One of UK’s largest and rarest spider species making a comeback, says RSPB | Spiders

One of the rarest and largest species of spider in the UK is said to be making a comeback on nature reserves.

After facing near extinction over the last century, the UK’s population of fen raft spiders is steadily increasing, and numbers are at a record high this year, according to the conservation charity RSPB.

Fen raft spiders can have a leg span of up to 7cm and are known for their incredible nursery webs that can measure up to 25cm.

The RSPB said the resurgence of these giant spiders is the result of conservationist work undertaken to reintroduce them to suitable areas of restored habitat.

The project was a collaboration between Suffolk and Sussex Wildlife Trusts, Natural England, the Broads Authority, the RSPB and the British Arachnological Society.

Conservationists said the rarity of the species was mainly down to the “large-scale degradation and destruction of the lowland wetland habitats” on which it depends. However, introducing spiders to sites on the Norfolk and Suffolk Broads has increased the number of sustainable populations needed for the species to thrive. A recent survey estimated that the total number of female fen raft spiders is now just under 4,000.

The RSPB described a “sensitive restoration of grazing marshes by reserve teams across the RSPB Mid-Yare reserves, which includes Strumpshaw Fen, Buckenham Marshes and Cantley Marshes”. These efforts have provided the spiders with an environment with plenty of prey and the ideal mix of vegetation.

As well as its distinctive size, the spider can be recognised by a white or cream coloured band along its dorsal surface. The spider, a semi-aquatic ambush predator, has tiny hairs on its legs that detect even the faintest vibrations on the water’s surface, allowing them to effectively hunt. Their diet consists of insects, including dragonfly larvae, other spiders, tadpoles and fish.

Many will be pleased to know that the giant spider is harmless, and poses no threat to humans.

Experts said that the success of this project has demonstrated the importance of conservation efforts for species restoration. Jane Sears, an RSPB ecologist, said: “The RSPB has played an important role in the reintroduction of these spiders and means we must continue to restore, manage and protect the wetland habitats where the fen raft spider thrives to ensure the future of not just this species, but many others too”.