Adaptedness of Arena Behaviour in Black Grouse (Tetrao Tetrix) and Other Grouse Species (Tetraoninae)

Abstract

AbstractI. Arena grouse species probably descended from a forest-living grouse species. 2. The behaviour of arena grouse species differs from the behaviour of forest-living grouse species with respect to the size of individual home ranges, the type of territory which is defended by males and the gregariousness of males as well as females. These differences indicate in which aspects the behaviour of arena grouse species is adapted to their present environments. 3. The large individual home ranges in arena grouse species are in all likelihood an adaptation to environments in which critical ecological resources are unevenly distributed. 4. The defence of small territories on arenas by males of arena grouse species can be explained as an adaptation which enables territorial males to exploit large home ranges and to live in groups continuously. 5. Several advantages may be cormected with group life in arena grouse species. There is some evidence that groups provide possibilities to acquire information about the location of resources. Groups may provide protection against conspecific territorial males which control the population distribution range outside arenas. It cannot be excluded that groups also provide protection against predators. 6. Female mating preferences in arena grouse species for males in a cluster probably evolved because clustering has ecological advantages for males. 7. Female mating preferences for clustered males may have resulted in a "runaway process" through which the tendency to cluster in males became stronger than is most advantageous with respect to their chances of staying alive.