Hmmm....the pig snares being "a very high volume payoff for the work involved". It depends how you look at it.
I set my first pig snare maybe 35 years ago. I caught my first pig maybe three years ago. Sure my first efforts weren't that serious, and I did very little in the way of setting pig snares in the 32 years in between...but I guess my point is you don't always get a pig when you set up a snare.
My first pig.... the one I posted a picture of a while back, was a pig that had moved on to a neighbours farm along with a few others. I spent a long time out with a gun trying to shoot them. A couple of times I was only a few feet from them as they rooted about in the thick scrub, but I couldn't see them to shoot...even though the bushes were shaking and I could hear them chomping.
I tramped up on to that farm maybe twice a day for maybe two or three weeks before I snared that pig. The pigs were moving around a comparatively big area, and there were only a few places where I could set a snare. And compared to some places you would say that the pig population wasn't very dense....and this of course means a reduced chance of catching a pig if that is how you look at things.
At any one time I may have had 10 snares set. I would take bags full of apples on to the property and lay them out in the hope that I could get the pigs returning to certain spots on a regular basis. I set up a game camera, and managed to get a photo of a pig on the first night, but I certainly didn't snare one on the first attempt. So I burned many calories of energy and spread dozens of apples in the time leading up to the capture. I also managed to catch two of the farmer's dogs in spring-up traps that I set....fortunately neither was harmed. I had set the traps to only tighten the noose... not launch small animals into orbit.
The evening of the capture was wonderful. I was doing the rounds of my snares, and when I heard some crashing in the bushes I got fairly excited. I approached the snare and saw the awesome glossy black boar with a noose around his neck. He wasn't struggling much, but he was pulling pretty hard on the rope and had managed to smash off one sapling tree of about two inches in diameter. Anyway, I speared it in behind the shoulder and it died quickly.
There have been pigs in the same spot up until recently, maybe there are still some there although they aren't leaving much sign. A pig hunting acquaintance of mine had been trying to get them. He even built a steel cage trap which he had set for a while without success. Anyway he was having a beer with some mates when a member of the family announced that they'd just seen a pig. So the only guy that hadn't been drinking was nominated the shooter and they took off to where the pigs had been spotted. He shot both of them....and I believe one of them may have been the original one that I got a photo of.
On the other hand, the last big pig I got was a pretty good payoff for the work involved. This was caught on some family land where there can be a relatively dense pig population from time to time. There was a well-worn track that they had been using. I set the snare and caught the pig on maybe the second or third night.
Dang that rebar deer trap sounds dangerous!! I have seen pictures of what I think is probably a similar trap in a book I have somewhere... and on the internet....but in my version a sharpened stick is used and it is referred to as a pig stabber.
Thanks for the info about the coffee can traps. I have long been fascinated with the concept of a foot trap, but yours is the first reference I have seen to one being used for hoofed animals in modern times. I imagine that the poacher probably had a snare laying over the hole in the can so that the leg would be held securely as the deer moved away with the can on its foot.
Here is a similar can arrangement evidently recommended for big cats:
http://wildlifedamage.unl.edu/handbook/handbook/allPDF/ca_c93.pdf - you have to scroll down to see the picture of the coffe can trap.
And I guess the earliest design of a foot trap looked like the one shown here:
http://southernsudan.prm.ox.ac.uk/details/1920.61.2/
I wish I could post the pictures for you directly, but I haven't figured out how to do that yet. Doc knows how to.