Field observations on the natural history and breeding behavior of the Atacama Toad Rhinella atacamensis, (Anura: Bufonidae) from Chile

Abstract

Amphibians have diversified predominantly across tropical environments where humidity, temperature and microhabitat availability facilitate demographic stability. However, a number of lineages have colonized extreme deserts, where their diversities are considerably lower. One species in particular, the Atacama toad (Rhinella atacamensis), has adapted to the Atacama Desert, the driest place on Earth. Despite the ecological uniqueness of this species, most aspects of its natural history, reproduction, patterns of activity and behavior remain unknown. Using camera traps and in situ field observations, we report a set of novel natural history findings in a population from the Llanos de Challe National Park. We show that R. atacamensis remains hidden from the sun in small pools under vegetation, where 100% of observed females have a male permanently attached in amplexus at all times. The toads emerge to gather in small ponds after the sunset (~20:00h), where males engage in active contests over females, with up to four males competing for one female. They retreat into the covered pools after ~06:00h. Eggs laid during the night hatch within 24 hours. We discuss these observations in the context of the global diversity of bufonid toads in general, and in relation with the effects that selection emerging from the harsh conditions of Atacama may exert on the expression of these traits.