In our Division we study a broad range of questions in Neotropical poison frogs – spanning from reproductive ecology and cognition, to population dynamics.
Poison frogs (Dendrobatidae) belong to a neotropical frog family of some 300 different species that differ vastly from the stereotypical frog. They are active throughout the day, exhibit strong territoriality, and lay their clutches on land. Many of them are brightly coloured, which indicates high levels of toxicity to potential predators. The dilemma of terrestrial clutches that will develop into aquatic tadpoles – able to breath in water only through gills – has been “solved” in these frogs via parental behaviours: Adult frogs take their hatched tadpoles piggy-back across the rainforest to water bodies, and sometimes they have to cross quite large distances to accomplish this duty.
One of our main study organisms is the Brilliant-thighed poison frog Allobates femoralis, which is non-toxic and shows a rather cryptic coloration, but has proven to be an optimal model for studying mating and parental behaviour.
This species is widely distributed across Amazonia and the Guiyana shield. During the breeding season, males are highly territorial and broadcast territory occupancy with a prominent advertisement call that is aimed at both attracting nearby females and also warning male competitors not to come closer.
Females decide when and with whom they want to mate. They approach calling males and thereby initiate a very extended and complex courtship behaviour. During courtship, the male guides the female across his territory and presents her with various possible egg deposition spots in the leaf litter – a process that can take many hours! After a clutch has been deposited, the female leaves the male’s territory and goes back to her resting site outside the male’s territory.
The male remains in his territory and will transport the clutch to widely distributed water bodies as soon as tadpoles hatch about three weeks later. Tadpoles are deposited in a variety of medium-sized terrestrial water bodies, such as floodplains, water-filled depressions, palm fronds and holes in fallen trees, which are located up to 200 m from the males’ territories.
Studies in the field
We study A. femoralis in their natural habitat, close to the CNRS research station ‘Saut Pararé’ (4°02´ N, 52°41´W; WGS84; www.nouragues.cnrs.fr) in the nature reserve ‘Les Nouragues’ in French Guiana, where we have been conducting research on the species since 2008. Beside our studies in a natural A. femoralis population, we monitor an experimental population on a river island of ~5 ha in size, that was installed in 2012 by introducing 1800 tadpoles from the nearby mainland population onto the island.
The laboratory population is located at the Ethological Research Station Hasli from the University of Bern. All frogs are housed in glass terraria of equal size (60x40x40 cm) with identical equipment and furnishing. An automatic raining, heating and lighting system ensures standardized climatic conditions with parameters similar to the natural conditions in French Guiana in all terraria. Frogs breed regularly and show relevant behaviours (e.g. advertisement calling, tadpole transport, courtship, cannibalism, …) comparable to natural conditions.