Why are there so many spiders on the Kings Ave and Commonwealth Ave bridges in Canberra?

Over summer, Madeline Cooper noticed a huge build up on spiders on the two bridges that cross Lake Burley Griffin. It prompted her to ask: Is there something about the bridges that make them good spider homes? Tom Storey, an intern from the University of Canberra, accepted the challenge and met Madeline on the Commonwealth Avenue bridge with terrestrial invertebrate expert Dave Rowell. Photo: Mike Leonard on Flickr