Activity patterns of urban red foxes (Vulpes vulpes) reduce the risk of traffic-induced mortality

Abstract

Traffic collisions can be a major source of mortality in wild populations, and animals may be expected to exhibit behavioral mechanisms that reduce the risk associated with crossing roads. Animals living in urban areas in particular have to negotiate very dense road networks, often with high levels of traffic flow. We examined traffic-related mortality of red foxes (Vulpes vulpes) in the city of Bristol, UK, and the extent to which roads affected fox activity by comparing real and randomly generated patterns of movement. There were significant seasonal differences in the number of traffic-related fox deaths for different age and sex classes; peaks were associated with periods when individuals were likely to be moving through unfamiliar terrain and would have had to cross major roads. Mortality rates per unit road length increased with road magnitude. The number of roads crossed by foxes and the rate at which roads were crossed per hour of activity increased after midnight when traffic flow was lower. Adults and juveniles crossed 17% and 30% fewer roads, respectively, than expected from randomly generated movement. This highly mobile species appeared to reduce the mortality risk of minor category roads by changing its activity patterns, but it remained vulnerable to the effects of larger roads with higher traffic flows during periods associated with extraterritorial movements.

Traffic Influence on Roadside Bird Abundance and Behaviour

“…Similarly, mortality of Badger Meles meles was higher on minor roads than on major roads (van Langevelde et al 2009). Behavioural adaptation found in several mammals, like change in home range, movements and diurnal activity patterns, as well as escape response to vehicle traffic, can result in reduced number of roadkills (Trombulak & Frissell 2000, Seiler & Helldin 2006, Baker et al 2007). A conceptual model showing a curved (parabolic) relationship between traffic density and number of roadkill is earlier presented based on empirical data on moose-vehicle collisions (Seiler & Helldin 2006), but as far as I know this is the first time for birds.…”

No evidence of a threshold in traffic volume affecting road-kill mortality at a large spatio-temporal scale

“…There are several hypotheses that could explain this finding: 1) a gradual decline of the species abundance in the region due to previous high mortality rates (Eberhardt et al, 2013); 2) a restriction of species movements by reducing the attempts of road crossings due to a higher perception of risk (e.g. Baker et al, 2007); and/or 3) an overall reduction in habitat quality (McClure et al, 2013) due to increasing traffic noise. Patterns of road-kills, increasing or stable over seven years, do not support the interpretation of population depletion due to road-kill (Fig.…”

“…Both the red fox and rabbit are species with clear anti-predatory behaviours, which may make them more alert to changes in traffic intensity and therefore avoid those with heavy traffic. The historical human persecution towards foxes may lead them to be cautious, reducing the rate at which they cross roads when traffic is higher (Baker et al, 2007). In an experimental study, rabbits showed that at the presence of a predator, they increase avoidance and vigilance while feeding (Monclús et al, 2005).…”

“…Hedgehogs are slow-moving and show peaks of road-kill incidence during their breeding and dispersal periods (Haigh et al, 2014). The red fox is a common carnivore with a large homerange and thus the likelihood to encounter a road is high (Baker et al, 2007). European rabbits use road verges as safe refuge from predators (Barrientos and Bolonio, 2009).…”

“…A priori, we expect that species apparently more sensitive to traffic noise like the barn owl (Hindmarch et al, 2012) and red fox (Baker et al, 2007) will show a lower road-kill probability in highway segments with heavy traffic. In contrast, we expect a positive and linear relationship between traffic and mortality for the hedgehog and rabbit, which are apparently less sensitive to traffic because they are often found on highway verges (Doncaster et al, 2001;Barrientos and Bolonio, 2009).…”