Abstract
Wildlife passages are currently built at roads and railway lines to re-establish connectivity. However, little is known about whether predator-prey interactions may reduce the effectiveness of the crossing structures. We evaluated the co-occurrence patterns of predator-prey species-pairs at 113 crossing structures, noting their coincidence at the same structure and/or on the same day. We built occupancy models using presence-absence matrices for three prey and five predator types obtained during 2076 passage-days of monitoring. The results indicate that predators and prey do not use passages independently. Attraction or segregation effects occurred in 20% of predator-prey species-pairs and were detected in 67% of cases with respect to same-day use. Our results show that both predator and prey species used the same structures to cross fenced roads. However, the spatial and daily patterns of crossing suggest that there were predators that attended crossings to search for prey and that prey species avoided using crossings in the presence of predators. Our results support two recommendations to avoid crossing structures losing effectiveness or becoming prey traps: (i) increase the number of wider structures to reduce the risks of predator-prey encounters and (ii) include inside them structural heterogeneity and refuges, to reduce the likelihood for predator-prey interactions.
Highlights
Road and railway constructions bring about habitat destruction and fragment the landscape into smaller and more isolated patches
We formally evaluated the existence of changes in the use of wildlife passages by predator and prey species as a response to the presence of each other
The high number of instances of significant interaction parameters stands out (Tables 2–4), and most of them point to changes larger than 10% in co-occurrence likelihood
Summary
Road and railway constructions bring about habitat destruction and fragment the landscape into smaller and more isolated patches. Division of habitats into isolated fragments has been associated with various changes in biotic interactions, including those between predators and their prey [5,6]. Wildlife passages are common measures taken to mitigate the impact of roads and railways in an attempt to reconnect landscape-scale ecological processes. They include bridges, tunnels, or adapted drainage culverts that serve to reduce roadkill and to reestablish both occasional dispersive faunal movements and regular daily or seasonal ones across the landscape [7].
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