Habitat Loss, Not Fragmentation, Drives Occurrence Patterns of Canada Lynx at the Southern Range Periphery

Abstract

Peripheral populations often experience more extreme environmental conditions than those in the centre of a species' range. Such extreme conditions include habitat loss, defined as a reduction in the amount of suitable habitat, as well as habitat fragmentation, which involves the breaking apart of habitat independent of habitat loss. The ‘threshold hypothesis’ predicts that organisms will be more affected by habitat fragmentation when the amount of habitat on the landscape is scarce (i.e., less than 30%) than when habitat is abundant, implying that habitat fragmentation may compound habitat loss through changes in patch size and configuration. Alternatively, the ‘flexibility hypothesis’ predicts that individuals may respond to increased habitat disturbance by altering their selection patterns and thereby reducing sensitivity to habitat loss and fragmentation. While the range of Canada lynx (Lynx canadensis) has contracted during recent decades, the relative importance of habitat loss and habitat fragmentation on this phenomenon is poorly understood. We used a habitat suitability model for lynx to identify suitable land cover in Ontario, and contrasted occupancy patterns across landscapes differing in cover, to test the ‘threshold hypothesis’ and ‘flexibility hypothesis’. When suitable land cover was widely available, lynx avoided areas with less than 30% habitat and were unaffected by habitat fragmentation. However, on landscapes with minimal suitable land cover, lynx occurrence was not related to either habitat loss or habitat fragmentation, indicating support for the ‘flexibility hypothesis’. We conclude that lynx are broadly affected by habitat loss, and not specifically by habitat fragmentation, although occurrence patterns are flexible and dependent on landscape condition. We suggest that lynx may alter their habitat selection patterns depending on local conditions, thereby reducing their sensitivity to anthropogenically-driven habitat alteration.

Importance of spatio–temporal connectivity to maintain species experiencing range shifts

“…A7) in Canada lynx's current range is likely to have negative implications for the species (Hoving et al 2005). Consequentially, the ARH of Canada lynx was predicted to decrease by 21-81% in 2030 from the spatial-only perspective, in agreement with other studies documenting the declining trend of available habitat for Canada lynx in this region (Hornseth et al 2014). Yet, the spatio-temporal connectivity estimation indicated that the decline in connectivity might not be so dramatic, due to the stepping-stone effects enhanced by spatio-temporal connectivity.…”

Canada lynx use of burned areas: Conservation implications of changing fire regimes

“…The finding that lynx are able to use areas of new burns offers hope to lynx in increasingly burned landscapes and corroborates a recent study that indicates lynx occupancy is affected by habitat loss but not by habitat fragmentation on a landscape scale (Hornseth et al., ). These authors suggest that in central Ontario, lynx adapted their habitat selection patterns so that fragmentation of quality lynx habitat did not affect lynx occurrence; lynx were able to adapt to local habitat conditions and use small patches of resources, thus surviving in fragmented landscapes (Hornseth et al., ). However, a tipping point must exist in burned landscapes past which the amount of useable fire residuals does not compensate for the amount of habitat lost to new, high‐intensity burned areas and lynx populations suffer.…”

Mammal responses to human footprint vary with spatial extent but not with spatial grain

“…Utilizing the additional level of data to create an index was deemed superior to losing detail by modeling presence–absence at the transect level (e.g., Hornseth et al. ). We also deemed it superior to model‐based corrections for detectability, such as in occupancy modeling (e.g., Whittington et al.…”