Canada lynx (Lynx canadensis)

Vertebrate scavenging can impact food web dynamics, but our understanding of this process stems predominantly from monitoring herbivore carrion and extrapolating results across carcass types. Recent evidence suggests carnivores may avoid intraguild scavenging to reduce parasite transmission. If this behavior is widespread across diverse ecosystems, estimation of nutrient cycling and community scavenging rates are likely biased to a currently unknown degree. We examined whether the time to initiate scavenging, carcass persistence, or the richness of species scavenging in the boreal forest of Yukon, Canada, differed between carnivore and herbivore carcasses. Vertebrates took longer to initiate scavenging on carnivore carcasses (3.2 d) relative to herbivore carcasses (1.1 d), and carnivore carcasses persisted on the landscape for over a month longer (48.4 d and 5.5 d, respectively). The longer persistence times were due to the reduction in scavenging by carnivores such as Canada lynx (Lynx canadensis). Decreased scavenging was caused by changes in the propensity to consume carnivore carrion, as the number of species detecting a carcass within the first week did not differ between carnivore and herbivore carcasses. These results have ramifications for our understanding of nutrient cycling and food web dynamics in the boreal forest and provide further support that carcass type should be included in future studies.

In the 1930s, the Canada Lynx (Lynx canadensis) was extirpated from Isle Royale, a 535-km2 island located in western Lake Superior, 22 km from the Ontario and Minnesota shorelines. The first half of the 20th century was a time of change on Isle Royale as Caribou (Rangifer tarandus) disappeared, Coyotes (Canis latrans) briefly appeared, moose (Alces americanus), Grey wolves (Canis lupus), and Red Foxes (Vulpes vulpes) became established, and the habitat was altered by fire, logging, and over-browsing. although these changes may have contributed to the demise of the Canada Lynx, our results suggest that over-harvest was a primary cause. assuming a peak carrying capacity of 75 Canada Lynx and harvest rates comparable to those reported from 1890–1935, a population viability analysis indicated that the island population had a 0% chance of surviving 50 years. The analysis also indicated that, even in the absence of harvest, the population had only a 14% chance of persistence for 250 years. however, when 10 Canada Lynx were added to the modeled population every 10th year, the probability of persistence increased to 100%. Our analyses suggest that the island’s Canada Lynx population maintained itself by periodic immigration across an ice bridge; therefore, natural recolonization should be possible. however, the probability of ice-bridge formation has declined from 0.8 in the winter of 1958–59 to 0.1 in 2012–13, likely as a result of climate change. The Isle Royale situation exemplifies another impact of climate change and the possible need to augment populations to mitigate the loss of connectivity.

Species across the planet are shifting their ranges in response to climate change and habitat loss. However, range shifts may vary, with populations moving in some areas but remaining stable in others; the conditions that encourage range stability rather than range shifts are poorly known. Bobcats (Lynx rufus (Schreber, 1777)) and Canada lynx (Lynx canadensis Kerr, 1792) are congeneric mesocarnivores with wide ranges across North America and range overlap in southern boreal and montane forests (the southern edge for lynx and the northern edge for bobcat). The ranges of both species are shifting in some parts of North America, in most cases resulting in a northward expansion for bobcats and a northward contraction for lynx. However, their range dynamics in the Pacific Northwest, which contains the northwestern range margin for bobcats and the southwestern range margin for lynx, have not been thoroughly documented. Here, we examine whether the range of each species has shifted in British Columbia (BC), Canada, provincially during 1983–2013 or in central BC during 1935–2013. Trapping records indicated that ranges have remained stable, and surveys from trappers supported these findings. Our findings are consistent with previous work showing that many wide-ranging species do not shift their range uniformly across their entire range edge. For bobcats and lynx, their range stability in BC contrasts with their range dynamics in other parts of North America.
Résumé
Partout sur la planète, des espèces modifient leurs aires de répartition en réponse aux changements climatiques et à la perte d’habitats. Ces modifications peuvent toutefois varier, des populations se déplaçant dans certaines régions, mais demeurant stables dans d’autres régions; les conditions qui favorisent la stabilité des aires de répartition plutôt que leur modification ne sont toutefois pas bien établies. Le lynx roux (Lynx rufus (Schreber, 1777)) et le lynx du Canada (Lynx canadensis Kerr, 1792) sont des mésocarnivores congénères dont les vastes aires de répartition à l’échelle de l’Amérique du Nord se chevauchent dans les forêts boréales et alpestres du Sud (à leurs limites sud pour le lynx du Canada et nord pour le lynx roux). Les aires de répartition des deux espèces changent dans certaines régions de l’Amérique du Nord, ce qui se traduit, dans la plupart des cas, par une expansion vers le nord pour le lynx roux et une contraction vers le nord pour le lynx du Canada. La dynamique de ces aires de répartition dans le Pacific Northwest, qui englobe la limite nord-ouest de l’aire du lynx roux et la limite sud-ouest de celle du lynx du Canada, n’a pas été documentée de manière exhaustive. Nous vérifions si l’aire de répartition de chacune des deux espèces a changé en Colombie-Britannique (Canada) à l’échelle provinciale de 1983 à 2013, et dans le centre de la province de 1935 à 2013. Les registres de piégeage indiquent que les aires de répartition sont demeurées stables, et des enquêtes auprès de trappeurs supportent ces conclusions. Nos constatations concordent avec les résultats de travaux antérieurs qui montrent que de nombreuses espèces à vaste aire de répartition ne modifient pas leurs aires de manière uniforme le long de leurs limites. Pour le lynx roux et le lynx du Canada, la stabilité des aires de répartition en Colombie-Britannique tranche avec la dynamique de ces aires dans d’autres régions de l’Amérique du Nord. [Traduit par la Rédaction]