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Management of recolonising species needs precise knowledge concerning those environmental parameters that can influence the species current distribution at the margins of their range and their potential for further expansion. The otter (Lutra lutra) is one of the most endangered species of the Italian fauna. After a sharp decline, it has gradually recovered and, at present, it is confined to southern Italy. At the southern boundaries of the Italian otter range, the influence of two geographic and 15 habitat variables on otter distribution (estimated by 1-year monitoring of 18 spraint-sampling stations) was assessed, to improve management efficacy. Latitude represented the main source of variation in the spraint-collection data. The species was in fact well established in central and northern areas, whereas the southern and western sampling stations showed an unstable river occupancy (the average percentage of positive surveys being 94.5 and 35.8%, respectively; U = 0, P = 0.0014). Secondarily, otter relative abundance was positively associated with the degree of cover of aquatic macrophytes. Our results suggest that the whole analysed hydrographic network offers a suitable habitat for otters. Thus we argue that the discontinuous distribution observed in our study area could be a consequence of the sharp decline suffered by the Italian otter populations during the 1970s and 1980s. The positive trend of the last decades has resulted in the progressive recolonisation of empty habitat patches, a process that is still hindered by the lack of connectivity to extant populations. Our findings have implications for landscape restoration projects, suggesting that provision of suitable habitat alone may not be sufficient to effect recolonisation by some species.

AbstractMicroplastics (MPs) are nowadays abundant, persistent, and ubiquitous in the environment, representing a new threat for terrestrial, marine, and freshwater ecosystems. Although anuran populations and species are globally declining, the effect of MP exposure on this taxon has been poorly investigated. With the aim of assessing the effects of microplastic exposure on the defensive responses of Italian agile frog (Rana latastei) tadpoles, we exposed them to three different concentrations (1, 7, and 50 mg L−1) of a mixture of plastic polymers (HPDE, PVC, PS, and PES) for 2 weeks. Then, we measured the total distance covered by individual tadpoles before and after exposure to tadpole-fed dragonfly larvae (Aeshna cyanea) cues. As expected, predation risk sharply lowered the total distance travelled by tadpoles; however, MP concentration did not affect their defensive performances. We also collected data on tadpole development, activity, and mortality. In contrast with previous experiments, neither tadpole growth nor mortality varied with MP concentration. Our results indicate that the intensity of MP effects on growth and development may depend on tadpole size, with large tadpoles being less susceptible to the negative effects of MP exposure.