Microhabitat use during brumation in the Japanese treefrog, Dryophytes japonicus

Although amphibians undergo drastic changes in physiology and behaviour before hibernation, this phase of their life cycle (i.e., brumation) is the least understood. We investigated the patterns of microhabitat use by Dryophytes japonicus during brumation using a Harmonic Direction Finder to track 27 adults in October 2013. Most frogs used chestnut trees throughout their diel cycle. The species was most active within the "leafy vegetation" microhabitat, moving about 2 m within 72 h on average, and mostly circa 10 AM. Frogs moved less in the four other microhabitats, with individuals moving between 1 m and 50 cm, typically during the early afternoon. Around 3 pm, the microhabitat mostly used was "on bark", with displacements almost totally halted. The use of microhabitats and shelters, as well as movements in relation to time of day, suggests that D. japonicus displays behavioural thermoregulation during brumation. This research is the first providing insights in the brumation ecology of a non-freeze-resistant Palearctic anuran.