Heading west: ecology of swift foxes in a novel landscape beyond their range

Abstract

The swift fox Vulpes velox is generally associated with the short-grass prairie ecosystem of the North American Great Plains; a system that has declined by approximately 50% over the last century. Yet, swift fox populations seem to demonstrate regional variation in trends, with some populations declining while others appear stable to increasing. In Wyoming, USA, swift foxes have been observed and successfully reproducing over 100 km west of their historical range boundary in shrubland-dominated habitats, previously deemed unsuitable. This has created challenges in conservation, as it is unclear what factors are uniquely important to a species occupying habitats previously considered unsuitable. Therefore, we sought to investigate fundamental questions regarding swift fox ecology in this novel habitat: 1) what environmental gradients are contributing to suitable habitat?, 2) how is swift fox habitat suitability associated with competitors (American badgers Taxidea taxus and coyotes Canis latrans) in space?, and 3) how do swift foxes and competitors allocate activity in time? Between 2021 and 2023, seven swift foxes were GPS-collared, and 71 camera traps were deployed in central Wyoming. GPS-collar locations paired with environmental covariates were used to develop a habitat suitability model using Random Forest, predicting 30.28% of our study area was suitable. Important habitat resources identified were herbaceous biomass, shrub height, and sand content. We found swift foxes likely have minimal spatial and temporal separation between competitors, specifically coyotes. We hypothesize that swift foxes may successfully coexist with competitors either by being less risk-averse for the sake of resource acquisition or by relying on abundant escape cover, which reduces the need to modulate spatial or temporal activity. Our findings enhance our understanding of environmental factors contributing to suitable habitats and how swift foxes coexist in time and space with competitors in a novel shrubland environment.