A fair amount of research has been conducted on the economic losses due to pocket gophers; however, it is somewhat site- and region-specific and varies from year to year depending on the value of your crop. It is relatively easy to determine the value of the forage lost to pocket gophers. Botta’s pocket gophers at a density of 32 per acre (79/ha) decreased the forage yield by 25% on foothill rangelands in California, where the plants were nearly all annuals. Plains pocket gophers reduced forage yield on rangelands in western Nebraska by 21% to 49% on different range sites. Alfalfa yields in eastern Nebraska were reduced as much as 46% in dryland and 35% in irrigated alfalfa. Losses of 30% have been reported for hay meadows.
Calculating the cost of control operations is only slightly more complicated. However, the benefit-cost analysis of control is still not straightforward. More research is needed on managing the recovery of damaged forage production lands. For example, should pastures be fertilized, rested, or lightly grazed? Should gopher mounds in alfalfa be lightly harrowed? A study of northern pocket gopher control on range production in southern Alberta indicated that forage yields increased 16% three months after treatment. The potential for complete yield recovery the first year following gopher removal has been noted for a fibrous-rooted variety of alfalfa.
Economic assessment should also be made to determine the cost of no control, the pace of pocket gopher infestation, and the costs associated with damaged mowing machinery and/or mechanical breakdowns caused by the mounds. Assessment could also be made for damage to buried cable, water losses due to damaged irrigation structures, trees, and so on. Carefully survey your site and include everything affected by pocket gophers in your calculations.
From an economic point of view, here is the bottom line. Gophers eat alfalfa. The more gophers there are, the more alfalfa they eat. The more gophers there are, the more the field is criss-crossed with gopher tunnels (making the field full of tunnels that are energetically expensive to make for gophers but easy to maintain, thus preconditioning the field to future invasion). If you put in an alfalfa field, the best savings (both of alfalfa production and savings in gopher control costs) is in not letting the gopher infestation get large. Control gophers as they appear, along with gophers in a zone around your field. This way, damage is minimized (there is some evidence that an alfalfa plant, once the taproot is damaged, consistently produces less for the life of the plant), control costs are minimized, and the field is not preconditioned to future gopher invasions.
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Pocket Gophers
