Climate change is the primary driver of white‐tailed deer (Odocoileus virginianus) range expansion at the northern extent of its range; land use is secondary

Abstract

Quantifying the relative influence of multiple mechanisms driving recent range expansion of non‐native species is essential for predicting future changes and for informing adaptation and management plans to protect native species. White‐tailed deer (Odocoileus virginianus) have been expanding their range into the North American boreal forest over the last half of the 20th century. This has already altered predator–prey dynamics in Alberta, Canada, where the distribution likely reaches the northern extent of its continuous range. Although current white‐tailed deer distribution is explained by both climate and human land use, the influence each factor had on the observed range expansion would depend on the spatial and temporal pattern of these changes. Our objective was to quantify the relative importance of land use and climate change as drivers of white‐tailed deer range expansion and to predict decadal changes in white‐tailed deer distribution in northern Alberta for the first half of the 21st century. An existing species distribution model was used to predict past decadal distributions of white‐tailed deer which were validated using independent data. The effects of climate and land use change were isolated by comparing predictions under theoretical “no‐change between decades” scenarios, for each factor, to predictions under observed climate and land use change. Climate changes led to more than 88%, by area, of the increases in probability of white‐tailed deer presence across all decades. The distribution is predicted to extend 100 km further north across the northeastern Alberta boreal forest as climate continues to change over the first half of the 21st century.

Human disturbance alters the predation rate of moose in the Athabasca oil sands

“…We excluded any models containing covariates with a correlation coefficient >0.7. Latitude was included in the species model selection because deer densities are expected to decrease with latitude (Dawe and Boutin 2016). For both the kill and species models, we selected the most parsimonious model within 2 delta Akaike's information criterion (AIC c ) of the top ranking model.…”

Observed and predicted effects of climate change on Arctic caribou and reindeer

“…Although the distributional changes of Rangifer populations can have demographic effects, these populations also might be affected by the range expansions of other species. The northern expansion of ungulate species, such as moose (Alces alces) (Norment et al 1999) and white-tailed deer (Odocoileus virginianus) (Veitch 2001;Dawe and Boutin 2016) could increase interspecific competition for certain forage species and introduce novel pathogens to Rangifer populations (Kutz et al 2009). For example, increases in productivity on the tundra and more frequent wildfire activity (which increases the proportion of immature to mature forests) on migratory caribou winter ranges (see section below) is predicted to improve habitat quality for moose and resultantly increase their abundance on caribou ranges (Sharma et al 2009;Joly et al 2012).…”

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

“…Range expansion along upper limits was especially evident when a negative abiotic factor decreased along with a corresponding increase in positive unlinked biotic factors (Dawe & Boutin, ; Lavoie et al, ). Some of the best examples include the northward expansion of opossum Didelphis virginiana and raccoons Procyon lotor in response to increasing food availability in conjunction with warming climate (Kanda, Fuller, Sievert, & Kellogg, ; Larivière, ; Pitt et al, ).…”