One of the UK’s rarest and largest spider species, the fen raft spider, is making a remarkable comeback in nature reserves.

After nearly facing extinction over the past century, the population of fen raft spiders has been steadily increasing, reaching a record high this year, according to the conservation charity RSPB.

Fen raft spiders, known for their impressive size with a leg span of up to 7 cm, also create remarkable nursery webs that can reach up to 25 cm in diametre.

The resurgence of these giant spiders is credited to dedicated conservation efforts aimed at reintroducing them to restored habitats.

This conservation project is a collaborative effort involving Suffolk and Sussex Wildlife Trusts, Natural England, the Broads Authority, the RSPB, and the British Arachnological Society.

The species’ rarity is primarily due to “large-scale degradation and destruction of the lowland wetland habitats” on which it depends. However, by reintroducing spiders to suitable sites in the Norfolk and Suffolk Broads, conservationists have successfully established sustainable populations.

A recent survey estimates the total number of female fen raft spiders to be 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 ideal environment, rich in prey and with the right mix of vegetation.

In addition to their size, fen raft spiders are easily identified by a white or cream-coloured band along their dorsal surface. These semi-aquatic ambush predators use tiny hairs on their legs to detect faint vibrations on the water’s surface, allowing them to hunt insects, dragonfly larvae, other spiders, tadpoles, and even small fish.

Despite their size, fen raft spiders are harmless to humans. The success of this project underscores the importance of conservation efforts in restoring endangered species.

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.”

 

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