An animal exercise wheel is illuminated by LEDs connected to a battery via a reed switch. A magnet actuates the reed switch when an animal begins to rotate the wheel. The LEDs flash with the frequency of rotation of the animal wheel or continuously. As long as the wheel rotates, the magnet continues to actuate the reed switch, which resets a counter. When the wheel stops and the reed switch is no longer actuated, the counter counts a predetermined time, and terminates the illumination of the LEDs.