In recent days, there has been talk of a large species of spider coming back from extinction as its numbers start to increase.

The RSPB has confirmed that there are spiders which can grow up to the size of rats and the population is growing thanks to conservation efforts.

The fen raft spider spent centuries in wetlands in the UK but with the Industrial Revolution resulting in many of the species’ habitats being drained, they almost went extinct in the 20th century, ITV News reports.

Now, the species is said to be “thriving in the UK” after years of conservation work by the charity and Chester Zoo.

Where are rat-sized spiders in the UK?

In 2010, the spider was only known to be found in three areas of the UK but now, 10,000 breeding females are estimated to exist across the UK, reports ITV News.

In Norfolk and Suffolk, the spider is expected to have its best year on record, the RSPB said, as nearly half of the breeding females are thought to be there.

How were the rat-sized spiders brought back from near extinction?

A project which allowed the fen raft spider to breed was formed in 2010 and it meant that the young spiders could be introduced to suitable habitats.

Cantley Marshes, which are RSPB-owned, became the new habitat for the spiders when they were released in 2012. The spiders spread to other surrounding areas nearby.

They managed to make their way to another RSPB-owned site (Strumpshaw Fen) – they were first reported and pictured by a visitor.

Tim Strudwick, reserves manager for the RSPB in the mid-Yare valley in Norfolk, said: "We just don’t know how far they are going to spread and that’s what’s exciting, seeing which bits of habitat they take over next."

He added: "The fen raft spider is one of the UK’s rarest invertebrates and we are proud of the role our reserves and teams have played in its recovery.

“These spiders have an important role in maintaining the rich aquatic diversity found in the grazing ditches on our reserves. The females are impressive in size, but also beautiful – they are truly special to see.”

What is a fen raft spider?

A fen raft spider is brown in colour and can grow to be the size of a rat or a man’s hand.

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They can spin webs that can reach up to 30cm and they are the biggest spider known to exist in the UK – there are 660 species that are known of altogether.

The spider eats a variety of things including dragonflies, small fish and tadpoles and they can run across water.

While they are big and scary to some people, they aren’t venomous and they prefer to live in marshy outdoor habitats rather than indoors.