Burrowing Rodent Management Roger A. Baldwin UC IPM Wildlife Pest Management Advisor Species Identification (Ground Squirrels) Gray-brown fur with semibushy tail. Are social. Damage includes girdling of trees, consumption of forbs and grasses, chewing of irrigation lines, and abundant burrow openings. 1
Species Identification (Ground Squirrels) Squirrels are active throughout the day and are frequently visible. They prefer to burrow next to buildings, on field edges, and alongside fencerows and roadsides. Species Identification (Pocket Gophers) Burrowing rodent about 6-8 in long; rarely seen above ground. Gopher mounds are plugged and often fanshaped. 2
Species Identification (Pocket Gophers) They feed on taproots weakening and/or killing plants. Then can girdle trees, particularly below ground. Mounds can also kill plants and can create weed seedbeds. Species Identification (Meadow Voles) Have dark grayish brown fur and are 4-6 inches in length. Populations tend to cycle, exhibiting irruptive growth patterns Voles/sq acre Vole Population Cycling 90 80 70 60 50 40 30 20 10 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 3
Species Identification (Meadow Voles) Dig shallow burrows and leave well-worn trails. Primary damage caused by girdling of stems and gnawing of irrigation pipe. Assessing Options How bad is the infestation? Is it bad enough to warrant control? 4
What time of year is it? Assessing Options What are the different costs for potential treatments? Assessing Options Are endangered species potentially present in your area? Consult your county Ag Commissioner to find out. 5
Current Control Strategies Currently, we focus on an integrated approach that utilizes a number of strategies and tools to control vertebrate pests. Importance of Biology/Ecology Understanding the biology and ecology of vertebrate pests will guide management decisions. Example: - ground squirrels 6
What Control Options are Available? Habitat modification Baiting Burrow fumigation Trapping Exclusion Repellent Frightening Shooting Pocket gopher X X X X X Ground squirrel X X X X X Meadow vole X X X Control Options Biocontrol Natural predators have been used to control vertebrate pests. Owl boxes are inconclusive at best. Gopher snakes kill a few gophers but are unlikely to control populations. 7
Control Options Habitat Modification Involves altering habitat to reduce the desirability for pests. Example: - remove brush piles to control ground squirrels. - reduce cover for voles. Control Options Exclusion Wire baskets and raised flower beds can be used to exclude gophers. Tree protectors can reduce or eliminate damage caused by voles. 8
Control Options Exclusion May be a control option to consider for voles. Plastic mesh-style fencing has been effective at slowing movement of voles into artichoke fields. Fencing should be buried at least 6 inches below ground and extend 6-10 inches above ground. Aluminum flashing may provide more long-term functionality. Must consider equipment movement into and out of fields. Control Options Trapping Control of small populations of ground squirrels and pocket gophers. Also effective at certain times of the year when other methods are less effective and can be a good follow up to alternative control methods. There are many different kinds of traps but all fall into 2 categories: - Kill traps - Live traps 9
Control Options Trapping Body-gripping traps, boxtype squeeze traps, snap traps, and pincer traps are common kill traps. Wire cage traps are common live traps. Live traps require euthanization of vertebrate pests. Control Options Trapping Ground squirrels Trapping for ground squirrels is effective year round except during middle of summer. Conibear traps can be placed at burrow entrances. 10
Control Options Trapping Ground squirrels Gopher box traps can be used in tandem when set along runways. Live traps are also effective. However, they require euthanizing captured animals. Control Options Trapping Pocket gophers Has many positive attributes including: knowledge that you ve removed the target animal. no use of toxic chemicals. available for use in organic setting. can be efficient and economical once user becomes proficient at trapping. 11
Control Options Trapping Pocket gophers Two main kinds of traps: pincers and squeeze-type box traps. Common examples include Black Box, Cinch trap, Macabee, and Gophinator. Control Options Baiting Involves use of poison baits to control vertebrate pests. There are acute and multiple-feed toxicants. Anticoagulants Zinc phosphide Strychnine Ground squirrels X X Pocket gophers X X X Voles X X 12
Control Options Baiting Anticoagulants - requires multiple feedings. - can be use for spot treatments, broadcast, or in bait stations. Control Options Baiting Zinc phosphide - is an acute toxin. - potential bait shyness. - can be used for spot treatments and broadcast baiting. - not to be used in or around buildings. 13
Control Options Baiting Pocket gophers Strychnine works best. Use probe to find tunnel. Dispense bait in tunnel. Control Options Fumigation Involves use of poison gas in burrows to control vertebrate pests. Works best when soil moisture is high (late winter early spring for gophers, after ground squirrels emerge in spring). Fumigants should not be used around buildings. 14
Control Options Fumigation Aluminum phosphide Tablets can be used for ground squirrels and gophers. Is a restricted use pesticide. Control Options Fumigation Gas cartridges Only work on ground squirrels. Caution must be used with gas cartridges to prevent fires. 15
Control Options Shooting Shooting can be effective for controlling ground squirrels although it is labor intensive. Lead bullets are no longer allowed in California Condor range. Control Options Other Strategies Gas explosive device 16
Control Options Other Strategies Carbon monoxide Questions? 17