Did you find a mouse or a rat in California?
First, I hope it was outside and NOT in your house. 🙂
Second, I’m guessing you’re here to try and identify the correct species. Luckily, you’ve come to the right place! I’ve compiled a list of the most common mice and rats that live in California, with photos and range maps to help find the one you’re looking at.
Unfortunately, mice and rats can be hard to identify. First, many species look similar to each other. In addition, due to their shy nature and small size, it can be hard to get a good look. You may want to consider purchasing the book below if you need additional help with rodent identification.
Here are 13 COMMON Mice and Rats Found in California!
#1. Brown Rat
- Rattus norvegicus
The Brown Rat is among the most widespread rats in California!
It goes by many names, including the common rat, street rat, and sewer rat. You may also know it as the gray rat or Norway rat.
Interestingly, the Brown Rat isn’t native to North America. Instead, it’s thought to have originated in China and Mongolia.
Look for Brown Rats anywhere people are living, particularly in urban environments. They’re best known for living in sewer tunnels and subway systems, scavenging food from the trash.
Although many people find rats off-putting, others keep a sub-species of Brown Rats as pets. This subspecies, called the Fancy Rat, was bred specifically for the pet trade. Besides companion animals, rats can be trained for many jobs to assist humans, like detecting gunpowder for forensic teams and providing therapy support.
It’s a misconception that Brown Rats spread bubonic plague. In actuality, it’s more commonly spread through ground squirrels! Regardless, Unfortunately, they can still transmit infections of many kinds though as their blood can carry several diseases,
#2. Black Rat
- Rattus rattus
The Black Rat is a naturalized species in North America. It’s thought to be native to India but was transported here on cargo ships and has become so widespread that it’s no longer considered a foreign species.
It’s considered a pest in the agricultural market because it feeds on a wide variety of crops. Like other rodents, Black Rats can carry pathogens in their bodies. While they may not appear sick, they can spread infections like toxoplasmosis, typhus, and bubonic plague.
In many areas where the Black Rat was once the dominant species, the Brown Rat has taken over. Black Rats are slightly smaller and reproduce less often, which are two of the reasons this species isn’t as widespread as Brown Rats.
Black Rats go by many common names, such as ship rat, roof rat, and house rat.
#3. House Mouse
- Mus musculus
Most mice in California can live around people, but few thrive as well as the House Mouse!
If you picture a small, mischievous cartoon mouse when you think of mice, then you’re probably familiar with this species! House Mice have the characteristic large ears, thin tails, and tiny bodies of a typical “mouse.” They do incredibly well in highly populated areas, and there are now more semi-tame populations than wild. These populations live near people and depend on them for food and shelter.
House mice are the most common species to find inside your home because they’re so adaptable to human presence. They readily eat food scraps, build their nests in walls or dark attics and basements, and spend most of their time hidden from view. In fact, you’ve likely shared your home with a House Mouse at least once over the years. Although most people would prefer not to have them, they aren’t the worst roommates!
Like their eating habits, they are adaptable in their social behavior. Populations of House Mice that have an excess of food, like those that live in buildings, form a hierarchy with leaders and followers. However, in the wild, where food is less plentiful, females aggressively protect their territory from one another.
#4. White-throated Woodrat
- Neotoma albigula
Look for White-throated Woodrats in deserts and pine forests, where they make nests of plant material and branches. Underneath their nests, they construct shallow tunnels with “rooms” to store food. They’re particularly fond of shiny objects like CDs and tin foil, often adding shiny trash to their nesting site.
Like other rats in California, their large ears help them hear and provide a natural way to regulate heat during warm weather.
The typical diet of the White-throated Woodrat is mostly prickly pear cactus, but they eat a variety of leaves, stems, and fruit from other plants. They don’t generally have to drink water because they get the hydration they need from their food.
#5. Desert Woodrat
- Neotoma lepida
The easiest way to identify the Desert Woodrat is to look at its feet! Although their coloring is highly variable, their feet and undersides are always white.
Like many rats in California, this species is a food source generalist and will consume any type of plant matter available. This is handy for the Desert Woodrat, whose habitat often has long droughts.
During especially dry weather, Desert Woodrats become territorial over water sources and will prevent other species from accessing succulent plants or cacti in their territory.
#6. Bushy-tailed Woodrat
- Neotoma cinerea
Though not as furry as a squirrel’s, the tail of this woodrat is quite bushy. So it’s easy to see how the Bushy-tailed Woodrat got its name!
