Examinando por Autor "Perez-Mellado, Valentin"

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Human pressure, parasitism and body condition in an insular population of a Mediterranean lizard
(Springer, 2015-04-10) Garrido, Mario; Perez-Mellado, Valentin
Many wild populations of lizards in the Mediterranean Basin inhabit small islands frequently visited by humans. Reptiles respond to humans as potential predators by escaping to refuges or by increasing antipredator behaviours which lead to a loss of body condition and may have important consequences for fitness. We assessed effects of human pressure on parasitism and body condition of the endangered insular lizard Podarcis lilfordi in Aire Island (Balearic Islands, Spain). Two areas differing in the number of visitors were compared at different seasons: spring, with almost no human pressure, and summer, when the major bulk of visitors arrive. Compared across seasons, the lizards from areas frequented by humans suffered a greater loss of body condition and showed a less parasitism reduction compared to individuals from the undisturbed area. Therefore, human disturbance seems to have deleterious effects on body condition and other fitness-related drivers, as parasitism. Results evidence important consequences of tourism for short- and long-term fitness of individuals and should be considered when designing conservation plans or management strategies
Using faecal samples in lizard dietary studies
(Brill Academic Publishers, 2011-01-01) Perez-Mellado, Valentin; Perez-Cembranos, Ana; Garrido, Mario; Luiselli, Luca; Corti, Claudia
While the use of faecal pellets is widely accepted as a primary methodological source of data for dietary studies, a recent paper advocated for the use of gut contents. This was due to the fact that faecal samples would give biased results of the diet of arthropod predators, due to a lower representation of soft-bodied prey in faecal pellets. To test this assumption, we compared the spring diet of several populations of two insular lizards from the Balearic Islands (Spain), Podarcis lilfordi and Podarcis pityusensis, using both faecal pellets and gut contents. Our results do not support the supposed bias of dietary analyses based on faecal pellets. Indeed, soft-bodied prey and particularly insect larvae are often equally represented in faecal pellets and gut contents. Alternatively, soft bodied prey are represented in different proportions in gut contents and faecal pellets, but in some cases with higher proportions being observed in the gut contents, and in other cases with higher proportions in faecal samples. We conclude that faecal pellets can be a reliable source of information for dietary studies