Hi Rainier,
I used GopherHawk traps to successfully re claim most of my pastures. I ended up purchasing about 10 of them along with a tulip auger for my cordless drill to set them and a camp shovel to dig up sprung traps. I stopped counting at around 70 gophers and I hated every minute of it. Not all of those caught were cleanly dispatched. It was a lot of work and unpleasant to boot but it was effective. I didn’t get anywhere with box traps, flares, or exhaust gas by comparison.
This last spring and most of the summer I was completely out of commission for various reasons and apparently I have dozens of new gophers to deal with so it’s a never ending process if your pastures are “quieter” than your neighbors. I read somewhere that it takes roughly three years for a tunnel system to collapse so perhaps if I had been more consistent they would have been slower to re occupy.
One helpful addition to my gopher control has been really aggressively dragging the mounds. If I can level the area before the rainy season and spot seed my pasture stays smoother and nicer overall. The tractor helps collapse the shallow tunnels as well.
Completely random aside…I watched with complete fascination one winter afternoon as a blue heron very expertly tweezered out and ate three gophers from my largest pasture. It stood stock still for what seemed like hours over the mound…then bam…down the hatch! I was a fan before but what a neat bird. Now if I could just rent a flock of them…