Ecological and behavioural variables affecting the fallow deer mating system in Doñana

Abstract

The rutting behaviour of fallow deer (Dama dama) at Doñana National Park (SW Spain) was studied in order to test the ecological and behavioural factors affecting variation in fallow deer mating strategies. Rutting area attendance was an important determinant of male reproductive success. An increase in population density during the study period did not seem to affect the variables related to the males' reproductive success, although a reduction in the size of area occupied by the males, and in the amount of their overlap between neighbours was detected. Despite this result, non-territorial strategies were perceived, and “dominance-groups” was the most successful mating strategy. In the past territorial strategies such as “rutting stands” have been described in the study area, but leks were never observed. It would appear, then, that in Doñana shifts in density do not fit the pattern which foresees that an increase in density contributes to continuous increases in territorial behaviour, reaching extremes such us multiple stands and lekking. Our study reveals that increases in density did not result in a change from non-territorial strategies. Our hypothesis is that when environmental conditions are unpredictable and/or the main mortality factors are predation and chaotic events, such as drought in the case of Doñana, environmental stress plays a more relevant role than social stress and density-dependent factors have a secondary influence on the variation in mating strategies.