Pest Alert – House Mice and Other Rodents

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Know Your Enemy

In general, rodents are very acrobatic. They can climb most surfaces, and make vertical jumps that are amazing for their size. Rats can leap straight up as much as 36 inches; mice as much as 12 inches.

Rats and mice are shy, but inquisitive. They initially avoid new objects, but given enough time rodents investigate every new object that shows up in their environment.

Rats and mice are nocturnal rodents, preferring to hide during the day. Mice are most active at dusk and dawn, while rats come out at dusk and head for home as the sun comes up. They don’t go full bore all night, but have multiple periods of peak activity.

Rats and mice have poor eyesight, relying on hearing, touch, and smell to navigate in their environment. These three rodents also gnaw on just about everything. It’s not a nervous habit – they must gnaw to wear down their incisors which are constantly growing. As a result, rodents damage a variety of material, including insulation, structural timbers, water lines, and wiring.

Rats and mice have an amazing reproductive potential as well. Rats breed at 3 months of age, and produce 4 to 6 litters a year with up to 12 rats each. Mice breed at 6 to 10 weeks of age, and have 5 to 10 litters a year with up 6 mice per litter. A quick bit of math makes it clear that just a few rats or mice can become many within a year or two.

House Mouse

House Mouse image from Iowa State University Extension

Primary Rodent Pests

The primary rodent pest in most situations is the common house mouse, followed by the Norway rat and the roof rat.

  • House mice are small (only 6 to 8 inches, nose to tail tip), brown to gray in color and have prominent eyes and relatively large ears.
  • Norway rats are the big ones, with adults ranging from 12 to 18 inches in length, nose to tail tip. They have fairly compact, heavy bodies, are gray to brown in color, and have relatively small eyes and ears. Their tails are generally no longer than half their body length. Roof rats are nearly as long as Norway rats at 14 to 16 inches nose to tail, but they are considerably more mouse-like in appearance. Their eyes and ears are relatively large, and their tail is as long as their entire body length.
  • The roof rat has been a relatively rare rodent in houses, but they can be a pest in farm structures. Also called the black rat, this is a relatively large rodent.


A complete rodent management program includes regular monitoring, specific sanitation practices, continuous exclusion efforts, and appropriate control for specific rodent problems.

Monitoring – Observation is your best tool in your battle against rodents. Looks for droppings, chewed items, and nests.

Sanitation – Clean areas of food waste. Move compost bins, animal feed, and any other attractant away from the home and other structures.

Exclusion – seal areas where rodents ingress and egress structures.

Control – traps and poisons are the two best control methods for rodents. Use exclusion devices to prevent accidental ingestion of rodent poison. Poison blocks or pellets should be placed in areas where rodents are present. Refresh the poison frequently. Traps and poisons can be used in tandem to maximize control.

Information excerpted from: The Essentials of Rodent Control