Tuesday, March 25, 2008

Gopher it!

It's spring, the young gophers are out, searching and fighting over new territory. The battle begins.

The earliest “modern” settlers of our coast north of the San Francisco bay were the Russians in March of 1812. They were gone by 1842. One anecdotal saying goes “we could have made a living if it weren’t for the ground rats”.

Ah yes, the hated gopher. These herbivores tunnel at both shallow and deep depths to eat on the roots of plants. An average of 22 gophers per acre translates into four pounds of fresh vegetation eaten every day—a rather healthy diet. It is thought that there are 1,000,000,000 rodents in California of which the most abundant is the pocket gopher. Large fur-lined external cheek pouches are used for temporally storing food. Thus the name pocket gopher, referring to these pouches, or pockets. Sometimes they collect pieces of roots, such a carrots, and stash them in a food reserve burrow for perhaps a truly “rainy day”. Many gardeners have watched a wiggling garlic top or freshly-planted lettuce and all of the sudden it is pulled beneath the soil. Fodder for the ravenous western pocket gopher.
(Those of you who live in the northeastern part of the country are blessed—no gophers. Skip the rest with delight.)

Gophers are very nocturnal creatures walking or skirmishing across the surface looking for new places to burrow. This is especially frantic in the spring, usually March and April, as young gophers go for their own territory. Once a gopher has a territory it maintains if for life. But for unexplained reasons, male gophers are polygamous which means their territories overlap or they wander at night to court their next “babe”.

The common gopher snake is thought of by gardeners as a hopeful controller of this pest. Alas, studies have shown that only 6.4% of the snake’s diet comes from gophers—better than nothing I guess. (Gopher snakes are territorial. So don’t try to move one form someplace to your garden. They’ll just wander off in pursuit of their previous home.) Rattlesnakes get only 2.5% of their diet from eating pocket gophers as the tunnel system makes it unlikely for them to coil and strike. The most significant predator, at 71.4% of it’s diet, is the barn owl which eats at night as the rodents scurry along the surface of the soil. The average barn owl will eat 155 gophers per year. Alas, if a great-horned owl lives within one square mile, the barn owls are scared away or eaten—something overlooked by the local vineyards that are trying to appear to be environmentally responsive by putting up barn owl nesting boxes near where great-horned owls reside.

In spite of the barn owls, most gardeners have resorted to wooden raised beds with wire bottoms—galvanized one-half inch aviary wire or hardware cloth. This doesn’t always stop them. A friend has vegetable boxes 12 inches high with wire bottoms. There was a gopher mound or “throw”, such as they are inclined to make when surfacing, up against the wood. He watched as the gopher merely climbed on top of the throw and hopped over the top of the board.

Wire baskets are becoming required planting additions for perennials, shrubs and trees. I once had a wire basket protecting an apple tree. The wire was four inches above the mulch. That didn’t stop a gopher from climbing over the wire to be encaged with all those succulent roots. The tree leaned over and simply died. However, wire baskets often work.

Lining the garden with a fence is trickier and riskier. Studies show that the fence would have to be at least two feet deep and up to seven feet deep in deep soils. One research study found gophers getting over a 10-inch high barrier! One recommendation would be that the fence would have to extend to 12 inches above the soil. Nothing is simple or safe!

I recently helped maintain an estate garden riddled with gophers. Even though all the dahlias were wrapped in 1/2” aviary wire, up to one quarter were destroyed by these troublesome varmits. I taught another guy on the crew how to use a Macabee trap—with its piercing tongs. After a month or so he had killed 100 gophers. So I presented him with a Macabee trap sprayed gold as a trophy. Sad truth was the owner stopped the trapping program. Gopher mounds showed up in her lawn and more dahlias bit the dust.

There is no silver bullet.

I must admit I find gophers fascinating, when I’m not cursing them, knowing that they must tunnel to keep their teeth in order. If unable to tunnel, their teeth would grow up to 14 inches a year in a curl that would eventually pierce their skull. Not a pretty sight. Although many gardeners would be delighted.

