Carnivore-mediated seed crossings are more likely on roadkill hotspots

Abstract

Roadkill hotspots concentrate animal movement and mortality, but whether they also interfere with animal-mediated seed dispersal--a conservation-relevant process underpinning plant regeneration and landscape connectivity--remains unknown. In Mediterranean oak woodlands of southern Portugal, we used seed mimics to test how road type (paved vs. unpaved) and road-forest context (edge vs. non-edge) shape carnivore-mediated seed crossings, and whether crossings coincide with roadkill hotspots detected by kernel density analysis. Bayesian logistic models indicated that seed-crossing probability was about twice as high on unpaved as on paved roads (predicted means 0.28 vs. 0.14), with weaker evidence for a negative edge effect. Crossing probability also tended to increase with carnivore abundance and distance to streams, and decrease with rodent density, albeit with some uncertainty. Crucially, paved sections intersecting roadkill hotspots showed nearly threefold higher predicted crossing probabilities than non-hotspot sections (0.51 vs. 0.18). These results yield clear conservation implications: prioritize paved segments that overlap carnivore roadkill hotspots. Implement precision measures--short-segment speed management, directional fencing that funnels animals to existing culverts/underpasses, and verge management that removes carcasses and limits small-mammal/scavenging attractants--to cut mortality while maintaining seed-mediated connectivity. A light, repeatable monitor-act-reassess workflow (hotspot mapping + seed-mimic trials + camera checks) enables rapid deployment and evaluation, and is transferable to other human-dominated forest mosaics. Hotspot-guided mitigation offers a pragmatic path to reconcile mobility infrastructure with living connectivity.