Movement ecology of tropical amphibians: automated tracking

Understanding animal movement is critical for developing deeper insights into natural history of species, the functioning of ecosystems, and the global patterns of organism distribution. However, tracking small animals in complex habitats, such as amphibians in the tropical rain forest, remains a major challenge. Tropical amphibians are facing a dramatic decline while even basic movement patterns of most species remain unknown. Automatization of radio tracking techniques is essential for collecting data on local movements from a large number of individuals from a variety of species in diverse environments. In this project, we will field test a novel automated radio-tracking system and use it to study movement ecology of two emblematic amphibian species from South and Central America: the dyeing poison frog (Dendrobates tinctorius) and the tngara frog (Engystomops pustulosus). Until now, tracking studies of amphibians have focused almost exclusively on temperate regions. Meanwhile, tropical amphibians display a variety of complex social behaviors such as aggressive territorial defense and parental care but the associated movement patterns remain largely unknown. The dyeing poison frog is a colorful, toxic, day- active, voiceless frog known to shuttle its tadpoles on its back to water-filled tree holes. The tngara frog is a cryptic, night-active frog known for its distinct mating calls and building of foam-nest in small forest ponds. Both species depend on unpredictable and temporary forest pools for reproduction. We will investigate how the combination of these environmental factors, reproductive behaviors, and spatial orientation abilities result in similarities and differences of movement patterns between the two species. Going beyond descriptive science, we will link individual movements to factors, such as the cognitive abilities of the animals and the patterns of population genetics. This knowledge is essential for understanding evolutionary processes that shape individual behavior and structure populations, as well as for applications in conservation science.

Studying animal movement is critical for understanding species natural history, animal sensory and cognitive abilities, and the functioning of ecosystems. However, tracking small animals in complex habitats, such as amphibians in the tropical rainforest, remains a significant challenge. The goal of this project was to advance our understanding of movement ecology of tropical frogs. Specifically, we investigated how the differences in environmental factors (e.g., weather and water availability), reproductive behaviors (e.g., territoriality and parental care), and navigational abilities (e.g., spatial memory flexibility) shape the movement patterns of rainforest frogs. Working together with a team of national and international collaborators, I used tracking techniques to quantify the space use of three day-active poison frog species and one small night-active rainforest frog that lives in a similar habitat. Overall, the frog space use was characterized by site fidelity and sedentary habits with intermittent long-distance movements, mostly related to their reproductive resource exploitation. In other words, frogs could spend days and weeks without leaving a small area of a few meters and then move tens to hundreds of meters over a short time to visit a distant pool. In contrast to temperate region amphibians, these movements are not seasonal coordinated migrations. While frogs tended to move more with higher rainfall and lower temperature, each frog showed distinctive individual patterns of movement mostly dependent on their reproductive state. Species and sexes also showed consistent differences in their space use shaped by their life history and resource distribution. For example, poison frogs lay their eggs on land, but their tadpoles are aquatic, and for the tadpoles to survive after hatching, parents must shuttle their tadpoles from land to water pools. Depending on the species, either males or females typically transported the tadpoles, had a more extensive space use, and moved more frequently. Species that used more abundant and more stable pools, such as plants filled with water had an overall smaller space use than species that used more dispersed and less stable pools, such as small ephemeral rain-flooded areas. The movement patterns of all species indicated accurate spatial memory for essential resources. We also experimentally tested the navigational abilities and spatial memory in poison frogs. We found strong evidence that these small frogs form and use a cognitive map of their surrounding area for navigation. Spatial memory is fundamental to the survival and reproduction of these frogs. These findings question the traditional view of vertebrate cognition, which often portraits amphibians as lacking advanced learning abilities and behavioral flexibility. Our findings have fundamental implication for our understanding of amphibian behavior and potential applications in conservation. Tropical amphibians are facing a dramatic decline while even basic movement patterns of most species remain unknown. The movement and natural history data obtained during this project can be integrated into conservation management decisions and ecological modeling that informs conservation policies. The data collected and the fundamental questions raised about the factors shaping the frog spatial behavior will provide the basis for formulating and testing new hypotheses in movement ecology, animal cognition, and neurobiology.