For everyone with gophers, I highly recommend against using any type of poison. The gophers have probably already tunneled beneath your house and you would not want a rotting gopher smell eminating from your foundation. I would also believe that poisons may be taken up by the roots of nearby plants.
I had a serious gopher problem at my old house on the side of a canyon and I was finally able to get rid of my gophers. I did it by using the cheap metal gopher traps at Home Depot. Simply place one trap in each hole that you see, bury it of course and I also recommend staking it to avoid having the gophers drag it off in case only part of its body gets trapped.
I kept ignoring my gopher problem and by the time I decided to take action, the gophers tunneling had already damaged my foundation. I know this b cause I lit one of those gopher smoke bombs and hurried it in one of the gopher tunnels in my front yard and I had smoke coming into the middle of my house through the foundation.
For those of you that think you have gotten rid of all your gophers, think again. You may have captured all the gophers in your yard for now but the tunnels are already built and gophers from the surrounding environment will eventually take up residency.
Once you find out you have gophers, you need to take immediate action. The more tunneling the gophers do in your yard, the higher the probability of other gophers inhabiting your yard after you rid yourself of the current gopher problem.
It will be an ongoing battle once you kill off all the current gophers, there may be periods of months to years where you will not see signs of gophers but they will come back. I've helped so many of my friends with their gopher problems that I've even considered starting up a gopher killing business:)
Simin