differ from racoons in the way they get into houses?  At the moment we have two locks on each door because the racoons can often get one open.  Do otters/mink dig under walls to get at animals?  Will they take on a goose?  Do they climb walls?

I have some friends up on the Little Red River who use 1//2 inch heavy gauge hardware cloth to protect their chickens and ducks from the otters and minks.
They have the wire buried about 1.5 feet deep all the way around their enclosure and they lock everyone in at dusk (for the coons).

I have seen otters and mink dig, so I imagine they would dig to get under a fence.  My friends have not had any losses to these critters since they buried the wire around the perimeter.

Note: otters will also chew wood to get at food, so you may need to add a metal strips to any wood framed door that is the entry way into the pen.

Redhawk

Based on your description, I agree, it would likely be a river otter...but a very small or young Fisher could also qualify.  The key here is to critter proof for all critters at once.  Mink would be the best animal to use as the base animal to protect against, as they are the tiniest and the most voracious/destructive to poultry.  

There are two basic keys to prevent livestock/poultry predation:  Barrier or Fencing that is electrified or metal or physical deterrents such as livestock protection dogs, scent deterrents, etc. that cause the predators to CHOOOSE to stay clear.  I will focus on the barrier or fencing methods.

1)  Take a good look at the construction: is there a gap where at the soffit (where roof meets wall) spaces?  If so, cover with heavy duty, hardware cloth (1cm, square openings, welded wire).  Do not just staple the wire, take 1x2 wood and SCREW through wood, through wire, into building.  This ensures it will not be easily removed by predators.

2)  Take a good look at the FLOOR: is it concrete, or heavy wire surfaced?  If not, critters can dig beneath the wall and access the enclosure.  Ideally concrete, it has the advantage of being critter proof and easy to clean.  If not use very heavy gauge, small opening wire such as hardware cloth on the dirt/gravel floor, attached to the walls so that it is sandwiched between wood (staple up wire, then use 1x2 over the stapled edge and screw, not nail, in place.

3)  Take a good look at the walls: are they wood?  Are there any gaps, rot, or soft spots?  Ideally, cover or replace all wood within four feet of the ground with metal roofing (perfect use for used metal roofing) SCREWED to frame, it will not rot or deteriorate and, at four feet, is climb proof for most critters.

4)  Fencing:  chicken wire simply traps poultry, it in no way protects them from predators.  Predators will climb, tear or shred chicken wire.  If wire is to be used as a barrier it must be hardware cloth or aviary wire - this is heavy gauge, tiny opening (1cm or less/1/2 inch or less), galvanized mesh - this is strong enough but is still climbable so it must be electrified or stop at a solid or equally secured roof.  Again, used or new metal roofing can be used for fencing or wall panels, and will generally deter most but the largest and most acrobatic predators.

5)  Take a good look around the exterior of the enclosure:  are there trees, fence lines, buildings or other items that would allow a predator to circumvent your precautions?  No point in making the fence climbproof if the predator can fly in the open top or climb up a nearby tree and "drop in".  This includes machinery (tractor, truck etc.) that may only be temporarily an access point for predators to enter the enclosure.

6)  Take a good look at the entire property:  most predators prefer cover, ensure that there are large, cleared areas near your livestock so that you are not offering coverage for lurking predators.

7)  Electric fencing will prevent most predators from accessing enclosures.  Although expensive up front, and somewhat labor intensive to maintain (keeping area free of foliage so fencing is not "grounded out"), when properly installed (multiple lines every four inches up to a minimum of 3-4 feet) it is likely the best longterm protection available.

Good luck, hope this helps!

Mink, at least here, don't get anywhere near that big.  That said, Bryant's suggestion is the way I would go.  If you can't dig down because of rocks or time or whatever, I have kept dogs from digging under a fence by laying hardware cloth or chicken wire flat on the ground a foot and a half or so out from the fence and pinning it down.  You also fold about 4 inches of the chicken wire straight up and attach that part directly to the fence.  The dogs couldn't figure out to start digging that far from the fence and couldn't dig right at the fence because of the chicken wire so they gave up.  I'm not sure if that would work for otters, but I would sure try it until I could get the fence dug in and buried all the way around.  You can do a pretty long fence with that method in a very short time.  If you use hardware cloth, you could reuse it as your buried fence as you get a chance to dig.