Amphibian and Reptile Roadkill Incidents Along Butuan City–Las Nieves Road, Philippines, with Notes on Temporal and Spatial Mortality Distribution

Roads significantly impact biodiversity, and animal roadkill may be one of the most crucial human-caused mortality factors for some species. This study aimed to document amphibian and reptile roadkill incidents along a 25.5-kilometer stretch of the Butuan to Las Nieves Road from June 2021 to February 2022. A total of 214 carcasses were recorded from three amphibian species (n=204), namely, Kaloula pulchra, Polypedates leucomystax and Rhinella marina, and five reptilian species (n=10), namely, Dendrelaphis philippinensis, Lycodon capucinus, Naja samarensis, Coelognathus erythrurus, and Malayopython reticulatus. Amphibian Roadkill significantly threatens biodiversity, particularly native species. However, in this study, most roadkill victims were invasive alien species, and the cane toad, R. marina, exhibited the greatest mortality among species (roadkill rates= 7.76 ind./km). The high roadkill incidence of the invasive species could unintentionally aid in reducing and managing its population in the affected areas. However, since roadkills are incidental, it is not a reliable control measure. Although minimal, we recorded some endemic species impacted by vehicle collisions, which could also affect their population. The highest recorded herpetofauna roadkill incidents were in June and September (n=35). A significant difference in roadkills was recorded across sampling months (p<0.000). The acquired rainfall data indicated peak rainfall levels in November and December 2021 (284.2mm and 627.4mm, respectively). The study's results showed no significant relationship between roadkill mortality and rainfall (p-value= 0.412, r2= -0.313). The spatial pattern of roadkills was analyzed using the Kernel Density Estimation (KDE) in Quantum Geographic Information System, and three roadkill hotspots were identified. Most roadkill hotspots within the heatmap were located on road portions near forested and plantation areas and waterways. Analyzing habitat suitability and connectivity might improve the capacity to anticipate the location of roadkill hotspots. This study is the first to report on herpetofauna roadkill incidents in Butuan City and the Caraga Region.