TERRESTRIAL AMPHIBIANS INHABITING AN URBAN XERIC ECOSYSTEM: AN ASSESSMENT OF FROGS AND SALAMANDERS IN PROTECTED AREAS FROM MEXICO CITY

Abstract

Amphibians are particularly sensitive to disturbances caused by urbanization. Urban disturbances impact amphibians at different ecological scales that include a decrease in biodiversity, increment of stress, and changes in vocal behavior. However, little is known about urban effects on terrestrial amphibians. In this study, we quantified abundance (by encounter rates) and species richness of amphibians, and the characteristics of their habitats in Pedregal del Xitle, a xerophytic ecosystem in Mexico City. In addition, we evaluated the vocal activity of Pedregal frogs under different noise exposures within the three protected areas. During 2015 and 2016 with the support of volunteers, several stratified direct night searches were conducted in three urban protected areas. Additionally, using a non-supervised classification of satellite images, we analyzed the coverage of the different vegetation types, and calculated the evenness of amphibians. With an effort of 238 person-hours, we located 73 individuals of amphibians, including three plethodontid salamanders (Aquiloeurycea cephalica, Chiropterotriton orculus and Pseudoeurycea leprosa), and the Pedregal frog, Eleutherodactylus grandis. Altogether, the captures of C. orculus and E. grandis represented 90% of the amphibians found. We found that 75% of the amphibians occupied the rocky ground microhabitat. The call rate of E. grandis was consistently lower at sites with the highest noise exposure. Among the three urban protected areas, Ecoguardas stands out as the one with the greatest abundance and diversity of amphibians and the largest proportion of forested area. Our study revealed the ecological value of the Pedregal ecosystem for terrestrial amphibians, since the most threatened species (the frog E. grandis and the salamander C. orculus) are those with the greatest presence in the urban protected areas studied.