Efecte de l’estructura de l’hàbitat en la demografia i morfologia de la tortuga d’estany (Emys orbicularis)

Abstract

The European pond turtle (Emys orbicularis) has a wide global distribution, but usually it's

found in small and fragmented populations. In Spain, it is classified as vulnerable, with

populations in the northwest and Levant regions considered to be in danger. The main

threats are habitat destruction and fragmentation due to agriculture and urbanization, as well

as climate change and invasive species. In Catalonia, captive breeding and habitat

restoration programs have been ongoing since 1980, particularly in the province of Girona

and Tarragona.

To carry out habitat-focused species management, it is essential to understand its

environmental preferences. The main objective of this study was to analyse the effect of

habitat structure on demography and morphology of the species. Environmental effects have

been studied at both microscale and mesoscale levels, on the demography of the species,

inferring on the abundance, sex ratio and juveniles ratio; and on morphology, focusing on the

average weight of individuals. In addition, the microscale factors that most influence the

abundance of the species have been identified. Based on these findings, actions have been

proposed to improve its conservation status. To achieve these objectives, 20 sections of 300

m each were delimited. There we analysed mesoscale variables, which affect the entire

section, and microscale variables, within a radius of 10 m2 of the handles, during the two

visits made between may and june.

The results show that habitat at mesoscale have a greater influence on abundance, sex ratio

and average weight than at microscale; with higher values in areas with low slope and

proximity to the forest. In contrast, the juvenile ratio is primarily and positively influenced by

the presence of aquatic vegetation. Therefore, the main conservation actions proposed are

to maintain or increase areas with gentle to moderate slope, and to maintain aquatic

vegetation coverage above 40% in areas with juveniles

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