Cyclic functional connectivity of Canada lynx (Lynx canadensis) populations across North American boreal landscapes.

Abstract

Connectivity is determined by the degree to which inhospitable habitat matrices are permeable to gene flow. Successful gene flow requires that dispersing individuals travel to new populations, survive there, and finally, reproduce. Consequently, examinations of connectivity must consider both the permeability of the landscape and individual survival patterns, as surviving individuals are the only ones that have the potential to reproduce. We investigated functional connectivity of Canada lynx (Lynx canadensis) populations in the northwestern boreal forest using an unprecedented dataset of 207,957 relocations from 142 individual lynx. As a specialist predator of snowshoe hare (Lepus americanus), lynx populations follow a 10- to 12-year population cycle, which lags a few years behind the population cycles of hares. We used integrated step selection analyses to quantify habitat selection, and Bayesian counting process implementation of wrapped Cauchy survival models to evaluate mortality risk during dispersal. We compared movement patterns and survival across behavioral states and population phases, following the a population decline. Our results showed few complete physical barriers to dispersal in the study region, with many lynx dispersing greater than 3000 km. Step-selection analysis of lynx movement revealed a higher tolerance for poor quality habitats in dispersing lynx as compared to resident lynx, primarily in selection for rugged terrain and closer proximity to roads. These differences resulted in a higher estimate of landscape permeability for dispersing lynx compared to residents. When survival patterns were considered, there were increasingly stark differences between resident and dispersing lynx during population declines. Dispersing lynx faced markedly lower survival rates than resident lynx. Overall, this paints a picture of a more connected landscape during population highs, which becomes increasingly fragmented during population lows. Canada lynx populations appeared to have few impermeable barriers across the landscape, but they face periods of low functional connectivity driven by lower survival during population declines. This emphasizes the significance of maintaining high-quality refugia habitats from which population rebounds can occur following cyclic lows.