Overwintering dragonflies in an African savanna (Anisoptera: Gomphidae, Libellulidae)

To better understand overwintering capability of dragonflies in the African savanna, observed individuals were placed into predetermined age categories at sites along the Mogalakwena river, Limpopo province, South Africa, during mid-winter. Age categories were determined by degree of wing wear each individual had sustained. The Dragonfly Biotic Index (DBI) was used to categorize spp. into rare, widespread generalists versus rare, narrow-range specialists. All the recorded spp. were common, widespread generalists, occupying microhabitats created by the winter dry season decrease in water level and flow rate, and able to survive seasonal habitat changes. Seven of the 8 spp. were libellulids, and 1 gomphid. Their ability to thermoregulate by selecting appropriate perch sites, in addition to their high habitat tolerance, plays an important role allowing them to survive as adults throughout winter. It is confirmed that the libellulids observed here were highly habitat tolerant, common and widespread spp. whose success comes about at least partly from their ability to overwinter and be ready to take advantage of the first rains.