Contrasting wolf responses to different paved roads and traffic volume levels

Emma Dennehy,Luis Llaneza,José Vicente López-Bao

doi:10.1007/s10531-021-02239-y

Abstract

In some regions of the world, large carnivores, such as wolves, persist in landscapes with dense networks of paved roads. However, beyond the general impacts of roads on wildlife, we still lack information on carnivore responses to different types of roads and traffic volume levels. Using wolves in NW Spain as a case study, we show how wolves respond differently to paved road classes depending on road size, speed limit and traffic volume. All wolves evaluated (25 GPS collared wolves) crossed paved roads. Overall, during 3,915 sampling days, we recorded 29,859 wolf crossings. Wolf crossings of all paved road classes were recorded at a mean rate of 0.022 crossings/day/km (95% CI 0.016–0.027). Wolves crossed low speed and low traffic volume roads more frequently, and more often during the night, in order to lessen the chances of encountering traffic. We found mortality to be highest on roads with high speed and high traffic volume. How wolves interact with paved roads should be considered in landscape planning strategies in order to guarantee wolf long-term persistence in human-dominated landscapes. In our case, our results support an increasing focus on primary roads (class II) to identify segments of these roads where road mitigation efforts should be prioritised. Our study also highlights the importance of considering paved road classes when studying the impact of roads on wildlife.

Highlights

The magnitude and rate of change in land-use cover presents a challenge in endeavouring to fully understand the responses of wildlife to ever-encroaching human environments (Torres et al 2016; Watson et al 2016)
Wolf crosses of all paved road classes were recorded at a mean rate of 0.022 crossings/day/km
The most parsimonious model explaining the variation in wolf crossings over paved roads was the model considering road class, time period and their interaction

Summary

Introduction

The magnitude and rate of change in land-use cover presents a challenge in endeavouring to fully understand the responses of wildlife to ever-encroaching human environments (Torres et al 2016; Watson et al 2016). The expansion of roads in human-dominated landscapes can exacerbate habitat loss and fragmentation, lead to direct mortality by vehicle collisions and increase disturbance and human pressures on wildlife (e.g., Mech et al 1988; Fahrig et al 1995; Saunders et al 2002; van Langevelde and Jaarsma 2004; Shephard et al 2008; Ceia-Hasse et al 2017; Laurance et al 2017). The impact of linear infrastructures on large carnivores, and their behavioural responses, has been the focus of attention in recent times (e.g., Whittington 2005; Llaneza et al 2012; Basille et al 2013; Dellinger et al 2013; Boulanger and Stenhouse 2014; Ordiz et al 2014; Riley et al 2014; Ceia-Hasse et al 2017; Find’o 2019; López-Bao et al 2019; Zeller et al 2021; Proctor et al 2019). Studies have shown how carnivores can perceive risks of crossing roads, with black bears (Ursus americanus) having elevated heart rates when crossing high-traffic volume roads (Ditmer et al 2018) or higher movement speeds when crossing roads than during other situations (Zeller et al 2021), and grizzly bears (Ursus arctos horribilis) increasing their selection of roads closed to traffic (Whittington et al 2019)

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