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In semi-arid environments, the effects of irregularly distributed rainfall, flow regulation and water inter-basin transfer enhance the spread of non-native fish to the detriment of native communities. In the River Segura, since the 1980s the number of non-native fish species has progressively increased, also because of the building of water transfer facility connecting the rivers Segura and Tajo. With the aim of highlighting how man-driven changes in the diversity of fish communities affect the diet of top-predators, we compared Eurasian otter Lutra lutra diet in the span of 20 years, i.e. 1997–98 vs. 2016–19. As habitat quality affects the condition of Andalusian barbel Luciobarbus sclateri, the most widespread native fish, we also compared the size of preyed barbels to point out whether human activities may have lowered their profitability to otters. Fish and introduced red swamp crayfish Procambarus clarkii formed the bulk of otter diet in both study periods. In 2016–19 the contribution of non-native species to otter diet increased significantly, both for crayfish and fish, which included ten non-native species. Otter feeding habits faithfully mirrored the variation in the composition of the fish community and confirmed the importance of crayfish as alternative-to-fish prey in the Iberian Peninsula. The average length of preyed barbels was significantly lower in the second study period, consistently with a decline in barbel profitability for otters.

A species' potential distribution can be modelled adequately only if no factor other than habitat availability affects its occurrences. Space use by stone marten Martes foina is likely to be affected by interspecific competition with the strictly related pine marten Martes martes, the latter being able to outcompete the first species in forested habitats. Hence, to point out the environmental factors which determine the distribution and density of the stone marten, a relatively understudied mesocarnivore, we applied two non-invasive survey methods, camera-trapping and faecal-DNA based genetic analysis, in an Alpine area where the pine marten was deemed to be absent (Val Grande National Park N Italy). Camera trapping was conducted from October 2014 to November 2015, using up to 27 cameras. Marten scats were searched for between July and November 2015 and, to assess density, in spring 2017. Species identification was accomplished by a PCR-RFLP method, while 17 autosomal microsatellites were used for individual identification. The stone marten occurred in all available habitats (83% of trapping sites and 73.2% of scats); nonetheless, habitat suitability, as assessed using MaxEnt, depended on four major land cover variables-rocky grasslands, rocks and debris, beech forests and chestnut forests-, martens selecting forests and avoiding open rocky areas. Sixteen individuals were identified, of which 14 related to each other, possibly forming six different groups. Using capwire estimators, density was assessed as 0.95 (0.7-1.3) ind/km(2). In the study area, the widespread stone marten selected forested areas, attaining density values like those reported for the pine marten in northern Europe and suggesting that patterns of habitat selection may depend on the relative abundance of the two competing martens

The tendency to aggregate during the larval stage is widespread and highly variable among anuranspecies. Several studies have highlighted the link between tadpole group density and their activity level,confirming that, usually, living in groups brings several antipredator benefits. However, nearly all studieshave focused on the average behavioural responses of tadpoles tested in groups. In this study, weexplored the effects of living in groups of three different sizes (1, 5 and 25 individuals per group) on theantipredator behaviour of individual green toad,Bufotes balearicus, tadpoles. Wefirst assessed their basalactivity and then examined changes in mobility rate and total distance after exposure to the chemicalcues of predatory dragonfly,Aeshna cyanea, larvae. For both the pre- and poststimulus activity levels, wealso tested the effects of the presence of conspecifics' chemical cues in the experimental tub. Our resultsshowed that (1) a previous brief (8 days) experience of group living is sufficient to affect the basal level ofactivity of individual tadpoles, which increased with group size; (2) tadpoles that were reared alone didnot lower their activity further when exposed to predators' odour; (3) the antipredator response of high-density-reared tadpoles decreased in the presence of conspecifics’cues, supporting the so-called dilutioneffect, which, anyway, may need a minimum group size to be apparent. We conclude that both previousgroup-rearing experience and current perception of the surrounding environment may affect anti-predator behaviour in individual tadpoles.