Southern range dynamics of Canada lynx over seven decades

The range of the Canada lynx (Lynx canadensis) has contracted substantially from its historical range. Using harvest records, we found that the southern range of the lynx in Ontario in the late 1940s collapsed and then, in a short period of time, increased to its largest extent in the mid-1960s when the lynx range spread south of the boreal forest for a decade. After this expansion the southern range contracted northwards beginning in the 1970s. Most recently, there has been a slight expansion between 2010-2017. We have attributed these dynamics on the southern range periphery to the fluctuation of the boreal lynx population in the core of the species’ range. In addition, connectivity to boreal lynx populations and snow depth seemed to condition whether the lynx expanded into an area. However, we did not find any evidence to suggest that these changes were due to anthropogenic disturbances or competition. The boreal lynx population does not reach the peak abundance it once did, without which we would not expect to see large expansions of the southern lynx range as in the mid-1960s. Our results suggest that southern lynx range in Ontario have been driven by the magnitude of the boreal lynx population cycle, connectivity to the boreal forest, and snow conditions. Therefore, it is quite unlikely that southern lynx population in the Great Lakes will recover, since the warming climate and habitat changes are causing a northward contraction of the boreal forest and likely with it the core lynx populations.

Methods
We provided aggregated versions of data as they were used in our analyses. Please read through the associated publication for an in-depth explanation of how data were gathered, processed and transformed.

Furbearer harvest records and trapline information were gathered directly from the Ontario Ministry of Natural Resources and Forestry and from Novak (1987 ab).
Pelt price was gathered from Statistics Canada (http://www5.statcan.gc.ca; CANSIM Table 003-0013), Fur Institute of Canada (www.fur.ca) and from Novak (1987a and 1987b).
We adjusted the pelt price using the Consumer Price Index (CPI) for the province of Ontario also available on the Statistics Canada website (statcan.gc.ca; CANSIM Table 326-0021). 
For the distance to boreal forest we used maps supplied by Natural Resources Canada that were derived from maps from the early 1970s to the late 2000s (Brandt 2009).
Major road information was gathered from the Ontario Road Network layer (LIO; geohub.lio.gov.on.ca). 
We gathered unpublished snowshoe hare pellet data from the Ontario Ministry of Natural Resources and Forestry. We used pellet data from the longest running snowshoe hare population monitoring (since 1986) in Gogama, Ontario.
We gathered snow data from the SNOW network for Ontario wildlife database (OMNRF 2020; Warren et al. 1998).

References

Brandt, J.P., 2009. The extent of the North American boreal zone. Environmental Reviews, 17(NA), pp.101-161.
Novak, M., 1987a. Furbearer harvests in North America, 1600-1984. Ministry of Natural Resources.
Novak, M., 1987b. Wild furbearer management and conservation in North America. Ontario Ministry of Natural Resources.
Ontario Ministry of Natural Resources and Forestry (OMNRF), 2020. The SNOW network for Ontario wildlife database: 1952-2020. Ontario Ministry of Natural Resources and Forestry, Wildlife Research and Monitoring Section, Peterborough, ON. Unpublished database.
Warren, R., Bisset, A.R., Pond, B. and Voigt, D., 1998. The Snow Network for Ontario Wildlife. Ontario Ministry of Natural Resources. (Queen’s Printer for Ontario: Peterborough, ON.).