Dry riverbeds: corridors for terrestrial vertebrates

Riparian areas along rivers are essential movement corridors for terrestrial animals. However, the potential role of the dry bed of intermittent rivers as a movement corridor has been largely ignored. In this study, we investigated the use of the dry riverbed, compared with riparian, upland, and unpaved road habitats, by terrestrial vertebrates (mammals, reptiles, and birds) along two intermittent streams in Spain. Seventy-two marble dust stations were established to record the identity, number, and direction of vertebrate tracks in spring and summer. We performed generalized linear mixed models to disentangle the environmental factors affecting the frequency of occurrence (tracks per station and visit) of vertebrates. The mean frequency of occurrence was similar in both streams and included mainly small mammals, reptiles, and birds. Dry beds were widely used by vertebrates, especially along the densely vegetated Rogativa catchment. Within dry beds, directional tracks were more frequent than tracks without a recognizable direction or with changing direction; tracks that ran parallel to the riverline were particularly frequent in summer; and upward tracks predominated in one study stream in summer. Our results highlight that dry riverbeds are important movement corridors for a wide range of terrestrial vertebrates, thus enhancing natural connectivity and supporting biodiversity and ecological processes along rivers and within the entire catchment.