Increasing hurricane frequency and intensity have become one of the most significant threats to the viability of animal populations inhabiting tropical and subtropical regions. Yet, we lack studies that have examined the effects of extreme conditions such as hurricanes on individual life histories. This is significant because testing predictions regarding ecological and evolutionary population dynamics requires an understanding of the diversity of life histories among individuals, since life histories shape demography, which in turn drives evolution. In this study, we aim to investigate the consequences of a major hurricane on individual-level heterogeneity in life histories. We use long-term demographic data on the Cayo Santiago rhesus macaques before and after Hurricane Maria, a category 4 hurricane in 2017 entering the archipelago of Puerto Rico through Cayo Santiago. Following a year from the onset of the 2017 birth season, we quantify variability in the reproductive stages during an individual’s lifetime in a stage-structured population model and measure population entropy of the Markov chain, which computes the rate of diversification of individual life histories.
Results/Conclusions
Pre-hurricane data based on 3,909 individuals show that the population of Cayo Santiago rhesus macaques has a relative high rate of diversification of individual life histories with annual population entropy ranging from 0.54 to 0.80 over 40 years. The mean stable stage distribution during pre-hurricane years resulted biased toward nonbreeders with 23.2% infants, 51.0% nonbreeders, 3.18% failed breeders, and 22.7% breeders. Given that the hurricane occurred during birth season, we expect an increase in the proportion of failed breeders (females giving birth to a non viably offspring) following the event. We also predict that the hurricane serves as a major driver of individual life histories, leading to a single more optimal life history and thereby reducing entropy. This is important as a reduction in entropy translates into a reduction in the variability that natural selection can act upon. In this way, our study gives us new insights about the underlying drivers of individual heterogeneity within populations and potential evolutionary mechanisms following extreme events.