Weather patterns and daily torpor in free-ranging animals

Torpor was investigated in free-ranging tawny frogmouths (Podargus strigoides: Caprimulgiformes) and sugar gliders (Petaurus breviceps: Marsupialia) near Armidale, NSW, Australia. Both nocturnal species entered torpor regularly. Torpor was most frequent in June/July/August (frogmouth: 50.4%; sugar,glider: 22.3%), the three coldest months of the year. Both species entered torpor preferably during their normal activity phase. While sugar gliders extended torpor into the rest phase, frogmouths always aroused before sunrise, but often commenced a secund torpor bout around dawn. Low T-a, was the main stimulus for the expression of torpor, but for sugar gliders rainfall was also important. It appears that inclement weather conditions not only increase thermoregulatory costs, but more importantly, prevent successful foraging in both species. Therefore, torpor cannot balance the daily energy budget, but is nevertheless important to stretch body energy reserves, which can be replenished only irregularly.