Integrated risk factors for vertebrate roadkill in southern Ontario

Abstract

Road mortality of animals (roadkill) threatens public safety and wildlife populations. As mitigation tools, predictive models of roadkill are becoming more common in the published literature; however, few models generalize across multiple taxa, and thus are less useful for management scenarios that account for multiple target species. Using a dataset of 653 vertebrate roadkills collected from 2 parks in southern Ontario, we constructed generalized linear mixed models to determine the simultaneous risk factors for bird, frog, mammal, five‐lined skink (Eumeces fasciatus), snake, toad, and turtle hatchling roadkills from among a set of 8 potential predictor variables. Posted road speed limit was the dominant roadkill predictor (positive coefficient), followed by maximum daily temperature (positive), habitat diversity (positive), and distance from wetlands (negative). All else being equal, as road speed limits increase from 20 km/hr to 50 km/hr, the model predicted the season's mean roadkill probability for a given location to increase from less than 0.1 to 0.75. Conversely, roadkill probability declined from 0.55 to 0.29 as distance from wetland edges increases from 0 km to 1 km. Model diagnostics calculated from randomly resampled cross‐validation datasets indicated that the best model formulation had an averaged predictive accuracy of 67.5% and an area under the curve (AUC) of 0.867. The best model also reflected seasonal patterns of animal behavior, including late‐summer frog movements and fall turtle hatching events. The best model also compared favorably to single‐taxon equivalent models. To reduce the incidence of vertebrate roadkill, we recommend that managers lower road speed limits, especially on roads near diverse habitats and near wetlands, and on warmer days if temporary signage is used. © 2012 The Wildlife Society.

European birds adjust their flight initiation distance to road speed limits

“…Species and habitat characteristics are main factors affecting this probability that also increases with bird mobility [11]. Road speed limits or surrounding landscape features can also impact the probability of being killed [12,13]. We may also expect individuals living near roads to be habituated to traffic, exhibiting potentially adaptive behaviours, for example fear responses, to limit mortality via roadways.…”

Effects of Road Density and Pattern on the Conservation of Species and Biodiversity

“…In fact, many of the research studies undertaken on road mortality tended to explore the differences between and within species with the intention of informing more targeted mitigation. For instance, studies considered in this review found that a variety of species-associated factors influenced the rate of wildlife-vehicle collisions, such as age (particularly dispersing juveniles; [19][20][21][22][23]), activity patterns (such as nocturnal and migratory activities; [6,7,24,25]), season (primarily breeding season; [12,[26][27][28][29]), gender (such as males ranging further in the breeding season in search a mate; [23,26,[30][31][32]), diet preferences (e.g., one study found that omnivorous mammals and herbivorous birds were most vulnerable; [33]), mobility (including low-flying species; [15,21,34,35]), behavioral responses (e.g., certain species do not respond to oncoming traffic; [15,36]), and home range size (i.e., the larger the home range the higher the probability of crossing a road; [37]). Another study found that species that were more inconspicuous on the roads were more vulnerable to wildlife-vehicle collisions [38].…”

“…Finally, other road characteristics that were studied included gap width [42][43][44] and traffic speed [27,43,44], both found to be positively correlation with road mortality, and road sinuosity with straighter roads leading to more wildlifevehicle collisions [32,43,45]. Transportation authorities and conservation practitioners can use these kinds of data to inform roadway design and develop targeted strategies that will reduce wildlife encounters.…”

Road Mortality of Reptiles and Other Wildlife at the Ojibway Prairie Complex and Greater Park Ecosystem in Southern Ontario

“…there are a number of reasons for this. First, most animals killed on roads are removed or obliterated within a day by scavengers, high traffic volumes, or other forces (Kline and swann 1998;Clevenger et al 2001;hels and Buchwald 2001;enge and Wood 2002;smith and Dodd 2003;DeGregorio et al 2011;santos et al 2011;Farmer and Brooks 2012), which could result in road mortality being underestimated by a factor of 12-16 (scavenging: slater 2002, as cited by DeGregorio et al 2011). second, surveying by bicycle led to slight underestimates of mortality rates of small snakes compared with surveying on foot (s. Boyle, personal communication, 2013).…”

“…efforts could be further extended to include May and august to cover additional periods of high turtle and snake mortality. Finally, the potential benefits to all vertebrate groups of permanent road closures or traffic speed reductions should not be overlooked (see Martinson 2009;Farmer and Brooks 2012).…”