When Roof Rats Move Into Accounts
Used to be that roof rats (black rats) were a problem only in certain parts of the country in warmer coastal areas. They sometimes cohabit with Norway rats (brown rats) in accounts. Because the two rats have different diets, habits, and nesting sites, you can’t expect to control both using only Norway rat techniques. Consider these differences when inspecting and designing your rat control programme:
Size: Roof rats are smaller (150-250g), more slender, and usually darker in colour than Norway rats (340-453g). A roof rat’s appearance is more like that of a large mouse than a rat.
Diet: Roof rats could almost be considered vegetarians. They prefer fruits, nuts, seeds, and vegetables and are less interested in meats than Norway rats (although they love snails- a good bait choice). When food is abundant, the roof rat feeds more like a mouse, taking small meals at several locations. The Norway rat usually feeds in only one or two sites. Roof rats may be more likely than Norway rats to avoid new baits or traps.
Spatial Separation: Because the larger Norway rat usually outcompetes the roof rat for food and space, the two species may occupy different areas in the same account. Usually roof rats are on upper floors, while Norway rats occupy basement or ground level spaces (but don’t rely on this, there can be overlap). If there is an abundance of food available, both rats may coexist in the same space.
Nest Sites: Roof rats nest primarily above ground, only rarely in ground burrows like Norway rats. Their nests can be found in trees, dense vines, overgrown shrubbery, or palm trees. They also nest along riverbanks and streams, in rice or sugarcane fields, citrus groves, and in poultry houses or farm buildings. In Buildings, they can be found in attics and soffits, in false ceilings, and in other upper voids where they look for dark, protected corners for nest sites.
Habits: Roof Rats are lighter, faster and more agile than Norway rats. They are better climbers and will travel along tree branches and utility lines to enter buildings near the roof line. Roof rats leave less evidence behind in the form of droppings, urine, or tracks since they are usually travelling overhead in false ceilings or utility voids. Roof rat droppings tend to be pointed at the ends than Norway rat droppings.