Territoriality and group sizes in Eurasian beavers (Castor fiber): echoes of settlement and reproduction?

According to current theories of territoriality, an animal is expected to defend the smallest area that can provide resources for maximisation of reproduction, known as the economically defendable area. In group territorial species however, the strategies behind resource defence are likely to be more complex with corporate territoriality, cooperative breeding, delayed dispersal and intra-group competition all potentially playing a role. Here we examined group territoriality in a social herbivorous rodent, the Eurasian beaver Castor fiber. Beavers in our study do not inhabit economically defendable territories. Instead the sequence of arrival of pairs into unoccupied areas seems to play a more important role in determining the size of the territory, whereas group size is determined by past reproductive success. We argue that the settlement pattern and reproductive history have a lasting impact in the territorial system of beavers due to a combination of the low adult mortality, high dispersal costs, and avoidance of resource depletion. [KEYWORDS: Prospective resource defence ; Resource depletion ; Territory size ; Cooperative breeding ; Delayed dispersal ; Territorial inheritance ; Habitat quality]