Ben Maletzke helps student DJ Landes interpret the signal from a GPS (Global Positioning System) unit. The signal, from the collar worn by a female cougar, tells them where the cougar’s den is. Six times a day, the GPS transmitter sends data on the cougar’s location to a satellite. The researchers can download the data at any time. When the GPS information shows that a female cougar has stayed put for longer than a few days, it usually means she has denned up to give birth.