Shifter and resident red deer: intrapopulation and intersexual behavioural diversities in a predator-free area

Abstract

Context Population management of meso-large game species; knowledge of seasonal movements and sexual segregation. Aims We predicted (1) a similar mixed spatial tactic in the two sexes (shifters and residents); (2) that reproductive success could be a key factor eliciting a mixed spatial tactic in hinds; and (3) that hunting activities may affect the rutting season, influencing rutting site location. Methods We studied the spatial behaviour of 41 red deer on the Italian north-eastern Alps, from December 2003 to October 2007, by VHF radio-tracking. Key results For both sexes, two main spatial tactics were described, including residents, remaining in the same area all year long, and shifters, using non-overlapping seasonal home ranges. Most deer showed consistent spatial behaviour. In all, 87% of stags and 49% of hinds were shifters. Sexual segregation was greater in winter than in summer. All hinds wintered in the same valley, with residents in the qualitatively poorer, but protected, area. Resident hinds showed a variable yearly reproductive success, whereas usually all shifters had a calf at heel. Rutting areas of hinds overlapped with their winter or summer ranges, whereas stags occupied up to three different areas yearly. Deer distribution determined a different harvesting pressure on the two sexes. Conclusions Although shifters and residents were found in both sexes, differences in spatial behaviour of stags and hinds were consistent for seasonal occupancy, habitat selection and number of seasonal home ranges. For hinds, a mixed spatial tactic, seasonality and hunting activities could be key factors of reproductive success. Implications Hunting could affect the proportions of shifter and resident hinds at different levels, with the latter benefiting from the protection accorded. This unequally distributed selective harvesting may alter the local social structure and population dynamics in the long term. Shifter behaviour, seasonal movements and sexual segregation may bias population estimates, if counts are conducted when individuals make seasonal movements. Furthermore, the size of a hunting unit should be function of the extent of local movements of deer.