Researching the Enemy
I have a rare opportunity, a day off from working. I spent two hours of it today researching the topic over 30 websites and forums, two of which were government reports, and have the following to share. Of these, three pages were **extremely** helpful in separating the wheat from the chaff, PM me for the URL's.
To Jane_Doe, sorry this won't be of much help, none of these methods include keeping the little buggers alive (with the exception of the methods to drive them away or fence them out.) But I found a lot of interesting info on gopher eradication.
Know your Enemy. The first step is understanding what you have, as treatments and methods are very different. Moles leave a small volcanic mound with a hole in the center; gophers push up crescent shaped mounds and plug the hole behind them. I have pocket gophers. This is what I researched.
Also it's important to know that if you drive out/kill one gopher, others will move into their territory and use the same tunnels.
When employing any of the methods mentioned, USE GLOVES as these guys are extremely sensitive to human scent of any kind and will avoid any area with it (which is a good vote for the urine approach.)
What may or may not work.
Time and time again, the following methods are discussed and may or may not actually work. People rave their method really worked (see my post on the chaser! :-) ) but none of them are proven or verified by any professional source. Among these are:
"Electronic" sticks: Gophers don't scare easily. These are claimed not to work. But in my personal experience, they do annoy them out of a given area. So if you just want to keep them out of a garden, this may help.
Gopher fences: Dig down at least 24" around your garden and fence it underground, leaving 12" above ground so they can't jump over. Whew, what a lot of work.
Scent-based approach: Ammonia, human urine, or commercial pellets with fox urine.
Non-toxic spraying: Another approach is a castor-oil based treatment. The oil covers the food source (grub worms, insects, etc.) and gives them "intestinal disruption." They associate that territory with the belly ache, and move away. This is a long-term solution; it takes three weeks or so to start having effect and needs to be re-applied every few weeks. Worse than dandelions!
Poisons: discussed, and effectiveness is not proven.
Burn 'em out: I even found a source that sells a device that pumps propane and oxygen into the tunnels. When you begin to smell the propane, an igniter in the device blows the little buggers to smithereens and collapses the tunnels, preventing newcomers from using the same tunnels. I've even seen suggestions to pour gasoline into the tunnels and "carefully light it." Please report back if you try this approach and survive, we will nominate you for the Darwin awards.
Chewing Gum: of all the unproven methods, this one seems to show some promise, I have seen many unrelated sources claim it works. Get a pack of Juicy Fruit gum, put gloves on (see scent above,) open the pack, roll up a plug and throw it down the hole. They eat the gum and can't digest it. "Death by constipation."
Drowning, smoking, or other hole-chasing: With new visitors, a garden hose down the hole may drive them out (have a shovel handy for the satisfactory head whacking that follows) but in older systems, it will never work. Gophers can move up to one ton of soil per day. This is not a frugal claim, this is directly from one government reports I found. So an old system will never fill up; additionally, the nest chambers are always higher than the rest of the tunnels. They'll wait it out and watch the river roll on by.
As mentioned, gophers are industrious tunnellers; as soon as they sense an odor they plug up the chambers in no time. Smoking or noxious gas approaches will have only sporadic results.
Ground glass: One person mentioned they had an area where gophers would never go. Turns out it was a family dump before his house was built and it was filled with broken glass. He put ground glass into holes and under his new shrubs and the gophers went away. Interesting approach, who knows.
What absolutely, positively works
Repeatedly I came across one method used by professionals, and is mentioned again and again as the best method, including the government report pages I found: trapping. Of the gizmos out there, there is one trap, created in the early 1900's, that is still useful today: the Macabee style trap or imitations. If this trap is not working for you, read on, it may be how you're setting it.
Similar to a mouse trap but not, the Macabee is designed with the arms/prongs on the sides instead of a single bar that swings over the top. The actual trip is at the back of the trap. Because gophers push soil ahead of them when clearing out a tunnel (see "know your enemy",) just about when the soil hits the trip switch, their head/neck is lined up with the prongs and it snaps shut. They never see the trap because it's ahead of the dirt they are pushing.
Key to making these work is understanding the pattern you see above ground. The crescent shaped mounds are an exit hole leading to the main runway. Usually they will go straight(ish) down for 4-12 inches to the main runway, something like
runway <---- ¦ -----> runway
with the vertical pipe representing the exit hole directly under the crescent-shaped mound.
What you must do is properly identify where the runway is and dig down so you can see it in both directions. That's the hard part. PM for links to two excellent guides that display how to locate the runway and how to set the traps.
Once found, you need two Macabees, one in each hole. Chain/string them together end to end, with the middle of the chain staked nearby so they don't drag your traps down the hole.
This part is important: cover the trap area with a board, then cover that with dirt so no light enters the tunnel. Gophers become very suspicious when light or air enters a tunnel where it shouldn't. Contrast this to some traps that have an open end, and claim the gopher is drawn into the trap because they want to close up the opening.
I was off to the hardware store but checked our shed - it appears I have two perfectly good Macabees, old ones, in my shed, inherited from my wife's dad. I'm off to git me sum gofers . . . will report back on the effectiveness of "superior firepower."
Superior intelligence remains to be proven . . . .