One reason a lizard might choose the area behind or beside a bed is warmth. Reptile eggs depend on environmental heat for development. Unlike mammals, reptiles do not incubate their eggs with body heat. Instead, they rely on surrounding temperatures. Areas near walls, furniture, and mattresses often remain slightly warmer than open floor spaces. A bed can trap heat from the people sleeping on it, creating a more stable temperature nearby. To a female lizard, this may appear to be a suitable place for egg development.
Another important factor is protection from disturbance. Lizards instinctively seek hidden places where predators are unlikely to find their eggs. The narrow space between a bed frame and a wall can provide exactly that kind of shelter. It is dark, enclosed, and often difficult for larger animals to reach. Since many people rarely inspect these hidden gaps, a lizard may view them as relatively safe nesting locations.
