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Quantifying forest stand and landscape attributes that influence mountain caribou habitat fragmentation and predation rates
McLellan, Bruce N.
Mountain caribou are closely associated with old forests that are valuable to the forest industry. These caribou are also endangered but at the same time widely distributed. Conserving endangered animals that are old-growth dependent but live over large areas has very significant socio-economic implications. Due to these implications, mountain caribou have received considerable research attention over the past two decades. We know that mountain caribou feed almost exclusively on arboreal lichen that is most abundant on old trees and therefore these animals show strong selection for old forests during winter (Rominger & Oldemeyer 1989, Rominger et al. 1996, Terry et al. 2000, Apps et al. 2001). Considerable work has also documented how to use partial cutting silvicultural systems to maintain attributes of importance to caribou on their winter ranges (Stevenson et al. 2000). These topics were relatively easy to document because the foraging ecology of mountain caribou is not complex - they feed almost exclusively on one shrub (Paxistima myrsinites) and 2 genera of arboreal lichen (Alectoria and Bryoria) during winter (Rominger & Oldemeyer 1989, Rominger et al. 1996, Terry et al. 2000, Serrouya et al. in press). However, it is now increasingly clear that the hypothesis proposed by Bergerud and Elliot (1986) and Seip (1992) is correct and that mountain caribou populations begin to decline before there is a shortage of foraging habitat (Wittmer et al. 2005a). Predation is the proximate factor of decline (Seip 1992; Wittmer et al. 2005a,b) and the increased level of predation is linked to increasing amounts of young forests and fragmented habitat (Wittmer et al. in press, 2004). Understanding relationships among young forests, various scales of fragmentation, predation and declining caribou populations is much more complex than understanding how to maintain a food source. In addition to the implications of altering the predator/prey system by fragmenting the forest at smaller scales, fragmenting caribou populations at the broader scale is also of great concern. Telemetry studies of 358 radio-collared animals across the distribution of mountain caribou have shown that there are 18 subpopulations with no documented inter-population movement (Wittmer et al. 2005b). With 9 subpopulations consisting of < 20 animals, understanding the meta-population dynamics is also critical. Of primary importance is understanding the predator/prey system and implications of fragmenting landscapes with young, but always ageing forests. Young plantations are favourable feeding habitat for moose and deer, and increases in the number of these animals will lead to an increase in the number of wolves and cougar to where incidental kill (by-catch) may be sufficient to extirpate caribou (Seip 1992, Wittmer et al. 2005a). It has recently been suggested that it is not only the abundance of primary prey and predators but also the stability of their numbers that may influence caribou (McLellan et al. 2006). When primary prey decline rapidly, perhaps due to a weather event such as unusually deep and long-lasting snowpacks, predators may actively switch to caribou (if caribou are abundant enough) or the increased searching time of predators may result in increased incidental predation on caribou. Our goal is thus to understand a) the relationship between landscape pattern of forest harvesting and primary prey abundance, b) the age at which various plantations become more, and then less suitable for primary prey, and c) the implications of shifting predator and prey numbers on predation rates on caribou. In addition to the implications of shifts in the predator/prey system when forests are very young, densely stocked regenerating stands may also be actively avoided by caribou (Stevenson et al. 2000). If this is true, patches of old forests or partial cut forests left for caribou may not be used. Because a large proportion of the forest harvesting landbase will ...
Report Number
Executive Summary
The Influence of Forest Cover on Mule Deer... (Report)
Scale-Dependent Ecology of the Endangered Mountain Caribou... (Report)
Ecological Interactions of Mountain Caribou... (Thesis)

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