The objective of this study was to discriminate between sucking and allosucking behaviour in hinds and their calves of red deer according to the sucking duration. The duration of filial sucking was significantly longer than non-filial sucking. A large individual variance in the incidence of non-filial sucking was found. Sucking duration of occasionally allosucking non-filial calves was only marginally different from that of filial calves. Multiple sucking bouts were shorter than those with one calf. Male calves sucked longer than female calves. Frequently allosucking non-filial males sucked the longest and differently from occasionally allosucking non-filial males. Frequently allosucking non-filial females sucked the shortest and differently from filial calves of both sexes. Allosucking calves differ in their sucking behaviour and two types of allosuckers (frequent and occasional) should be taken into account when analyzing allosuckling behaviour.