Spatial distribution of male Italian tree frogs (Hyla intermedia) at the breeding site

This paper describes the use of space by male Italian tree frogs (Hyla intermedia) at a small lek. For the entire breeding season 2013, we recorded the positions of lekking males on dedicated data-sheets; then, the collected data were digitized and analyzed. In order to provide insights into the mechanisms responsible for the observed patterns of distribution, we analyzed the data at three levels (population level, single night level and individual level). The analysis at the population level showed a non-homogeneous distribution of males within the breeding site. Consistently, a randomization test showed that, at the single night level, males tended to aggregate in several exhibition centers within the site. Finally, the graphical analysis at the individual level showed 3 different patterns of use of space: site-fidelity (6 males out of 18), random use of space (8 males out of 18) and intermediate behavior between the two (4 males out of 18). These data suggest that the use of space by male tree frogs is not always context-dependent. In particular, we hypothesize that site-faithful males choose their calling location independent of the social context and that they may act as attractors for those ‘site-unfaithful’ males that change their position opportunistically from night to night, in order to place themselves in the areas of highest calling activity.