THE GOOD NEWS Remarkably, rats are also quite valuable to us, for several reasons. Rats are used extensively in the laboratory because they have a naturally short life span, they are easily tamed and can be handled by any human. Their internal organs closely parallel other higher animals, and they are large enough to be worked on easily. People are also not as sensitive to medical experimentation on rats than they would be for higher animals. For this reason, rats actually contribute their own fair share to man's development.
Black rats are much more arboreal than their cousins Norway rat.
The Norway rat , the one we have here in the Northeast, actually originated in central Asia, migrated into Europe, and is now worldwide. Rats breed all year around, with a couple of peaks. Females will defend their young ferociously, and a young rat will be sexually mature at the age of three months. A female rat will litter as many as five times a year, and can have as many as ten pups in a litter, sometimes more. That makes them quite successful.