The three main rodent pests in the Lower Mainland are the house mouse, Norway rat and the black or roof rat. They can carry disease, transport parasites, and chew through wires and pipes causing fires, power shortages, or flooding. These three rodents are primarily nocturnal but will be seen during daylight hours if the population is disturbed, under stress, or very large.
Norway rat (Rattus norvegicus)
The Norway rat is the largest of the three primary rodent species in the Lower Mainland, weighing about 600g. Their droppings (feces) are approximately 2cm in length with blunt ends. They have 3 to 6 litters per year with 8 to 12 young per litter. Norway rats tend to have a large territory and will travel up to 150 feet from their nesting area to a food or water source. They prefer moist conditions and often nest in the lower portions of buildings or in burrows outside.
Black or roof rat (Rattus rattus)
The black or roof rat is much smaller than the Norway rat, weighing up to 400g. Their feces are about 1cm long and have pointed ends. They have 4 to 6 litters per year with 6 to 8 young per year. These rats are excellent climbers and often nest in attics but will also nest in crawlspaces or burrows. Roof rats only require an opening of about 1.5cm in diameter to enter a building and can enter from either ground level or the roof, sometimes using overhead utility lines or trees. Both the Norway rat and the roof rat are neophobic; that is, they fear new objects. While rats will investigate their territories daily, they will often shy away from new objects, including bait or traps, for many days.
House mouse (Mus musculus)
A house mouse is a small rodent weighing 20 to 25g, and is usually 6 to 9cm in length. Mouse droppings are quite small, 2.5 to 5mm with smooth ends. They have up to 8 litters per year with an average number of 6 per litter. Mice prefer to nest in dark, secluded areas within 30 feet of their food source. A mouse can enter a structure through an opening of only 4 to 6mm in diameter. Mice will travel through their territory daily, but unlike rats, they like to explore new things in their environment.