Rodents, primarily rats and mice, are a public health threat. They are known to carry diseases - most notably hantavirus. Rodents can transmit these diseases by contaminating our food supply. They can also damage structures through their gnawing or chewing. Rats can chew through wood, aluminum, cement and sheet rock. They can gnaw through plumbing pipes to gain access to water - rats must drink water on a daily basis or obtain water through their food source. Rats usually have a preference for certain foods, but are provided with numerous food sources by humans. Rats are most active shortly after sunset and before dawn. Rats and mice have vision that is adapted for nighttime. They are color blind, but can differentiate between various shades. They have hairs on their body that are attached to sensory nerves that help them to sense their environment. Hearing is well-developed enabling rodents to hear in sonic and ultrasonic ranges.