Dragonflies and the thermal landscape: implications for their conservation (Anisoptera)

The National Botanic Gardens, Pietermaritzburg, South Africa are being partially ecologically landscaped. Odon. are one of the subject groups for conservation. Their behaviour relative to the topography and thermal patterns of the landscape were studied. Several spp. of Anisoptera used the vegetation, rocks, gravel and sand substrates for perching. There were distinct species- and sex-specific behavioural responses to the shape and features of the landscape. By selecting certain microhabitats. and substrates, the dragonflies gained extra warmth late in the afternoon, particularly late in the season. Rock-basking was particularly prominent, as was aggregating in a sheltered hollow. These behavioural patterns apparently allowed longer periods of activity, especially for hunting crepuscular prey and searching for suitable roosting sites. Rocks and the hollow were not used at night when cold-air drainage made the habitat too cold. These behaviours are important in the lives of the dragonflies, to the extent that local topography and landscape features should be considered when managing areas for dragonfly conservation.