Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092201

    Quantifying forest stand and landscape attributes that influence mountain caribou habitat fragmentation and predation rates
Project lead: McLellan, Bruce (Ministry of Forests and Range)
Contributing Authors: McLellan, Bruce N.; Serrouya, Robert; Furk, Kelsey; Klafki, Richard; Poole, Kim G.; Wittmer, Heiko Uwe; Boutin, Stan
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
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 consist of young forests, it is important to know if they are impermeable to caribou and if so, what stand treatments (i.e. pruning or thinning) would encourage use. It is also important to document the attributes of young stands that are used as foraging habitat by caribou.

In 2003 we applied for 5 years of funding, the maximum allowed by FSP. Subsequently, all projects were reduced to 3 years of funding. This project is a continuation of our original proposal. Since the beginning of our FSP project in 2003, we have produced the following journal publications:

Apps, C.D. & McLellan, B.N. 2006. Factors influencing the dispersion and fragmentation of endangered mountain caribou populations. Biological Conservation, 130, 8497.
Kinley, T.A, T. Goward, B.N. McLellan & R. Serrouya. Accepted. The Influence of Variable Snowpacks on Habitat Use by Mountain Caribou. Rangifer.
Serrouya, R., B.N. McLellan, and J. Flaa. In Press. Scale-dependent microhabitat selection by threatened mountain caribou (Rangifer tarandus caribou) in cedar-hemlock forests during winter. Canadian Journal of Forest Research.
Wittmer, H.U., McLellan, B.N., Seip, D.R., Young, J.A., Kinley, T.A., Watts, G.S. & Hamilton, D. (2005a) Population dynamics of the endangered mountain ecotype of woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada. Canadian Journal of Zoology, 83, 407-418.
Wittmer, H.U., Sinclair, A.R.E. & McLellan, B.N. (2005b) The role of predation in the decline and extirpation of woodland caribou. Oecologia, 144, 257-267.
Wittmer, H.U., B.N. McLellan, & Hovey, F.W. 2006. Factors influencing variation in site fidelity of woodland caribou (Rangifer tarandus caribou) in south-eastern British Columbia. Canadian Journal of Zoology. 84:537-545.
Wittmer, McLellan, Serrouya, and Apps. Changes in landscape composition influence the decline of a threatened woodland caribou population (In Press J. Animal Ecology)
Wittmer, H.U., R.N. Ahrens, & Mclellan, B.N. Importance of inverse density dependence in PVA modelling: an example using threatened woodland caribou in British Columbia, Canada. (Submitted Biological Conservation)
Related projects:  FSP_Y081201FSP_Y103201


Final Report (0.3Mb)
Allee effects report (0.2Mb)
Moose inventory report (1.2Mb)

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Updated August 16, 2010 

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