Climatic disturbances are major forces regulating the population dynamics of terrestrial fauna, particularly amphibians. In Puerto Rico (PR), a severe drought occurred between 2015 and 2016, which would have profound consequences for our amphibians. The Puerto Rican Mountain Coquí, Eleutherodactylus portoricensis (28-37mm SVL), is an anuran classified Endangered by the IUCN. It is adapted to conditions of low variability in low temperature and high humidity, conditions typical of tropical mountain-forests. We monitored the abundance of this species monthly using visual and acoustic surveys in four 4x30m transects (480m2) for a 4-year period (2014 to present) in the Sierra de Cayey, PR. The main objective of this study is to examine the influence of this drought on the species’ population dynamics. We conducted a literature review and contrasted the number of days with less than the minimum rainfall required to avoid hydric stress for this species of frog. We collected data on rainfall from our study site from June 2014 to present, which covered the period of this drought, and contrasted the deficit in rainfall compared to the historic deficit in rainfall (50-years of data for the region). We used the mean abundance of adults and recently-hatched/small-sized juveniles (<10mm SVL) to examine their relationship with rainfall at our study site. Under laboratory conditions, hatchlings reach adulthood in 22 months, and we use this estimate to examine the influence of this drought on recruitment.
Results/Conclusions
Similar to other Eleutherodactylus, the abundance of adults and juveniles increases during months with more rainfall and higher temperature, and decreases during months with lower temperature and less rainfall. Compared to historic deficits, 13 months exceeded the total number of days resulting in hydric stress at our study site. Specifically, between 2014-2015 (425 days of drought), 91.5% of the time consisted of days with rainfall below the threshold to avoid hydric stress in this species. The abundance of juveniles decreased with increases in rainfall deficit (r=-0.5527, p<0.0004, n=37), and correlated with a decrease in the abundance of adults (r=0.5555, p<0.0073, n=22). Currently, the population fluctuation remains within after-drought values, which suggest that decreases in the abundance of this species have been halted, presumably indicative of short-term resilience. Unfortunately, Hurricane María stroke PR in September 2017, devastated our study-site, and generated microclimate conditions typical of lowland areas. We continue the monitoring of this population to find the consequences of these sequential climatic-disturbances on the persistence of this species.