High roadkill rates in the Dong Phayayen‐Khao Yai World Heritage Site: conservation implications of a rising threat to wildlife

Abstract

Road networks are increasing globally, and as such incur increased pressure on wildlife communities. Large‐scale road expansion and infrastructure development occurring throughout Asia (i.e. Belt and Road Initiative) will affect hundreds of threatened species, leading to an increase in wildlife‐vehicle collisions. However, only a limited number of studies have quantified road mortality within this threatened landscape. To rectify this, we monitored the spatial‐temporal patterns of vertebrate roadkill in the Dong Phayayen‐Khao Yai forest complex, an UNESCO World Heritage Site located in Thailand, considered a refuge for many globally threatened species. We ran 100 standardized road surveys between 2015 and 2017, on a 47.8‐km highway transect currently being expanded, and recorded a total of 1395 casualties from 124 species. After correcting for removal time and detection probability, we estimated an average of 9688 vertebrate mortalities per year. We observed a mortality peak during the dry season for almost all taxonomic groups, due to a combination of high bird and bat mortality events. All taxa showed significant spatial clustering, highlighting high‐risk road sections. We modelled the road and landscape features most likely to lead to higher mortality rates, disentangling small‐scale (250–500 m from road) from large‐scale effects (1000–2500 m). We recorded lower mortality rates and species diversity near forest sites in protected areas, representing either lower crossing events due to habitat quality or an already depleted environment. Spatial analyses provided information on hotspots and landscape factors, which can be used to inform future mitigations at multiple scales throughout the Southeast Asia region. Our study provides a baseline of the direct road impacts on vertebrate species in a tropical biodiversity hotspot, and we suggest that more studies be conducted to fully assess the direct road effects on the many threatened species in this landscape.

Impact of highway on vertebrate roadkill in Nam Nao National Park, Thailand

“…While our study found mammals were frequently hit on HW 12 in the rainy season, albeit not significantly different from other seasons, Collinson et al (2014) and Silva et al (2019) found mammals were more likely to be hit in hot and cold seasons, respectively. We doubted the high WVC rate of mammals, mostly bats and Rodentia on HW 12 in rainy season could correlate to the time of dispersal of juveniles that happened a few months after parturition in the late hot season.…”

“…Our results explained spatial clusters of the wildlifevehicle collisions were similar to Silva et al (2019). Our results suggest two locations where mitigation measures should be implemented to reduce road mortality of amphibians, reptiles and small-and medium-sized mammals.…”

“…The mortality rate of reptiles from roadkill was the second-highest in NNNP, especially snakes, therefore, similar to Jeganathan et al (2018). Nevertheless, some other studies in Asia found that reptiles were the most vulnerable taxon among vertebrate groups (Suwanwaree and Aroon 2014;Hastings et al 2019;Silva et al 2019). The mortality rate of reptiles in NNNP was high at night and in the rainy season.…”

“…We observed only two medium-sized mammals killed on HW 12. The small number of medium-sized mammals killed on HW 12 could be due to their low density (Silva et al 2019) along HW12. Evidence from camera traps on use of drainage culvert under the bridges of HW 12 by at least seven species of medium-sized mammals could be the other reason for the low WVC of medium-sized mammals on HW12.…”

No room to roam: King Cobras reduce movement in agriculture

“…Utilisation of covered areas may also be tied to threat avoidance, as threats are known to influence animal movement [105,106]. In our study area, roads pose a major threat to many animals [107], and King Cobras routinely exit the protected area. Outside of the protected area, King Cobras fall victim to both direct [25] and indirect [108] human-caused mortality.…”