House Mouse

Photo of the House Mouse/Ratón Casero

House Mouse (Eng.), Ratón Casero (Sp.), Mus musculus (Sci.), introduced species.


Photo: Information compiled by Alan Mowbray, Interpretive Media Writer, EYNF/LEF

General Information

Class-Mammalia, Order-Rodentia, Family-Muridae, Subfamily-Murinae. Species-Mus musculus (Mus=mouse; musculus=musky smell). Mus musculus may have been introduced in antiquity from the Mediterranean region to China, but the species has since spread throughout the world as a by-product of trade and colonization.


The House Mouse is easily recognized: its nose-to-vent length typically ranges from 2.5 to 3.7 inches (65 to 95 millimeters), while its tail can be anywhere from 2.4 to 4.1 inches (60 to 105 millimeters) long. Its fur color is usually light brown to black, and it generally has white or buff underparts. It has a long tail with very little fur that has circular rows of scales (annulations) along its length. Its weight ranges from 0.4 to 1 ounce (12 to 30 grams).


In the wild, Mus musculus will typically occupy rock crevices or it will build an underground burrow with a complex network of tunnels comprising several chambers for nesting and storage, and multiple exits. It constructs nests from paper, leaves, or other soft materials lined with finer shreds. The House Mouse is nocturnal, foraging and mating at night, and resting during the day. It runs quickly, up to 8 miles (12 kilometers) per hour, and is an accomplished climber, jumper and swimmer. It is territorial, rarely traveling over 50 feet (15 meters) from its burrow home.

Mus musculus is an omnivore, eating seeds, fleshy roots, leaves and stems, as well as beetle larvae, caterpillars, and cockroaches. Dead meat (carrion) will also be eaten, when available. The House Mouse is a food source for a wide variety of small forest predators including feral cats, mongooses, large lizards, snakes, hawks, falcons, and owls. It avoids predation by staying concealed and also by its speed.

Mus musculus reproduces rapidly, and populations can recover quickly from predation. In the wild, the lifespan of the House Mouse is typically 12 to 18 months, maximum. Reproductive season extends from April through September; a female typically has 5 to 10 litters of 5 or 6 offspring per year. They are born naked and blind, becoming fully furred after 10 days. They open their eyes at 14 days, are weaned at 3 weeks, and reach sexual maturity at 5-7 weeks.


The House Mouse is found in the wild in forests and scrub forests throughout the island.

Where to look for this animal in the EYNF

Since Mus musculus is primarily nocturnal, it is rarely seen during the day, unless it is lured-out to scavenge food discarded by careless hikers, or from trash receptacles near nature trails in the Tabonuco section of the Forest.