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Supplemental Information: Napa County Rodents

Norway Rat Roof Rat House Mouse
Scientific Name Rattus norvegicus
Rattus rattus Mus musculus
Other Common Names Barn Rat, Brown Rat,   Common Rat, Gray Rat,   Sewer Rat, Water Rat,      Wharf Rat Black Rat, Fruit Rat,      Grey-Bellied Rat, House Rat, Ship Rat, White-Bellied Rat
Body Shape/Size Heavy, thick, large Slender, sleek Small, slender
Max. Body Wt. 18 oz. 9 oz. 1 oz.
Nose Shape Blunt Pointed Pointed
Ears Small, covered with hairs, cannot reach eyes Small, mostly without hairs. Can be pulled over eyes. Large, covered with some hair
Eyes Small Large Small
Tail Color Dark colored above, pale beneath Uniformly dark all over Uniformly dark all over
Tail Length Shorter than head and body combined Longer than head and body combined Longer than head and body combined
Droppings Rounded, blunt ends. Capsule shaped.  About 3/4″ in length. At least one end pointed, clearly tapered.  Spindle-shaped.  About 1/2″ in length. Pointed ends.  Rod-shaped. About 1/4″ in length.
Nests Mainly in burrows.  Prefers to live on the ground in holes under vegetation, edges of sidewalks, driveways and patios. Prefers to live in walls, attics, trees, climbing vines, berry vines and shrubbery against walls of houses.  Can also live in wood piles, storage boxes and yard and garden storage. Usually in or near stored materials.  Sometimes makes burrows and can be found in walls
Foraging Range Up to 300 ft. Up to 300 ft. Up to 20 ft.
Days to Maturity 60 – 90 days 90 – 120 days 30 – 35 days
Number of Young per Litter 8 – 12 6 – 10 6 – 7
Number of Litters per year 3 – 6 6 – 8 8 – 10
Food Habits Omnivorous (plants and meat), eats about 1 oz. per day.  Shy, has new object reaction. Omnivorous, but prefers more fruit, nuts, grains and vegetables.  Eats about 1 oz. per day.  Shy, has new object reaction. Prefers grains, stored dried foods.  Sometimes nibbles dried fruits, etc.
Water Needs Must find water or consume foods with a high water content on a regular basis Must find water or consume foods with a high water content on a regular basis Usually gets the water it needs from the food it consumes
Climbing Ability Can climb when necessary Active climber, very agile Good climber
Swimming Ability Excellent swimming ability Not fond of water but can swim if needed Can swim if needed
Minimal Crawl Through Opening Capable of squeezing through a space as small as 1/2″ inch in diameter. Capable of squeezing through a space as small as 1/2″ inch in diameter. Capable of squeezing through a space as small as 1/4″ inch in diameter.