I’m always curious about their tunnel systems. The feeding tunnels, which terminate in a mound, are usually four too eight inches beneath the surface. The maintain “highways” used for routine travel are 12 or more inches deep. And gopher tunnels have been found at a depth of six feet. So I tried pouring plaster of Paris down a tunnel. I did get some of the plaster down to the second run. This mold of a gopher run hung from my ceiling for months.

After St. Helens, in Washington, erupted in 1980 it was the activity of gophers, their defecation, that brought mutually-symbiotic mycorrhizae to inoculate other plants for a better and healthier life and the restoration of the disturbed soil. (Mycorrhizae are beneficial fungi that extend to the root system of many plants to make it easier to gather nutrients such as phosphorous. Trees are especially dependent on phosphorous for good growth. Without the mutual symbiosis of the mychorrhizal association most trees would not prosper. The tree gives the mycorrhizae carbohydrates in exchange—this is not a parasitic association but is a two-way street for the benefit of both.)

Gophers turn over the soil more effectively than earthworms. And the mounds are good for the soil. One report (Effects of Pocket Gopher Mounds on Plant Production in Shortgrass Prairie Ecosystems, W. E. Grant, N. R. French and L. J. Folse, Jr.) states “…total above-ground plant production would be increased by roughly 5.5% by the presence of the mounds.” So they aren’t completely malicious critters with no worth what-so-ever.

I still hunt these “ground rats”.

Please leave a comment - I'd like to know what you think.

Visit my web site to learn about my gardening books.

Note: I seem to have lost the usual way to leave comments. To do so, either click on the "___ comments" button or click on the title of the blog under "Blog Archive". Thanks, Robert


Anonymous said...

For the past few months, I have been battling a CaddyShack gopher. Originally, I purchased 3 gopher stakes to drive it away because I didn't want it's death on my conscious. Last week, as I was walking across the grass to retrieve my Sunday paper, a gopher "highway" as you call it, collaped under my foot, resulting in a broken metatarsal bone. Today, I declared war and purchased a metal gopher trap. Gophers are destructive and need to be eliminated.

gk in san diego said...

I had gophers destroy a Tipu tree I raised from seed. I just put in a second tree with a wire cage around it and am keeping my fingers crossed. I'm about to plant 2 more trees, a Strawberry Madrone and a Purple Orchid. Is there any information you know about what kinds of tree roots they like? I'm worrying about the wire cages restricting the growth of the trees.

Toby and Me said...

Thank You for a great website. My Son and I, found some Pocket Gopher Fossils. They were injured by Large animals stepping through there burrow as well as snake encounters. The perfect condtions
exsist for the gophers to fosslize where We found them.

As You have experence with Pocket Gophers, I thought You might be interested. I have some pictures gopher fossil's here:


Carol Marie said...

I live in central arizona ... lots of pocket gophers. I had briefly considered trying to eradicate them until I had a upclose and personal encounter with a young one. We had unknowingly flooded his feeding tunnel and he came up for air...he was wet and disoriented as he searched for another area to tunnel into...he was unsuccessful in his attempts. I became concerned for him because we have several dogs, I wanted the little fellow to at least have a fighting chance...we kept him in a cage overnight and placed him back in the same area the next day. I have footage of him re-excavating his tunnel. Now, in light of that experience and with the added knowledge provided by your blog ... that they are beneficial (I use the soil from their mounds for planting~great top soil)...I am content to find ways of co-existing with these fascinating little creatures.

Walrus said...

I bought a device that attaches to a tailpipe so I could gas them. It blew off of the tailpipe with a loud backfire. My tundra truck is more valuable than my roses or trees.
I just heard from a pest control contractor that he can no longer use the poison pellets near homes. He saw a 2 cycle gopher gassing machine in the southern Calif. AgAlert weekly magazine. I need something that works that won't kill my dog.