ABSTRACT During four experiments with six female piglets, the thermoregulatory behavior of the piglets was quantified by visual observation and by automated image analysis. The collection number of images representing pigs sleeping side by side and touching each other, as well as the occupation ratio of piglets being calculated on pixel values within predefined windows, may serve as set-point values for environmental temperature controllers. But this observational procedure has to be linked to the engineering of a gradient of an effective environmental temperature within a pen.