This species is the original “pack rat,” a term that describes its fondness for shiny objects. They’ll often drop food or nesting material in favor of coins, shiny metal, or foil! Look for Bushy-tailed Woodrats in forests, shrubland, and grasslands with boreal and temperate climates. They’re excellent climbers and often spend time in trees, clinging to the bark with their sharp claws.
Like many rats in California, these rodents use their strong tails for balance to aid in jumping and climbing.
#7. Cactus Mouse
- Peromyscus eremicus
Look for Cactus Mice in deserts and dry mountain foothills. Their diet changes throughout the year as different food sources become available. For example, in the spring, they mainly eat grasses and the flowering portions of plants, but they transition to a winter diet of mostly insects.
Although they’re shy and excitable when handled, they rarely bite. Because of their docile nature and clean living environment, they are often used as laboratory specimens.
Interestingly, this species will enter a state of torpor, or dormancy, if they cannot find adequate food. Some laboratory studies found they would enter torpor in as little as 30 minutes if deprived of food.
#8. Canyon Mouse
- Peromyscus crinitus
Canyon Mice are mostly nocturnal and active throughout the year.
They eat seeds, insects, and vegetation like grasses and leaves. They prefer a dry climate but can be found in many different habitats, from deserts below sea level to mountain forests.
This species is solitary except during the mating season, and females are particularly territorial once they give birth to their young. Therefore, mating pairs do not stay together once the female conceives.
#9. Eastern Deer Mouse
- Peromyscus maniculatus
Eastern Deer Mice are one of the most widespread mice in California.
Its various subspecies are spread all over the country. To identify, look for a small gray or brown mouse with large black eyes, round ears, and white feet.
They can reproduce throughout the year, although they typically only do so in the warmer parts of their range.
Although we generally think of mice as ground creatures, Eastern Deer Mice prefer to nest high up in hollow trees. Their sharp claws allow them to climb to incredible heights!
In addition to spending time in forests, this species is also commonly found in houses! They feed on food scraps and crumbs and make nests in small spaces. Because they’re so numerous and widespread, they’re incredibly hard to get rid of if you have an infestation.
#10. Brush Mouse
- Peromyscus boylii
The Brush Mouse’s name is fitting for two reasons. First, its preferred habitat is brushy, forested areas with plenty of hiding places. Second, its tail is hairless except for the tuft at the end, which looks like a paintbrush.
Brush Mice are nocturnal, like most mice in California.
They spend their days in nests under rocks, fallen logs, or in trees. Interestingly, where individual Brush Mice spend their time seems determined by their tail length. Longer-tailed individuals spend more time climbing than shorter-tailed mice.
They primarily eat acorns but supplement their diet with insects, berries, and leaves. Foxes, birds of prey, and large rodents are their main predators.
#11. Pinyon Mouse
- Peromyscus truei
Compared to other mice in California, the Pinyon Mouse’s ears are enormous for its body!
This species is flexible when it comes to habitat, ranging from grasslands to mountain forests and even the desert. However, you will most likely see the Pinyon Mouse on rocky slopes.
Because of their varied habitats, Pinyon Mice have to be adaptable to many different climates. They adjust their food intake based on how much water is available in their area.
For instance, in a desert environment, they will eat more leafy plants and cactus parts for the water content, but in a forested area with regular rainfall, they may eat more seeds and insects.
#12. Western Harvest Mouse
- Reithrodontomys megalotis
This nocturnal species is most active on particularly dark nights. Your best chance to see one would be during the new moon after dusk.
Unlike other mice in California, the Western Harvest Mouse is a strict herbivore and does not typically consume insects. Instead, it feeds primarily on fruit, grasses, and seeds.
Western Harvest Mice will occasionally eat grasshoppers and caterpillars if these food sources become scarce. They nest on the ground and spend most of their time there, only rarely venturing into shrubs or low trees in search of food.
#13. Northern Grasshopper Mouse
- Onychomys leucogaster
Unlike other mice in California, the Northern Grasshopper Mouse is carnivorous.
Remarkably, its diet is made up primarily of insects, smaller mice, and even snakes. That’s one tough little rodent!
They create multiple burrows in their territory for different purposes. First, the nest burrow is used for sleeping during the day. The second type of burrow, a cache burrow, is used as a pantry to store excess food. Finally, escape burrows provide a way to quickly avoid predators. These are the deepest burrows, about ten inches deep and angled 45 degrees to keep predators out.
Do you want to learn about other MAMMALS in California? Check out this field guide!
- 20 COMMON Mammals in California! (ID Guide)
Which of these mice and rats have you seen before in California?
Tell us below in the COMMENTS section!