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Providing evidence to improve practice

Action: Pest regulation: Exclude grazers Mediterranean Farmland

Key messages

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Pest regulation (0 studies)

Pest damage (1 study): One site comparison in grassland in the USA found no relationship between plant numbers and gopher numbers in ungrazed sites, but found fewer plant species in grazed sites with more gophers.

Ratio of natural enemies to pests (0 studies)

Pest numbers (1 study): One site comparison in grassland in the USA found more signs of gopher activity in ungrazed sites, compared to grazed sites.

Natural enemy numbers (0 studies)

Supporting evidence from individual studies


A site comparison in 1991 in annual grassland on the Central Coast, California, USA, found more signs of pocket gophers Thomomys bottae in ungrazed sites, compared to grazed sites. There was a correlation between gophers and plant species in grazed sites, but not in ungrazed sites. Pest damage: In grazed sites, fewer plant species were found where there were more gophers. However, in ungrazed sites, no relationship was found between gopher numbers and plant numbers (data reported as statistical results). Pest numbers: More signs of gopher activity were found in ungrazed sites, compared to grazed sites (5% vs 2% cover of soil that had been dug up). Methods: European domestic cattle were introduced to Monterey County in 1770. In 1937, grazers were excluded from one landscape (the Hastings Natural History Reservation), but not from a nearby landscape. In 1991, 43 sites in the ungrazed landscape and 37 sites in the grazed landscape were sampled (methods not clearly reported, but the cover of gopher tailings was measured in 20 x 50 cm quadrats in a different part of this study).


Referenced papers

Please cite as:

Shackelford, G. E., Kelsey, R., Robertson, R. J., Williams, D. R. & Dicks, L. V. (2017) Sustainable Agriculture in California and Mediterranean Climates: Evidence for the effects of selected interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.