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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]

Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9-10 year cycles throughout much of their North American range. These cycles show large variations in cyclic amplitude and we ask what factors could cause amplitude variation. We gathered data from 1976 to 2012 on hare numbers in the boreal forest of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe the amplitude of hare fluctuations and to evaluate four possible causes. First, weather could cause variation in amplitude via hare reproduction or survival, but this mechanism does not fit our data. Second, bottom-up processes involving forest succession could explain amplitude variation through changes in winter forage availability, but succession is too slow a variable in our study areas. Third, plant defenses entrained by hare over-browsing in one cycle can produce variation in plant quality and quantity in subsequent cycles. A mathematical model suggests this is a possible explanation. Fourth, predator recovery following the cyclic low is inversely related to hare cyclic amplitude, and the existing data are consistent with this mechanism. A standardized regional monitoring program is needed to improve our understanding of cyclic amplitude variation in hares and the possible role of predators and winter foods in affecting amplitude. Key words: snowshoe hare, Lepus americanus, 10 year cycle, boreal forest, predation, Canada lynx, Lynx canadensis, succession, secondary chemicals, weather. L'abondance des lievres d'Amerique (Lepus americanus Erxleben, 1777) fluctue selon des cycles de 9-10 ans dans une bonne partie de l'aire de repartition nord-americaine de l'espece. Ces cycles presentent de grandes variations d'amplitude, et nous nous penchons sur les facteurs qui pourraient causer ces variations. Nous avons recueilli des donnees de 1976 a 2012 sur le nombre de lievres dans la foret boreale de l'Alaska, du Yukon, des Territoires-du-Nord-Ouest et du nord de la Colombie-Britannique afin de decrire l'amplitude des fluctuations des lievres et d'evaluer quatre causes possibles. Premierement, si la meteo peut causer des variations d'amplitude en agissant sur la reproduction ou la survie des lievres, ce mecanisme ne concorde pas avec les donnees. Deuxiemement, des processus ascendants associes a la succession forestiere pourraient expliquer les variations d'amplitude par des variations de la disponibilite de nourriture durant l'hiver, mais la succession est une variable qui evolue trop lentement dans les zones etudiees. Troisiemement, les mecanismes de defense des plantes induits par le surbroutement des lievres durant un cycle peuvent produire des variations de la qualite et de la quantite des plantes durant les cycles subsequents. Un modele mathematique suggere qu'il s'agit d'une explication possible. Quatriemement, le retablissement de predateurs suivant le creux d'un cycle est inversement relie a l'amplitude du cycle des lievres, et les donnees concordent avec ce mecanisme. Un programme de surveillance regionale normalise est necessaire pour ameliorer la comprehension des variations de l'amplitude des cycles des lievres et de l'effet eventuel des predateurs et de la nourriture hivernale sur cette amplitude. [Traduit par la Redaction] Mots-cles : lievre d'Amerique, Lepus americanus, cycle decennal, foret boreale, predation, lynx du Canada, Lynx canadensis, succession, substances chimiques secondaires, meteo., Introduction Snowshoe hares are a classic textbook example of animals with relatively regular population cycles (Elton and Nicholson 1942; Krebs 2009, p. 203). Three key questions arise from these cycles: [...]

Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9-10 year cycles throughout much of their North American range. Regional synchrony has been assumed to be the rule for these cycles, so that hare populations in virtually all of northwestern North America have been assumed to be in phase. We gathered qualitative and quantitative data on hare numbers and fur returns of Canada lynx (Lynx canadensis Kerr, 1792) in the boreal forest regions of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe synchrony in the time window of 1970-2012. Broad-scale synchrony in lynx fur returns was strong from 1970 to about 1995 but then seemed to break down in different parts of this region. Hare populations at 20 sites in Alaska, the Yukon, and Northwest Territories showed peak populations that lagged by 1-4 years during the 1990s and 2000s cycles. The simplest hypothesis to explain these patterns of asynchrony in hare cycles is the movement of predators from British Columbia north into the Yukon and then east into the Northwest Territories and west into Alaska. A traveling wave of these cycles is clearly seen in the lynx fur returns from western Canada and Alaska from 1970 to 2009. One consequence of a failure of synchrony is that hare predators like Canada lynx and Great-horned Owls (Bubo virginianus (Gmelin, 1788)) can move from one adjacent area to the next within this region and survive long enough to prolong low densities in hare populations that have declined earlier. Key words: Lepus americanus, 10 year cycle, boreal forest, Alaska, Yukon, British Columbia, Northwest Territories, predation, climate, traveling waves. Les populations de lievres d'Amerique (Lepus americanus Erxleben, 1777) fluctuent selon un cycle de 9 a 10 ans dans une bonne partie de l'aire de repartition nord-americaine de l'espece. Il etait presume que ces cycles etaient regis par une synchronie regionale faisant en sorte que les populations de lievres de la presque totalite du nord-ouest de l'Amerique du Nord etaient en phase. Nous avons recueilli des donnees qualitatives et quantitatives sur le nombre de lievres et le nombre de peaux de lynx du Canada (Lynx canadensis Kerr, 1792) rapportees dans les regions de foret boreale de l'Alaska, du Yukon, des Territoires-du-Nord-Ouest et du nord de la Colombie-Britannique afin de decrire cette synchronie durant la periode de 1970 a 2012. Une forte synchronie regionale du nombre de peaux de lynx etait observable de 1970 a 1995 environ, mais semble s'etre estompee par la suite dans differentes parties de cette region. Les populations de lievres dans 20 localites en Alaska, au Yukon et dans les Territoires-du-Nord-Ouest montrent des maximums decales de 1 a 4 ans durant les cycles des decennies 1990 et 2000. L'hypothese la plus simple pour expliquer ces patrons d'asynchronie des cycles des lievres est le mouvement de predateurs vers le nord, de la Colombie-Britannique au Yukon, puis vers l'est, jusqu'aux Territoires-du-Nord-Ouest, et vers l'ouest, jusqu'en Alaska. Le nombre de peaux de lynx rapportees dans l'Ouest canadien et en Alaska de 1970 a 2009 temoigne clairement de l'evolution d'une onde progressive de ces cycles. Une des consequences de l'interruption de la synchronie est que les predateurs des lievres comme le lynx du Canada et le grand-duc d'Amerique (Bubo virginianus (Gmelin, 1788)) peuvent se deplacer entre differentes zones attenantes a l'interieur de cette region et survivre assez longtemps pour que perdurent les faibles densites des populations de lievres deja en baisse. Mots-cles: Lepus americanus, cycle decennal, foret boreale, Alaska, Yukon, Colombie-Britannique, Territoires-du-Nord- Ouest, predation, climat, ondes progressives., Introduction Snowshoe hares (Lepus americanus Erxleben, 1777) are a classic textbook example of animals with relatively regular population cycles (Elton and Nicholson 1942; Krebs 2009, p. 203). While much interest [...]

The abundance of Canadian lynx follows 10-year density fluctuations across the Canadian subcontinent. These cyclic fluctuations have earlier been shown to be geographically structured into three climatic regions: the Atlantic, Continental, and Pacific zones. Recent genetic evidence revealed an essentially similar spatial structuring. Introducing a new population model, the 'climate forcing of ecological and evolutionary patterns' model, we link the observed ecological and evolutionary patterns. Specifically, we demonstrate that there is greater phase synchrony within climatic zones than between them and show that external climatic forcing may act as a synchronizer. We simulated genetic drift by using data on population dynamics generated by the climate forcing of ecological and evolutionary patterns model, and we demonstrate that the observed genetic structuring can be seen as an emerging property of the spatiotemporal ecological dynamics. spatial phase synchrony | climatic forcing | phase-dependent demography | genetic diversification

Author(s): Eli Knispel Rueness [1]; Nils Chr. Stenseth (corresponding author) [1]; Mark O'Donoghue [2]; Stan Boutin [3]; Hans Ellegren [4]; Kjetill S. Jakobsen [1] The Canadian lynx, distributed all across [...]

Blurred vision is mostly due to nonpathological causes such as refractive errors and psychological trauma whereas the less frequent pathological causes include pain in the ocular surface, the iris, and the periorbital areas. Eye examination techniques and diagnostic algorithms for use by nonopthalmologists are described.