Daily torpor in relation to photoperiod in a subtropical blossom-bat, 'Syconycteris australis' (Megachiroptera)

Daily torpor in many temperate-zone mammals is affected by photoperiod. As little is known about the effects of photoperiod on torpor in subtropical species, we investigated whether, and if so how, torpor use, duration, and depth are affected by acclimation to three photoperiods (short, intermediate, long) in the blossom-bat 'Syconycteris australis'. In contrast to many other studies, torpor occurrence, duration, and depth did not significantly respond to photoperiod acclimation in 'S. australis'. Interestingly, the trend of a decline in torpor use under long photoperiod was the opposite of that observed previously in 'S. australis', which had been captured from the wild in summer and winter. Our study suggests that some species living in low latitude areas with unpredictable weather like 'S. australis' may not use photoperiod for seasonal adjustments in physiology because it is not a reliable cue for food availability.