Wood rat -Neotoma fuscipes (Baird), is the brown-footed wood rat also known as "pack" or "trade" rats. They inhabit the foothills and lower mountains. This species has a body 7 to 8 inches long and a tail 6½ to 7½ inches long. It has a blunt nose, slightly haired ears of medium size, brown fur, and moderately haired tail. This rat builds large, conical nests of sticks and litter on the ground or in trees and buildings.
Red fox squirrel - Sciurus niger refiventer (Geoffroy), is an accidentally introduced species. It feeds on walnuts, avocados, and oranges. It may be trapped with an extra large type of rat trap placed in trees.
Meadow mice or voles - Microtus are injurious because they gnaw the bark and roots of avocado trees that are surrounded by grass and litter. Their runways may be found in such locations. Mousetraps baited with oatmeal, rolled oats, or bits of apple or carrot may be set in these runways with the triggers of the traps across the runways. Mice running in either direction can then be trapped. When large numbers of mice are present, it may be more advantageous to poison them.
Pocket gophers - Thomomys spp. Are destructive to young avocado trees and their control demands continuous vigilance on the part of the grower. Their presence is indicated by a series of rounded surface mounds. They are best controlled by trapping or poison baits. The secret to using traps and poison is to find the burrow running in both directions below the mount - 8 to 12 inches deep. Clean out the burrow and place trap or poison in each direction. Cover with paper and soil to exclude light. This is important, for if a gopher sees light, it will push soil ahead and spring the trap or cover the poison.
Ground squirrels - Spenrophilus sp. of which there are 17 species may cause damage to avocado orchards by eating fruit, branches, and making burrows near or under trees which expose roots and may direct irrigation water. The most common ground squirrel is the California or Beechey ground squirrel Spermophilus beecheyi. An adult will weigh from 1 to 2 ½ pounds and is tan in color with flecked or mottled fur. Females produce one litter each year, averaging six to eight offspring. They are active in the daytime. Their diet may consist of green herbage in winter and spring and seeds during the summer and fall. They hibernate during winter. Ground squirrels are not repelled by any chemical or physical means. Thus, reductional control through the use of toxic fumigants, poison baits, traps, or shooting is the only effective control measures available. In some counties, the Agricultural Commissioner provides effective poison baits at costs. Note: The Ag Commissioner In Ventura County Does Not Provide Poison Anymore.
Opossums - The opossum, Didelphis virginiana, is nocturnal and omnivorous and will, on occasion, develop a taste for avocado fruit in orchards. This gray, long-haired, pointed-nose animal has a prehensile, rat-like tail. It is native to the eastern and south-eastern United States. It was introduced into California for hunting purposes. Opossums are easily caught in box traps, or with a number 2 leg-hold trap, either with baits or trail set in locations where damage occurs. A wide variety of baits may be used, although fish and canned pet food work well.
Source: Subtropical Fruit Pests by Walter Ebeling. U.C. Press 1959. Citrus Industry, Volume IV, U.C. Press 1978