More than 150 spiders fostered by Bristol Zoo Gardens released into the wild

After ten weeks of careful husbandry at Bristol Zoo, 172 tiny fen raft spiderlings are set to be released into the wild.

The young spiders have been raised by keepers at Bristol Zoo as part of a conservation rearing project to help save this native species, which is one of Europe's largest but least common spiders.

The spiders are so rare that they are protected by law in the UK and have been classified as 'Vulnerable' on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. They are only found in three sites in Britain – Norfolk, East Sussexand South Wales.

The 12 week old spiderlings, which were just two millimetres in size when they arrived, received intensive care by experts in Bristol Zoo's Bug World - a process that took several hours every day and included being hand-fed flies.

Carmen Solan, invertebrate keeper at Bristol Zoo said: "They have grown from tiny dots to 4-5mm long. It's been an amazing project to have been involved in, we're rather sad to see them go! "

Mark Bushell, Assistant Curator of Invertebrates at the Zoo, added: "The aim was to give these little spiders the best possible start in life, which is something we're very proud to have achieved. The spiders leaving us are healthy and strong, well equipped for a life in the wild."

The young spiders will be released into wild fenland habitats in Norfolk to begin their adult lives. These semi-aquatic spiders can grow to approximately 7cm in leg span and live for around three years.