The California Ground Squirrel is the primary rodent pest causing damage across the state. Identified by its mottled gray-brown fur and a lighter patch around the shoulders, these animals create extensive burrow systems. These burrows undermine foundations, irrigation ditches, and paved surfaces, often leading to costly structural failures. The squirrels also pose a health threat as vectors for fleas that carry diseases, including sylvatic plague. Effective control requires a comprehensive approach that considers the animal’s behavior and California’s specific legal framework.
Understanding California Ground Squirrel Status and Regulations
The California Fish and Game Code classifies the California Ground Squirrel as a non-game mammal. Landowners or tenants may control them legally when they are actively causing damage to property or crops. This classification permits control measures not allowed for protected species, but relocation of trapped wildlife is strictly prohibited without a special permit from the California Department of Fish and Wildlife (CDFW).
A captured squirrel must be humanely euthanized on-site or immediately released back onto the property where it was caught. Landowners must properly identify the species before control, as the range of endangered species, such as the Mohave ground squirrel, may overlap. Furthermore, the use of restricted-use pesticides and fumigants is heavily regulated within the state. Many chemical control options require a Qualified Applicator License (QAL) or a Private Applicator Certificate (PAC) from the California Department of Pesticide Regulation (CDPR) for purchase and use, even for property owners.
Non-Lethal Methods for Discouraging Presence
Exclusion physically blocks access to vulnerable areas, preventing damage. To protect structures like decks or sheds from burrowing, install an underground L-shaped wire skirt. This barrier should use galvanized hardware cloth with a mesh size of one-half inch or smaller.
The wire mesh must be buried a minimum of 18 inches deep and bent outward at a 90-degree angle, extending another 12 to 18 inches to form the “L” barrier. This design prevents squirrels from digging straight down at the base of the structure. For gardens, a fence at least two feet tall with a similar buried wire apron deters climbing and burrowing access.
Habitat modification reduces the area’s attractiveness by eliminating food and cover sources. Removing brush piles, rock stacks, and accumulated debris reduces available shelter and nesting sites. Controlling irrigation to limit green, succulent growth, especially during dry seasons, also discourages squirrels from settling.
Repellents, such as predator urine or capsaicin sprays, have limited, temporary effectiveness against ground squirrels. Devices that emit high-frequency sound or vibration are generally not proven to cause a lasting reduction in established populations. Exclusion and habitat changes remain the most reliable non-lethal approaches.
Effective Trapping and Physical Removal Strategies
Trapping provides a targeted, effective means of physical removal, particularly for small to moderate infestations. Traps are categorized into live-catch traps, which capture the animal unharmed, and lethal traps, such as Conibear-style body-gripping traps. Live traps require the immediate, humane euthanasia of the captured animal on-site, as relocation is illegal in California.
Lethal snap traps, such as larger rat-sized traps, are effective near burrow entrances, especially if enclosed in a protective box to prevent capturing non-target animals. For best results, traps should be pre-baited for several days without being set, allowing squirrels to become comfortable feeding.
Kill traps, like the Conibear type, are often placed unbaited directly over the burrow entrance, sometimes using a funnel to guide the squirrel into the trap. Safety is paramount when using body-gripping traps; they must never be placed where children, pets, or protected wildlife could be inadvertently caught.
State regulations generally prohibit setting any trap within 150 yards of a permanent or temporary residence unless the trapper has written permission from the landowner. Baiting traps with attractive foods increases the likelihood of capture, including:
- Walnuts.
- Oats.
- Barley.
- Pieces of melon rind.
Chemical Control and Specialized Extermination Techniques
Chemical control methods focus on extermination within the burrow system, primarily using fumigants or restricted toxic baits. Burrow fumigants are effective when applied when soil moisture is high, such as in the spring. Moist soil helps seal the burrow system, preventing gas from escaping and ensuring a lethal concentration reaches the squirrels.
Common fumigants include gas cartridges, available to the public, which produce carbon monoxide and sulfur dioxide upon ignition. More potent options, like aluminum phosphide, generate phosphine gas and are highly restricted materials. Aluminum phosphide requires a permit and must be applied by a certified applicator.
Application of aluminum phosphide is typically limited to burrows located at least 100 feet away from human habitation due to the risk of gas leakage. Pressurized exhaust devices that pump concentrated carbon monoxide directly into the burrow are also effective and legal for use in California, often preferred by professionals as they bypass the need for an ignitable cartridge.
Toxic grain baits, particularly first-generation anticoagulants like chlorophacinone, are multiple-dose rodenticides requiring repeated feeding for a lethal dose. The use of these toxic baits is strictly regulated, often requiring a Qualified Applicator to apply them in secure bait stations. This mitigates the risk of secondary poisoning to non-target animals or predators. Always consult the local County Agricultural Commissioner for the latest regulations and permitting requirements, as misuse of restricted chemicals can result in significant legal penalties.