We examined the ecophysiology of hibernation in boreal Leptotharax (sensu stricto), the ant genus which ranges farthest north in Eurasia and North America. In laboratory experiments, overwintering workers and queens of L cf. canadensis from Québec and New England survived -15°C without increased mortality, and one fifth of all individuals were alive even after 48 hours at -25°C. Mortality rates were significantly higher in solitarily overwintering ants than in ants hibernating in the winter clusters of their colonies. This is probably due to an increased starvation risk in isolation. Dissections showed that the crop was empty in all workers surviving solitary hibernation for 110 days, but only in approximately 2/3 of the workers hibernating in groups. Food exchange by trophallaxis was observed in overwintering groups. Though ants are generally considered to be inactive in winter, workers and queens of L cf. canadensis exhibited basically the same behavioral repertoire as in other seasons, with the exception of foraging and egg laying. Especially later in winter, the percentage of individuals immobile in the hibernation cluster increased. The results of our study are discussed in respect to the life history strategies of Leptothorax (sensu stricto) and the frequent occurrence of multiply-queened societies in subarctic and boreal habitats.
- Cold resistance
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics