Types of Rodents Commonly Found in California

Understanding the specific rodent you’re dealing with is the first step toward effective control. While both mice and rats are common in California, they have distinct characteristics and behaviors.

House Mice (Mus musculus)

• Appearance: These small rodents, typically brown to black with a lighter belly, are highly adaptable and frequently found both indoors and in agricultural settings.
• Size: Adults are generally 2.5 to 4 inches long, with tails of similar length.
• Droppings: Small, pellet-shaped, and roughly the size of a grain of rice.
• Behavior: Curious and exploratory, mice will often investigate new food sources or objects. They are prolific breeders, with females capable of producing 5-10 litters per year. They prefer to nest in secluded, undisturbed areas close to food sources, often within walls, attics, or behind appliances. They can squeeze through incredibly small openings, making them a common unwelcome guest in homes and businesses. House mice are known for contaminating food and surfaces with their droppings and urine.

Roof Rats (Rattus rattus)

• Appearance: Also known as black rats or ship rats, roof rats are agile climbers and often found in attics, rafters, and upper levels of structures. They are typically dark brown or black with large ears and a long, scaly tail.
• Behavior: Roof rats are agile and good climbers, preferring dense vegetation for food, nesting, and cover. Their diet is primarily fruits, nuts, seeds, and snails. They build small nests in protected places like heavy vegetation, attics, wall voids, and insulation in crawl spaces. They tend to be active in the evening, from dusk until dawn. In Lomita, their presence is often linked to fruit trees and dense vegetation, providing easy access to homes. Roof rats routinely travel up to 300 feet or more for food. They may live in the landscaping of one residence and feed on fruit trees at another residence. They can often be seen at night running along overhead utility lines or fence tops.

Norway Rats (Rattus norvegicus)

• Appearance: Larger and stockier than roof rats, Norway rats, or brown rats, are burrowing rodents usually found in basements, sewers, and ground-level areas.
• Behavior: Norway rats tend to be more urban, found in older residential and commercial areas and often associated with aging sanitary sewer systems. Norway rats live and nest in burrows. They forage at night feeding on a wide variety of foods such as meats, garbage, pet food, grains, and vegetation. They are known for gnawing through various materials, including plastic and lead pipes, to create nests and access food. Their presence in Lomita can be exacerbated by poor sanitation and readily available food waste.

Deer Mice (Peromyscus maniculatus)

• Appearance: Native to California, deer mice are typically found in wooded areas and can occasionally venture into homes, especially those bordering natural open spaces. They have distinct large ears, large eyes, and usually a bicolored tail.
• Behavior: While less common indoors than house mice or rats, they are known carriers of hantavirus, making their presence a serious health concern.

Wood Rats (Neotoma fuscipes)

• Appearance: There are at least five species of woodrats in California, including the desert woodrat, busy-tailed woodrat, white-throated woodrat, big-eared woodrat, and the most widely distributed dusky-footed woodrat.