Ecological preferences of Hyla molleri in the colonisation of arboreal refuges in a human-shaped wetland

Abstract

Hyla molleri is well adapted to arboreal microhabitats, which are used among breeding seasons. This species is common in wetlands across the Iberian Peninsula and is therefore vulnerable to the loss and degradation of these ecosystems. Due to its secretive habits, the knowledge about the ecology of H. molleri, outside the breeding season, is still scarce. Using artificial refuges as a proxy to natural refuges, we studied how H. molleri uses arboreal microhabitats near reproductive areas and which environmental drivers influence refuge colonisation. We installed 70 PVC pipe refuges in isolated trees and tree patches. Pairs of pipes were installed at two different heights and monitored fortnightly, for four consecutive days, for one year. Each sampling day, we registered the values of variables related with seasonality, microhabitat, dominant plant species, weather and site fidelity. We recorded 2234 individual colonization events by H. molleri, including 516 multiple colonization events, with a maximum of nine individuals in a single refuge. Refuges that were colonized before were more likely to be colonized again. Additionally, colonization was lower in spring and summer and higher in tree clusters than in isolated trees. We found no significant differences on the height or temperature of colonized versus non-colonized refuges. Our results highlight the importance of adequate arboreal microhabitats and the need for the conservation of terrestrial habitats around breeding areas. We also show that artificial refuges can be useful for H. molleri and similar species, namely for habitat improvement or the implementation of citizen-science and monitoring programs.