Disturbance effects of hunting activity in a willow ptarmigan Lagopus lagopus population

Hunting disturbance may affect individuals in a population by modifying their behaviour and spatial movements, which can lead to changes in home-range size and habitat use or displacement, for example into refuge areas. To evaluate effects of disturbance by recreational hunting activity, we conducted a study with 87 individually radio-marked willow ptarmigan Lagopus lagopus, in experimentally hunted and non-hunted units in central Norway during a four-year period. Contrary to a common belief among many hunters, i.e. that willow ptarmigan abandon a hunting unit in response to hunting activity, none of the birds left hunted units during the first two weeks of the hunting season in our study. Neither, did hunting affect the size of areas used by the ptarmigan or the distance between locations on consecutive days. In fact, day-to-day movements tended to be longer in non-hunted units than in hunted units. Willow ptarmigan responded to the risk of being shot by increasing their use of habitat with dense forest/scrub cover, which provided secure escape sites where birds were more difficult to locate and to shoot by hunters using pointing dogs. The increased use of cover with secure escape sites found for willow ptarmigan indicates that the catch per unit effort of hunters will vary not only with population density, but also with the amount and distribution of dense forest/shrub habitat in hunted units. Where the site-specific catch per unit effort of hunters is difficult to predict, we recommend a management scheme of harvests based on allowing a predefined number of hunters to hunt for the whole season and a seasonal bag limit per hunter.