The evolution of leks: the point of view of female fallow deer (Dama dama)

Numerous hypothesis, not all mutually exclusive, were formulated about the selective pressures leading to the formation of leks. Mechanisms may also be variable among different species. We tested the predictions of the most discussed theories about evolution of ungulate leks, using data relative to 10 radio-collared and 92 ear-tagged females during 4 rutting periods (2000 to 2003) in the Preserve of Castelporziano, Rome. We didn’t consider models based on habitat limitation or predation risk, since we assumed them not relevant in this population. “Hotspot” model is not supported by our data: lek site was indeed not included in any of the summer home range of radio-collared females, nevertheless all of them, even if living far from lek (up to 8 km), visited the arena every year. Furthermore the frequency of tagged females seen at lek was not related to distance from capture site. In addition, during the early rut the number of bucks present at lek was 4 to 7 fold that of females, and this suggest that local female density cannot be the solely explanation for the high aggregation rate of males. If females were sucked into the lek (like a “black hole”) as a result of intense male harassment, we expected a tortuous route from the summer home range to the arena, and a straighter and faster return journey after mating: this was not the case for fallow deer females in Castelporziano. We observed that most of radio-collared females visited lek more than once, even 6-20 days before mating, when, probably, they were not in oestrus. Hence, we concluded that there is a “female preference” for clustered males. Females could gain benefits from visiting the arena, such as the opportunity to assess male quality observing them while they display and fight, or they might exploit the preference of other females to select a mate.