Female oviposition site selection influences hatching success and embryonic development in a Neotropical glass frog

For oviparous animals, the decision of where to lay eggs is critical, as offspring remain sessile from oviposition through hatching and are thus unable to escape unfavorable conditions. Consequently, females are expected to select oviposition sites that benefit embryo development and survival. This may be particularly relevant for arboreal frogs, which typically lay eggs on leaves overhanging water, where embryos are exposed to predation, desiccation, and other risks until hatching. Yet studies directly linking maternal substrate choice to embryo survival remain scarce. Here, we examine how oviposition substrate influences embryo survival in the Emerald glass frog (Espadarana prosoblepon), a species in which females deposit eggs on multiple substrates, providing a rare opportunity to test how oviposition decisions affect reproductive success. Monitoring clutches in situ, we compared microclimatic conditions, hatching success, and sources of embryo mortality between the most used substrates: the spike moss Selaginella diffusa and leaves. Additionally, we conducted a two-choice experiment in semi-captivity to test whether females preferentially select one substrate over the other. Although microclimatic conditions did not differ between substrates, hatching success was significantly higher on S. diffusa, which also experienced less predation. In the two-choice experiment, all females laid their eggs on S. diffusa, and those clutches had higher hatching success and faster embryonic development rates than those on leaves. Together, these results support the hypothesis that non-random oviposition site selection in E. prosoblepon is driven by the maximization of embryo survival, demonstrating that substrate choice has measurable fitness consequences for the offspring.