Road avoidance and its energetic consequences for reptiles

Abstract

Roads are one of the most widespread human‐caused habitat modifications that can increase wildlife mortality rates and alter behavior. Roads can act as barriers with variable permeability to movement and can increase distances wildlife travel to access habitats. Movement is energetically costly, and avoidance of roads could therefore impact an animal's energy budget. We tested whether reptiles avoid roads or road crossings and explored whether the energetic consequences of road avoidance decreased individual fitness. Using telemetry data from Blanding's turtles (Emydoidea blandingii; 11,658 locations of 286 turtles from 15 sites) and eastern massasaugas (Sistrurus catenatus; 1,868 locations of 49 snakes from 3 sites), we compared frequency of observed road crossings and use of road‐adjacent habitat by reptiles to expected frequencies based on simulated correlated random walks. Turtles and snakes did not avoid habitats near roads, but both species avoided road crossings. Compared with simulations, turtles made fewer crossings of paved roads with low speed limits and more crossings of paved roads with high speed limits. Snakes made fewer crossings of all road types than expected based on simulated paths. Turtles traveled longer daily distances when their home range contained roads, but the predicted energetic cost was negligible: substantially less than the cost of producing one egg. Snakes with roads in their home range did not travel further per day than snakes without roads in their home range. We found that turtles and snakes avoided crossing roads, but road avoidance is unlikely to impact fitness through energetic expenditures. Therefore, mortality from vehicle strikes remains the most significant impact of roads on reptile populations.

Survivorship and Spatial Patterns of an Urban Population of Texas Horned Lizards

“…Although this could suggest that Texas horned lizards at TAFB avoid roads, it could also be that no habitat is available north of the road because of the housing development. Road avoidance behavior has been documented in other reptile species, such as Blanding's turtles ( Emydoidea blandingii ), eastern massasaugas ( Sistrurus catenatus ) and prairie kingsnakes ( Lampropeltis calligaster calligaster ; Richardson et al 2006, Paterson et al 2019). Road mortalities at our site could have gone undetected because of the removal of carcasses by avian scavengers (Santos et al 2011, Hubbard and Chalfoun 2012).…”

Using Ecological Niche Models for Population and Range Estimates of a Threatened Snake Species (Crotalus oreganus) in Canada

“…Roadways fragment snake habitat and are also a source of mortality [64,90,91]. The warm surfaces of roads are presumably attractive to snakes for thermoregulation and so many snakes are killed by vehicles, often intentionally (N. Bertram and J. Surgenor, personal communication and [92]).…”

Identifying Potential Connectivity for an Urban Population of Rattlesnakes (Sistrurus catenatus) in a Canadian Park System

“…Each land cover class was assigned a score to reflect its relative habitat suitability for the focal species (Table A1). Land cover classes were scored from 0-100 following the method applied by Beier et al (strongly avoided [0-39], occasionally used for nonbreeding activities [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59], useable for breeding but suboptimal habitat [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79], and, best habitat for breeding and survival ) [6]. Classes were scored in units of 10 while single units were used to differentiate between classes with similar suitability but slightly different permeabilities.…”

“…Our recommendations could be used to guide interventions aimed at increasing the probability that Massasauga Critical Habitat function as an integrated unit. Although Massasaugas can incorporate high-use areas into yearly activity ranges (e.g., hiking trails [64]; roadside habitats [65]), and will use under-road crossing structures [66], conservation practitioners must explicitly address the potential negative impacts of human disturbance on connectivity (e.g., reduced movement [64], fine-scale genetic isolation [67]) to increase the likelihood of beneficial outcomes.…”