Monday, September 7, 2009

Go Pher Them

Pocket gophers, with Botta's pocket gopher (Thomomys bottae) being most widespread of the five species found in California, are a gardener’s the greatest fear in the west. [Those who garden east of the Mississippi river are free of these elusive pests.] When the Russians settled just north of Santa Rosa on the coast in 1812, the story goes “we could have made a good living if it weren’t for the land rats”.

These pesky critters are burrowing rodents that get their name from the fur-lined external cheek pouches, or pockets, that they use for carrying, and short fur that doesn't cake in wet soils they dig and tunnel constantly. If they don’t constantly make tunnels their teeth will curl up toward the brain and pierce it.

They spend a lot of time on the surface at night and are the prey of barn owls. Many vineyards, in their futile attempt to appear environmentalists, build barn owl boxes. They don’t know that the great-horned has a territory of up to ¼ of a mile from its nest. The one near my house and next to a vineyard, has this large predation area and keeps out the barn owls. Ever year I hear the great-horned owl gradually find each other for mating with hours of hooting. The vineyard is 100 feet from my house. Not many barn owls near me. Furthermore, the usual diet for a barn owl eats only one gopher each night. Thus, the gardeners in my area have resort to trapping (killing) these “ground rats”.

Unlike moles, gophers “throws” or mounds are crescent- or horseshoe-shaped when viewed from above. [See the left photo.] Mole mounds appear circular and have a plug in the middle is more likely volcano-shaped. Unlike gophers, moles leave a raised ridge to mark their path. Also, moles are carnivores and gophers are vegetarians.

Pocket gophers live in a burrow system that can cover an area of 200 to 2,000 square feet. Feeding burrows are 6 to 12 inches below ground, whereas they nest and food storage chamber that may be as deep as 6 feet. [I’ve dug into food stashes of dozens of gnawed carrots.] Gophers seal the openings to the burrow system with earthen plugs. Short, sloping lateral tunnels connect the main burrow system to the surface and are created during construction of the main tunnel for pushing dirt to the surface.

The University of New Mexico says “… [gophers] may occur in densities of up to 16 to 20 per acre”. Ha! They’ve never been in my garden!

So, trapping is a must. The other photo is a eight-inch long gopher caught in a California box trap. These ingenious traps worked on the fact that gophers maintain their main “highways” six to 12 inches below the surface, not the surface feeding tunnels. If the trap is put in the main run with the metal strip on the top-rear of the box slightly raised and all sides covered with dirt. This allows air to escape but excludes light. Usually the gopher wants to protect its main “highway” when it feels air rushing out. Running toward the open hole, the gopher is in the trap before it knows it because there is no light to give it a clue as to the breach of the tunnel. Gotcha!

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