PDF《wolf》

24 h (Fischhoff et al. 2007). In general, the presence of lions within a 2-km ?xed radius during the previous

24 h in?uences habitat prefer- ences of both grazers and browsers (Valeix et al. 2009). Most of these ?ne-scale studies (i) approximate perception of predator presence by a binary presence/absence of predator (ii) in a ?xed radius and (iii) over a ?xed tempo- ral window around the prey locations. This coarse level of information on prey'

s assessment of predator presence might not suf?ce to evaluate the role of anti-predator behaviours on the spatial dynamics of prey and, more generally, on food web properties. Here, we evaluated the behavioural response of forest- dwelling woodland caribou (Rangifer tarandus caribou L.) and moose (Alces alces L.) to the passage of grey wolves, in the C?te-Nord region of Québec during winter and summer. Forest-dwelling caribou is considered threatened across the Canadian boreal forest (COSEWIC 2006), and the conservation of this ecotype has a strong impact on forest management. Food resources are not considered as a limiting factor for these caribou, and, instead, their pop- ulation dynamics would be driven by top-down forces (Courtois et al. 2007). Given the importance of risk effects on top-down systems, a better understanding of the perception of predator presence by caribou, and their reaction to it, can provide valuable information of high conservation value. The response of moose to predation risk can also have consequences on caribou conservation, because a high hunting success of wolves on moose can lead to an increase in the wolf population, which in turn can be detrimental to the caribou populations (Wittmer et al. 2007). We assessed nonlethal effects of wolves on caribou and moose by means of using step selection functions (SSF, Fortin et al. 2005) integrating information on both animal movements and habitat selection, along with an index of predator presence. This indexes a discounting function of both time since and distance from passage. The discounting function was assessed using optimization techniques applied to the SSFs, which identify the tem- poral scales and spatial extents over which caribou and moose respond to the recent passage of wolves in sum- mer and winter. Our results highlight the dynamic aspect of the predatorCprey game, which characterized by a combination of chronic and ephemeral anti-predator responses. ?

2013 The Authors. Journal of Animal Ecology ?

2013 British Ecological Society, Journal of Animal Ecology, 83, 185C198

186 G. Latombe et al. Materials ........