How do King Cobras move across a major highway? Unintentional wildlife crossing structures may facilitate movement

Abstract

Global road networks continue to expand, and the wildlife responses to these landscape-level changes need to be understood to advise long-term management decisions. Roads have high mortality risk to snakes because snakes typically move slowly and can be intentionally targeted by drivers. We investigated how radio-tracked King Cobras (Ophiophagus hannah) traverse a major highway in northeast Thailand, and if reproductive cycles were associated with road hazards. We surveyed a 15.3km stretch of Highway 304 to determine if there were any locations where snakes, and other wildlife, could safely move across the road (e.g., culverts, bridges). We used recurse analysis to detect possible road-crossing events, and used subsets of King Cobra movement data to create dynamic Brownian Bridge Movement Models (dBBMM) in an attempt to show movement pathways association with possible unintentional crossing structures. We further used Integrated Step Selection Functions (ISSF) to assess seasonal differences in avoidance of major roads for adult King Cobras in relation to reproductive state. We discovered 32 unintentional wildlife crossing locations capable of facilitating King Cobra movement across the highway. Our dBBMMs failed to show if underpasses were being used by telemetered individuals; however, the tracking locations pre- and post-crossing provided strong evidence of underpass use. Our ISSF suggested a lower avoidance of roads during the breeding season, though the results were inconclusive. With the high volume of traffic, large size of King Cobras and a 98.8% success rate of crossing the road in our study, we strongly suspect that individuals are using the unintentional crossing structures to safely traverse the road. Further research is needed to determine the extent of wildlife underpass use at our study site and globally, alongside using previously proven fencing to facilitate their use. We propose that more consistent integration of drainage culverts and bridges could help mitigate the impacts of roads on some terrestrial wildlife, particularly in areas where roads fragment forests and wildlife corridors.

Malayan kraits (Bungarus candidus) show affinity to anthropogenic structures in a human dominated landscape

“…This may help explain the numerous documented B. candidus road mortalities in our study site (C.W. Hodges, personal observation), though we suspect culverts were used for at least some road crossings, as appears to be the case for Ophiophagus hannah 86 . Furthermore, while our ISSF models did not reveal clear evidence of avoidance of agriculture, despite agriculture being the most widespread land use type in the area, few individuals used it for shelter.…”

Malayan kraits (Bungarus candidus) show affinity to anthropogenic structures in a human dominated landscape

“…This may help explain the numerous documented B. candidus road mortalities in our study site (C.W. Hodges, personal communication, August 2021), though we suspect culverts were used for at least some road crossings, as appears to be the case for Ophiophagus hannah (Jones et al, 2021). Furthermore, while our ISSF models did not reveal clear evidence of avoidance of agriculture, despite agriculture being the most widespread land use type in the area, few individuals used it for shelter.…”