In a hole in the ground there lived a spider: Microhabitat preference and burrow architecture in natural populations of Sydney funnel-web spiders (Atrax robustus)

Abstract: The microhabitat an animal occupies is expected to be selected for and optimal for that animal. However, little is known about the microhabitat features selected by small sedentary animals such as ground dwelling spiders. In this study we investigate the microhabitat preferences of the Sydney funnel web spider, Atrax robustus, in the wild. We show that the spiders select microhabitats characterised by certain substrates and structural features for their burrows. In particular, A. robustus individuals strongly prefer to burrow against solid structures such as rocks or trees. Above ground, all burrows had silk triplines radiating from the burrow entrance with variable amounts of silk ‘funnelling’ present, ranging from triplines alone to extensive silk tubing (funnel). Below ground, the burrows were always associated with a tree root or a rock and typically had a single tunnel ending in a widened chamber. However, burrows varied considerably in size, direction and shape, usually twisting to follow the contour of the root or rock underground. The insights gained from this study can inform future conservation efforts of small, sedentary terrestrial animals, as well as increasing our understanding of Sydney funnel-web spider ecology.