Behaviour 2019
The quiet before the storm: Red howler monkey calls do not predict rain in Ecuador
Anna M Kurtin1, Anthony Di Fiore1, Luciana Oklander1,2, Silvy Van Kuijk1. 1The University of Texas at Austin, Austin, Texas, United States; 2Grupo de Investigación en Genética Aplicada, Universidad Nacional de Misiones y Consejo Nacional de Investigaciones Científicas y Técnicas, Posadas, Misiones, Argentina

This study tests a widely-held folk belief in Central and South America: howler monkey long-range calls are associated with the onset of rainfall. We hypothesized that howler monkeys respond vocally to changes in ambient conditions or acoustic signals of incoming weather and that these vocalizations can be used to roughly predict incoming rain. To address this question, we analyzed 50 days of passive acoustic recordings collected at the Tiputini Biodiversity Station in the Ecuadorian Amazon. We used the software Audacity to listen to and create spectrograms of recordings, from which we extracted the start times of howler monkey (Alouatta seniculus) long-range calls and bouts of rain. Using a permutation test, we investigated the temporal relationship between the onset of rain and howling within each day to analyze whether rainfall events are preceded by howling within one hour more often than would be expected by chance, and, conversely, whether howling events are followed by rainfall within one hour more often than expected by chance. Our prediction of an association between howling and rain was not supported, and we propose three explanations as to why this folk belief persists.