The wild rats often seen in Chicago are Norway Rats (Rattus norvegicus). They are not actually Norwegian, but originated in Central Asia. In the 18th century they spread quickly across Europe, emigrated to our shores in 1775 just in time to become new Americans, and are now well established in most urban habitats in the northern U.S. and Canada. There may be as many as 235 million wild rats now living in the U.S.!

Did you know that:

• A rat will chatter or grind its teeth when it is happy.
• Rats have litters of 6-12 young, which are born 21-23 days after mating. They reach reproductive maturity in about 3 months. Breeding is most active in the spring and fall. The average female has 4-6 litters per year. With an average life span of 18 months, one pair can produce a colony of 2,000 rats in a year.
• Rats can swim a half mile in open sea and tread water for 3 days. They can dive 100 feet underwater and leap up to 4 feet!
• Rats eat the equivalent of 10% of their body weight daily, consuming rubbish, leftover dog food, bird food and dog excrement. In times of scarcity they will eat each other.
• Rats also love peanut butter, bananas, oatmeal, potatoes, meat and cooked eggs.
• Garbage-fed city rats are considerably larger than their rural cousins.
• Rats urinate as many as 80 times per day.
• Rat teeth grow 5 inches a year. Like all rodents, they must continually gnaw to wear them down.
• The white lab rat is a domesticated variety of Norway Rat.
• Rat teeth can exert 24,000 pounds per square inch. They can chew through wood, asbestos, brick, cinder blocks, four inch thick concrete, aluminum, even a 1/2-inch thick sheet of metal.
• To cool off, rats don’t pant like dogs, but instead lie on their backs and sweat through the pads on their feet.
• Rats can fit through openings that are as small as 1/2 inch in diameter, making it very difficult to rat-proof a building.
• Chicago was once home to 6 million rats. Nowadays the population is estimated at only half a million.