It is hard enough getting a complete picture of how the most common animals - domestic pets, for example - behave. However, this is tougher still for creatures that are active at night, such as many species of cats, live in remote regions, or live in the top of the tree canopy. Zoologists have developed a variety of techniques to conduct behavioural studies including remote sensing, cameras and video cameras, and webcams. Part of the Animal Trackers series.