Unexpected high overwintering survival rate of the cavity-dwelling ant Temnothorax crassispinus (Hymenoptera: Formicidae)

Abstract

The mortality rate of many invertebrates is high during winter. The survival rate of the ant Temnothorax crassispinus, which overwinters aboveground, was investigated. Unlike previous studies, this one showed a high survival rate during winter. In the field experiment, the number of workers at the end of the experiment amounted to 86-120% of the initial numbers, and 73 out of 74 queens survived. The high survival rate was most likely a result of the favourable weather conditions. In the laboratory experiment, none of the workers exposed to -24°C survived, while the survival rate of workers kept in 5°C was higher (73.2% on average) than those in 0°C (53.2%). The expected rise in temperatures as a consequence of climate change may result in a higher survival rate in the winter season, but also in the reduction of snow cover, which may exert the opposite effect.