Social interactions among Capercaillie Tetrao urogallus males outside the lek during spring

Abstract

Capercaillies have a lek-like mating system, with partly overlapping male daytime ranges extending radially out from smaller display territories at the lek. With VHF telemetry, we studied the spatial interactions among neighbouring adult males (n = 10) of different so- cial status in their overlap zones outside the lek. In addition, we recorded responses to dis- play sound that was broadcasted on the lek and in the daytime ranges. All males, irrespec- tive of social status, responded aggressively to the playback when on their display territo- ries on the lek. While in their core areas during daytime, only 2 males, known to be breed- ers, responded aggressively; others were activated, but not aggressively. When outside their daytime core areas, playbacks elicited less response among all birds. Close encoun- ters (< 300 m apart) within core areas resulted in one male leaving: beta males always left when inside alpha's core area, whereas in 4 out of 9 instances alphas left when inside beta's core areas. The results suggest that the territorial system at the lek grades into a combination of hierarchical and site-related dominance outside the lek. Daytime ranges may consist of exclusive core areas, surrounded with space shared with neighbours where subdominants avoid close spatial contact with those of higher rank. Owing to strong site fidelity and large minimum tolerance distance, the dominance hierarchical structure pro- duces a spaced-out distribution of individuals, which at lower densities gives the appear- ance of daytime territories.