Climatic disturbances like droughts and hurricanes are major forces regulating the population dynamics of terrestrial fauna elsewhere. In Puerto Rico (PR), a severe drought occurred between 2015 and 2016, and herein we document the population dynamics of the Yellow-chinned Anole, Anolis gundlachi. This is a thermoconformer lizard, vulnerable to dehydration and inhabits closed-canopy forests. We monitored its abundance monthly using nocturnal visual surveys in four 4x30m transects (480m2) for a 4-year period (2014 to present) in a tropical montane forest in the Sierra de Cayey, PR. The main objective of this study is to examine the influence of this drought on the population dynamics of Anolis gundlachi. 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 lizard. We collected data on rainfall from our study site from June 2014 to present 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 (>40mm SVL), large juveniles (~20-40mm SVL) and recently hatched juveniles (<20mm SVL, a proxy for recent reproduction) of A. gundlachi to address our objective.
Results/Conclusions
The abundance of all lizards 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. Between 2014-2015 (425 days of drought), 91.5% of the time consisted of days with rainfall below the threshold to avoid hydric stress. Small juveniles showed a 9-month lag-time response to the drought and their abundance decreased with increases in rainfall deficit (r=-0.3520, p<0.0482, n=32), but did not change once the drought dissipated. Large juveniles did not show an obvious pattern attributed to the drought. Adults showed a lag-time response to the drought, but from a 9-month to a 12-month delay-period, and their abundance decreased significantly with the increased rainfall deficit. However, their abundance increased steadily once the influence of the drought dissipated (r=0.4469, p<0.0024, n=44), but the reasons for this increase are not clear. Unfortunately, Hurricane María stroke PR in September 2017, devastated our study-site and generated microclimate conditions presumably detrimental to this lizard, which requires the continued monitoring of this population to examine its long-term response to sequential climatic-disturbances at this mountain site.