Rodent Biology (Rats and Mice)

Norway Rat

The Norway rat has an average body weight of 10 to 17 oz, often well over a pound!!; The body is heavy and broad, usually between 7" and 10"; The head is long and has a blunt nose; The Norway rat tail is usually about 6 inches long, and is never as long as the body; The ears are typically small and held tightly against the body; The color is brown to black on the back and sides, and gray to yellow on the belly.
Droppings are blunt and have an average length of 3/4 of an inch

The Norway Rat prefers to feed on meats, fish, flour, fruits, vegetables...meaning it will eat almost any human consumed food!!! The Norway Rat will consume about 1 oz of food per day and about ¾ of an oz of water, and produce anywhere from 30 to 180 droppings; there are from 6 - 18 pups in a litter, and 3 – 7 liters per year; adults live about 18 months.
The Norway rat usually nests in basements & lower portions of buildings. They quite often burrow in the soil and have extensive runs. The Norway rat is active primarily at night; They are fair climbers but good swimmers; Rats are suspicious of changes in the environment or new foods, for this reason it may take a couple of days for traps or poison baits to take. Rats are nocturnal, with their peak activity at dusk or before dawn. When the population is large or they are disturbed or hungry, you can see activity during the day.

Roof Rat

The Roof Rat average body weight is 6 to 12 oz, and has a long slender body, usually 6 to 8 inches in length; the nose is pointed compared to the Norway Rat and the ears are large and very prominently displayed; The tail is long and uniform in color, and can usually reach the tip of its nose; The color is black on the back and grayish white on the underside.
Droppings are pointed and average 1/2" in length
The roof rat typically eats seed, fruits, vegetables, and grains and eggs; the roof rat will consume about an oz of food and an oz of water each day, producing 30 to 180 droppings per day; There are 6 – 14 pups in a litter, and 3 – 7 liters per year; adults live about 18 months.
Roof Rats usually enter and nest in upper portions of buildings. They can nest outside in trees, especially in palms and ivy; They rarely burrow and are excellent climbers; Very active at night; Rats are suspicious of changes in the environment or new foods, for this reason it may take a couple of days for traps or poison baits to take. Rats are nocturnal, with their peak activity at dusk or before dawn. When the population is large or they are disturbed or hungry, you can see activity during the day.

House Mouse

The house mouse weighs only 1/2 to 3/4 of an oz; Average body length is 2.5" to 3.5"; The tail is usually 3 to 4 inches in length; Ears are large and prominent; The house mouse is gray on it's back and lighter gray on it's belly;
The droppings are pointed and average 1/4" in length
The house mouse prefers meats, grains, cereals, seeds, fruits, vegetables, and will eat almost anything a human will consume; The house mouse consumes 1/10th an oz of food per a day and 1/20th an oz of water; Droppings produced are around 50 per day; There are 6 young in a litter, and 8 liters per year; adults live about 15 - 18 months;
The house mouse may nest in any portion of the building near food; They only have an average range of 50 feet from the nest; Active mostly at night; Nibbles small amounts of food instead of consuming a large meal; Very curious.