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How to keep rats, mice and other rodents out of your Northern California home

You’re looking through your pantry for a snack and notice a bag of chips is slightly less full than you remember it being — and there are chew marks.

You’re walking through your garage when you look down and see a dropping the size of long-grain rice.

You find shredded paper around your house and you haven’t gotten around to sorting through your mail yet, so you know it wasn’t done by you.

You’ve got rodents.

“Rodents find ways of sneaking into your home despite your best efforts,” Tracy-based AAI Pest Control says on its website.

Walking, crawling, burrowing and flying pests may seem unavoidable, but there are ways to limit their desire to come in or around your home. Here are some of the most common rodents — plus another pest — in Northern California and the Central Valley, and what you can do to help keep the undesirable ones away:

Gophers

Gophers are burrowing rodents that feed on plant roots.

“A single gopher can ruin a garden in a short time, and gopher gnawing can damage irrigation lines and sprinkler systems,” according to the University of California Statewide Integrated Pest Management Program.

The mounds they create in lawns from burrowing can interfere with playing or mowing, according to UC researchers, and detecting them early is “critical to prevent damage.”

Trapping, underground fencing and laying poultry wire or hardware cloth can help manage gopher problems and protect plants.

Rats

A rat infestation can happen quickly, before you even know you have one. Common rats in California are brown Norway rats and brown or black roof rats.

Norway rats measure up to 16 inches with their tail and live in male-dominated groups, according to AAI Pest Control. Roof rats are slightly bigger, measuring up to 18 inches. They tend to be found in the upper parts of buildings, like attics.

Rats’ gestation period is only 20 to 30 days, and they have six to 12 pups each litter, said Stephen Tahija, owner of Manteca-based Next Generation Pest Control, told in a previous interview.

“What’s even more crazy is after giving birth, they go back into heat after a few days,” Tahija said.

Rats are habitual in nature, Tahija said, and will travel only 50 feet or so from the nest. They’ll travel the same routes, gather food and take it to the nest.

Taking away rats’ water, shelter and food source will help eliminate an infestation, Tahija said, as will closing entry points into your home.

Cleaning up fallen bird seed is important to keeping rats away, Tahija said. He said fallen fruit is also an attractor, and maintaining backyard trees can help prevent both rat and bug issues.

Fixing leaky faucets, covering swimming pools and removing standing water, like in pet bowls, will help eliminate a rat’s water source.

Entry points into your home that rats will commonly use include torn crawlspace vents and, for roof rats, a crack in the soffit near gutters or an open attic window.

Rodenticides — or rat poisons — are potentially hazardous to pets and children, according to the UC pest management program. And when rats consume these products, you don’t know where they will die — which could lead to strong smells of decay if you don’t find the defeated pest.

Trapping is an effective method for controlling small numbers, although time consuming, according to the program. Trapping “permits the user to view his or her success” and snap traps can be bought at most hardware and grocery stores.

Mice

The house mouse is the most commonly encountered rodent in the country, according to AAI. It measures up to seven inches, tail and all.

The deer mouse is the most widespread and common species in California, according to the UC pest management program. They aren’t common in residential areas unless large or numerous parks or fields are nearby, and they can easily enter structures because of their small size.

The San Joaquin pocket mouse has external fur-lined cheek pouches that can be stuffed with food, according to Quail Ridge. They are generally found in grasslands.

Sealing small gaps can help prevent mice from entering homes. Mice can fit into cracks and holes as small as one-fourth of an inch.

“A good rule of thumb is that if a pencil can fit into it, a mouse could too,” Terminix states on its website.

Terminix states that garage doors can be difficult to seal completely, so tightly sealing the door that leads from the garage to the house is important to keeping mice out.

Squirrels/chipmunks

California appears to be a chipmunk hotbed, and species in the state are notoriously difficult to distinguish, according to Quail Ridge researchers.

The Sonoma chipmunk, which has been observed at the university’s 2,500-acre Quail Ridge Reserve, lives in grassland habitats and rarely is seen.

Western gray squirrels can be distinguished from California ground squirrels by their white bellies and bushier tails, according to Qual Ridge researchers. They can be seen foraging among oak or pine trees.

California ground squirrels are found in open areas such as meadows and are a significant agricultural pest in the state, according to Quail Ridge. They climb on and damage trees and vines, feed on nut, fruit and vegetable crops, and their burrows can divert irrigation water.

And according to home and lifestyle website TheSpruce.com, “Squirrels enter your home for the same reasons as mice, rats, and other rodents: They are seeking food, warm shelter, and nesting areas.”

Pigeons

Pigeons are one of the most common pests in the region. If you hear them cooing outside your window at the most inconvenient times, you already may know that.

“Pigeons are a huge problem,” Tahija said. “It’s considered a pest bird, like a nuisance bird.”

He said when California made it mandatory for new homes to have solar panels in 2020, the panels provided ideal living conditions for pigeons to nest.

“People have droppings all over their roof; there’s eggs that roll off the roof; people hear the cooing all day long,” Tahija said.

Pigeons also like large bodies of water, like the lakes that are put in to new housing developments, Tahija said.

Ultrasonic emitters, reflected light sources and repellent gels and fogging bird repellent can be used to deter pigeons, according to OvoControl, a California-based company that makes “birth control for pigeons.”

What do you want to know about life in Modesto? Ask our service journalism team your top-of-mind questions in the module below or email servicejournalists@modbee.com.