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.

The ecological and genetic mechanisms that determine Phasmatodea reproductive biology are poorly understood. The order includes standard sexual species, but also many others that display distinct types of parthenogenesis (tychoparthenogenesis, automixis, apomixis, etc.), or both systems facultatively. In a preliminary survey, we analysed Wolbachia and Spiroplasma infection in 244 individuals from 28 species and 24 genera of stick insects by bacterial 16S rRNA gene amplification. Our main aim was to determine whether some of the bacterial endosymbionts involved in distinct reproductive alterations in other arthropods, including parthenogenesis and male killing, are present in phasmids. We found no Wolbachia infection in any of the phasmid species analysed, but confirmed the presence of Spiroplasma in some sexual, mixed and asexual species. Phylogenetic analysis identified these bacterial strains as belonging to the Ixodetis clade. Other bacteria genera were also detected. The possible role of these bacteria in Phasmatodea biology is discussed.