Burrow decorations as antipredatory devices

Animal decorations are normally interpreted as signals of quality.In spiders, however, decorations may have different functions,including the attraction of prey to the web or making the spidercryptic to predators. To date, there is scant evidence for thelatter hypothesis. Here we use the burrow-decorating wolf spiderLycosa tarantula to test whether turrets around the burrow serveto prevent burrow invasion and predation from the Occitan scorpionButhus occitanus. We located spiders and scorpions in fieldenclosures and manipulated the presence or absence of decorationsor turrets. We found that the presence of the turret decreasesthe rate of burrow invasion and improves spider survival, possiblybecause the turret makes the burrow cryptic to scorpions. Inaddition, a field survey showed that burrows with larger decorationshad a lower chance of being invaded by scorpions. These resultsprovide evidence that the decoration has an antipredatory functionin nature.