Why are there 10,000 spiders in the UK?

This week, several newspapers and papers in the United Kingdom reported that 10,000 mammoth spiders, which some say are as big as rats, have been released across the country.

A report in the Daily Mail magazine reads: “Thousands of giant spiders ‘the size of a man’s hand’ have descended on the UK after a zoo decided to release them .”

However, scientists have been making it clear that although thousands of spiders have been deliberately raised and released over the years, they are not “running free” and are not as large as claimed. so.

Here’s what we know about how this story was invented and the real story behind it:

What exactly happened?

In August, the Royal Society for the Protection of Birds (RSPB) and several other conservation organizations announced that giant spiders (also known as fen raft spiders), which are classified as “vulnerable” by the International Union for Conservation of Nature. (IUCN) and as a “Country Rare” in the UK, they were returning to other parts of the country.

Those areas include The Broads, a network of lakes, rivers and Britain’s largest protected wetlands that criss-cross the north-east counties of Norfolk and Suffolk.

The recovery of this spider is the result of many years of intensive conservation by scientists. Before this effort, there was only a “group” of giant raft spiders, UK newspapers say. Chester Zoo estimates that across the UK, there may now be around 10,000 arachnids. According to the RSPB, a recent survey found that the number of female recluse spiders has reached thousands, with an estimated 3,750 in Norfolk alone and its population increasing from three to out of 12.

It’s “a staggering number of species that were previously threatened in 2010 alone,” the RSPB’s August statement said. The species, the organization added, remains vulnerable but is no longer endangered.

The IUCN still lists the spider as vulnerable on its Red List of Threatened Species, a designation given in 1996. Scientists say it is possible that prehistoric spiders were “very abundant”. throughout Europe.

Breeding usually takes place in July and September. RSPB experts have predicted that last year was the “best year on record” for breeding spiders, and it was likely to increase the population.

What kind of spider is it?

Giant raft spiders (Dolomedes plant) is a European species known for its size and white or cream stripes running along the sides of its black or brown body. Spiders, which live for two years, are not dangerous to humans and, because they usually live in humid areas, they are unlikely to be found in residential buildings.

Females are larger than males. In total length, including the length of the spread legs, females can reach 70 millimeters (2.8 inches). If you put one on the palm of an adult, which is on average about 75 millimeters (three inches), the spider would cover the inside.

“This is easily recorded as ‘the size of a human hand’ or perhaps ‘the length of a newborn’… (and by extension) it is extended to ‘the size of rats’,” Dave Clarke, conservationist of animals at the London Zoo, wrote in a blog in September.

However, Chester Zoo, in an X post last week, used the phrase “they grow to the size of your hands”, to describe the spiders.

Ten years ago we helped release HUGE GIANT spiders back into the UK! 🕷️🇬🇧

Fen raft spiders are bred here at the zoo, and we are very happy to report that there are over 10,000 breeding females… 👀… pic.twitter.com/xXvpRe24iU

— Chester Zoo (@chesterzoo) 30 October 2024

Giant raft spiders actively hunt, instead of building webs to catch food. They live in water, and can fly over water surfaces to catch their prey. The tiny hairs on their feet help them sense vibrations in the water. Males also use that hair sensor to communicate with females during courtship, testing their receptivity by scratching the surface of the water. Giant raft spiders eat dragonflies, damselflies, tadpoles and small fish, as well as other spiders.

Females are fiercely protective of their eggs. When breeding, the mother creates an egg sac to carry her hundreds of young – usually for up to three weeks – while she searches for food. Just before the babies are hatched, the spider spins a web of silk the size of a pizza, suspended above the water, to keep the babies safe as well.

In Britain, fen raft spiders live in unpolluted or alkaline canals and fens or sedge meadows with reeds and sedges.

Conservationists say people are unlikely to come across the fen raft spider, as it lives in only a few wetlands in the UK. In some parts of Europe, such as Scandinavia, spiders are found around the edges of natural lakes.

What happened to the spiders?

Giant raft spiders are almost extinct in the UK due to habitat destruction. Scientists have found that in East Anglia, for example, a reduced year-round supply of water to some wetlands – more runoff is being diverted to public water sources – has helped to reduce emissions.

Increasing summer droughts in the UK – due to climate change – have exacerbated the issue, scientists say.

Other parts of continental Europe have also seen a decline in the number of spider rafts. In the Netherlands, evidence suggests that wetlands and wetlands with agricultural runoff or fertilizer have also declined. However, the population is well established in the Baltic States and Scandinavia.

How were they protected?

Between 2011 and 2013, in an effort led by the RSPB, scientists from UK zoos and conservation centers collaborated to breed hundreds of baby spiders in test tubes (so that they would not I eat them).

“Our team hand-feeds tiny flies to each spider using tweezers, day in and day out, for weeks in our bio-secure breeding facility,” the statement said. of Chester Zoo, which was part of. conservation project. “Eventually, the young spiders got strong enough to be returned to their natural habitat, which our partners worked to restore, and we released hundreds of them.”

Clarke of London Zoo, who also participated in the project, wrote in a blog post that the baby spiders were introduced to a “new and suitable environment”, which included protected wetlands. This contradicts the claims of spiders being released across the country.

Clarke wrote that there is no reason to fear the increasing number of spiders as it is unlikely to spread to habitats, saying “This is a huge conservation success, for spiders and the restoration of many areas that have been driving success… Misinformation like this. aggravates arachnophobia [fear of spiders].”