Resident mortality determines grey wolf range dynamics

Abstract

Large carnivores in Europe and North America are expanding their ranges, but the extent of expansion varies, with some populations showing a stable trend despite ample suitable habitat. Understanding such nuances requires dynamic modelling approaches that go beyond simple habitat association and account for interactions of resident and dispersing individuals. We investigate how such interactions influence population dynamics and range expansion of grey wolves. We developed a high-resolution Spatially Explicit Individual-Based Model (SE-IBM) for the species in the Iberian Peninsula. Here, wolves remain isolated and have not expanded over the last decades despite ample suitable habitat, thus offering a unique opportunity to study the demographic constraints to range expansion. We show that decreasing resident mortality by 10%, even when holding disperser mortality constant, increases group size (11%), reproductive success (8%) and dispersal distances (130%), and ultimately doubles the Iberian wolf distribution range in 30 years. The reduced group size and other mortality-induced group disruptions are associated with negative cascading effects on reproduction and dispersal, thereby limiting growth and expansion in wolf populations. Policy implications. In the Iberian Peninsula, enabling recovery may require effective population-level protection. More broadly, down- and de-listing policies should be supported by explicit evaluation of the indirect demographic effects under alternative management scenarios. Our detailed, process-explicit modelling framework provides a robust tool for such assessments and highlights the need to strengthen and standardize demographic monitoring to progressively refine models and support adaptive, evidence-based conservation policy.