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Context: Methods for estimating density of meso-carnivores in northern ecosystems are labour intensive and expensive to implement if mark–recapture and radio collaring are used. One alternative is to count tracks in the snow along transects as an index of density, but this method has been criticised as imprecise and lacking validation. Aims: We aimed to examine the utility of track counts along snowmobile trails in the snow for measuring changes in populations of Canada lynx and coyotes in the boreal forest of north-western Canada. Methods: We compared winter track counts of Canada lynx at three study sites and of coyotes at one site with concurrent estimates of density based on locations of radio-collared animals and estimates of numbers of uncollared animals from three 7–9-year studies in the Yukon and Northwest Territories, during a period of cyclical population fluctuations. Key results: Snow track counts were positively correlated (r 2 = 0.83) with density of Canada lynx, estimated by live trapping and radio collaring in the three survey areas. Coyotes also showed a clear relationship (r 2 = 0.80) between known density and snow track counts, but track counts were strongly affected by season, with much higher counts in the early winter when snow was shallower. This indicates the need to control for season or snow depth when using track counts as indices of coyote abundance. We recommend sample sizes of at least 10 track counts per winter along a 25-km transect to maximise precision. Conclusions: Snow track counts are a relatively simple, inexpensive method of concurrently tracking abundance of multiple species of meso-carnivores. These data indicate that track counts may be reliably used to monitor trends in numbers, but we suggest site-specific validation of the regressions reported here between tracks and animal abundance are required to translate these indices into estimates of density. Implications: Track counts have the potential to be an affordable alternative to more intensive methods of monitoring trends in abundance of medium-sized mammals, for purposes such as management of harvest or to measure the success of programs to increase or reduce population abundance. Estimation of abundance for cryptic species such as forest meso-carnivores is challenging. This manuscript evaluates the utility of snow-track indices for estimating abundance of Canada lynx and coyotes with data from three different intensive studies in northern Canada, and shows that track counts may be reliably used to monitor trends in numbers. We evaluate factors affecting track counts and make survey design recommendations. Photograph by Mark O'Donoghue. [ABSTRACT FROM AUTHOR]

Epigeous mushroom production in the boreal forest ecosystem varies dramatically from year to year. We tested the hypothesis that the aboveground production of epigeous mushrooms in the Kluane region, Yukon, could be predicted by summer rainfall. There is a single crop in this part of the boreal zone with maximum production during the first 2 weeks of August. We measured standing crops from 1993 to 2007 at 13 areas along 210 km of the Alaska Highway and Haines Road in the southwestern Yukon. Aboveground mushroom crops averaged 24 kg/ha wet weight but varied from 0.0 to 117 kg/ha over the 15 years of study, with a coefficient of variation among years of 143%. Epigeous mushroom production could be predicted from June rainfall of the current year and May rainfall of the year previous with [R.sup.2] = 0.85. Part of the lack of a perfect fit to rainfall was due to the constraint that years of high mushroom crops could not be followed by another high year, no matter what the rainfall pattern. We were not able to identify the species of mushrooms in this study but we confirm from natural history observations that mushrooms are a critical food for several of the small mammal species in the Yukon boreal forest. Key words: epigeous mushrooms, biomass prediction, boreal forest, Kluane Lake, Yukon, rainfall. La production de champignons epiges des ecosystemes de la foret boreale varie fortement d'une annee a l'autre. Les auteurs ont verifie l'hypothese a savoir que la production, au-dessus du sol, des champignons epiges dans la region de Kluane au Yukon, pourrait etre predite a l'aide de la precipitation estivale. Dans cette partie de la foret boreale, il y a une seule poussee avec un maximum de production au cours des deux premieres semaines d'aout. Ils ont mesure la ressource produite annuellement de 1993 a 2007 sur 13 sites etales sur 210 km de l'autoroute de l'Alaska et de la route Haines, dans le sud-ouest du Yukon. La productivite epigee en champignons atteint une moyenne de 24 kg/ha en poids frais, mais a varie de 0,0 a 117 kg/ha au cours des 15 annees de l'etude, avec un coefficient de variation au cours des annees de 143 %. On peut predire la production des champignons epiges a partir de la precipitation en juin de l'annee en cours et celle de mai de l'annee precedente avec [R.sup.2] = 0,85. On constate que les annees de fortes productions de champignons ne peuvent pas etre suivies par une autre annee de forte production, quel que soit le patron de precipitation; ceci constitue une contrainte qui empeche d'obtenir une correlation parfaite. Les auteurs n'ont pas ete en mesure d'identifier les especes de champignons dans cette etude, mais les observations de naturaliste confirment que les champignons y constituent une nourriture critique pour plusieurs des petits mammiferes qui vivent dans la foret boreale du Yukon. Mots-cles : champignons epiges, prediction de la biomasse, foret boreale, lac Kluane, Yukon, pluie. [Traduit par la Redaction], Introduction Aboveground mushroom crops in the boreal forest are known to fluctuate dramatically from year to year, and these crops are used as food both by small mammals and the [...]

Predator-prey theory predicts that in the presence of multiple types of predators using a common prey, predator facilitation may result as a consequence of contrasting prey defense mechanisms, where reducing the risk from one predator increases the risk from the other. While predator facilitation is well established in natural predator-prey systems, little attention has been paid to situations where human hunters compete with natural predators for the same prey. Here, we investigate hunting-mediated predator facilitation in a hunter-predator-prey system. We found that hunter avoidance by roe deer ( Capreolus capreolus) exposed them to increase predation risk by Eurasian lynx ( Lynx lynx). Lynx responded by increasing their activity and predation on deer, providing evidence that superadditive hunting mortality may be occurring through predator facilitation. Our results reveal a new pathway through which human hunters, in their role as top predators, may affect species interactions at lower trophic levels and thus drive ecosystem processes. [ABSTRACT FROM AUTHOR]