Persistence of snake carcasses on roads and its effect on estimating mortality due to roadkills in a megadiverse country

Background/Question/Methods To determine the duration of fauna carcasses on roadways is important on the estimations of mortality by roadkills at regional or national levels and on visualizing the ecological impact generated by roadway infrastructure. That information, however, is lacking for most of neotropical countries. Our aim was to quantify the persistence time of snake carcasses on Colombian roads and related it with body size of the snakes and level of vehicular traffic. For this, we placed 81 snake carcasses of diverse body lengths (mean= 46.90 ± (SD) 38.46, range= 10.1–224) on 10 sampling points distributed equally on two roadways with different levels of traffic (primary road with > 2500 vehicles/day and secondary road with <1000 vehicles/day). We monitored those carcasses until their disappearance on the road surface.

Results/Conclusions The median persistence of the carcasses on roadways was of 7.16 h (5.20 h in primary roads, 14.16 h in secondary roads). The principal cause of the disappearance of carcasses was by degradation due to vehicular traffic. As the carcasses tend to increase in size, the difference in its persistence between types of roadway increased with it being lower on the primary road than on the secondary road. On the other hand, survival analysis shown that around the 75% of the carcasses disappears from the road surface after 30 h a snake has been killed. We conclude that excluding carcass persistence time from snake roadkills rate calculations decrease mortality estimates between 11.86–16.28 folds. Therefore, the problem of snakes run over on the road infrastructure of Colombia is much greater than previously considered.