We used miniature tags and extensive behaviour observations under natural conditions to describe the movement patterns of over three hundred poison frogs belonging to three different species, which differ in their behaviour and male-female roles in parental care. Poison frog parental care primarily consists of parents transporting their tadpoles from land to small water accumulations where tadpoles can develop. In some species, females revisit the tadpoles and feed them by laying unfertilized eggs. We could show that the movement patterns and sex differences in movement scale are primarily shaped by poison frog parental behaviour. In species where males perform the parental duties, males move more because they transport and disperse tadpoles. In species where females take care of the tadpoles, females have larger home ranges and more complex movements than males.
We then compared the navigational abilities of males and females by translocating frogs away from their home territories and tracking their movements as they tried to navigate back home. Contrary to the widely accepted hypothesis that sex differences in reproductive strategies predict sex differences in spatial abilities, we found that poison frog parental roles did not predict sex differences in navigation skills. Males were better at navigating only in one out of two species with male parental care, and we found no sex differences in the species with female parental care. In addition, males were more explorative in all three species regardless of differences in reproductive strategies and parental roles. We could then show that poison frog males have higher testosterone, just like mammals, and we found that higher testosterone levels were associated with more exploration and higher navigational accuracy. Overall, our results do not support the widely accepted paradigm that sex differences in navigational abilities are adaptations to sex differences in movement range and reproductive strategies. Furthermore, our findings suggest that, like in mammals, sex hormones influence amphibian spatial behaviour.
We also studied the neural mechanisms of amphibian spatial behaviour. We found that medial pallium, the brain area responsible for spatial cognition in mammals, was also activated in poison frogs while exploring a novel environment in the lab. However, different forebrain regions were activated when navigating home under natural conditions. These first findings indicate that despite being very distantly related to mammals, frogs share some neural machinery supporting spatial behaviour. But the mechanisms allowing complex navigation over long distances in the wild might be amphibian-specific and have evolved independently. Finally, we also performed experimental and analytical work revealing that, just like mammals, poison frogs rely on flexible spatial memory for navigation. Such cognitive abilities have been previously considered unique to mammals and birds, a view which our findings challenge.
The outcomes of our research have been presented at four international scientific conferences and communicated to broader audiences in public lectures, webinars, and educational videos. In addition, all data and results are being published in peer-reviewed scientific journals and made freely available according to Open Science standards.
