Living in discarded containers: spiders explore a new niche created by littering in urban woodlands

Abstract

Increased urbanisation is leading to littering of the environment. However, some animals may adapt to live in such altered habitats. The aim of this study was to assess whether discarded containers can serve as a suitable microhabitat for spiders. The study was conducted in 10 woodland areas in the city of Wrocław, Poland. In September 2018, a total of 939 containers were collected, of which 33.5% contained evidence of spiders having resided therein: webs, dead or living spiders, exuviae or cocoons. A total of 22 species and several other taxa that could not be recognised so accurately were detected. The most common of these belonged to Linyphiidae and Theridiidae. Juveniles (N = 103) dominated over adults (N = 58), and females (N = 34) were more numerous than males (N = 24). In 15 containers, interspecies pairs were found. Among ecological guilds, sheet web spiders dominated (60%) followed by space web spiders (24%), ground hunters (9%), ambush hunters (3%), specialists (3%), and other hunters (2%). Spiders were significantly more often found in colourless (38.3%) and green (35.5%) than in brown bottles (25.2%). They were also more numerous in glass bottles for sweet drinks (50.0%) than in beer bottles (28.0%), and slightly more frequent than in glass vodka bottles (33.3%). Our study showed that discarded containers are fully exploitable microhabitats for spiders and are used by these animals for at least three different purposes: hunting, hiding and breeding, however the effect on their fitness remains unknown.