Giant spiders crossing the UK? This was announced yesterday by Chester Zoo, 10 years after their release. Don't panic, they're not as big as Aragog in Harry Potter or Shelob in the Lord of the Rings. These are the size of a hand, and are harmless. While this represents a nightmare for arachnophobes, it's actually good news when it comes to wildlife rehabilitation.
Rescued by Chester Zoo
About ten years ago, Chester Zoo released thousands of raft spiders (Dolomedes plantarius) in the wild, after having raised them, to try to prevent the disappearance of the species. Today, the initiative has borne fruit: “ there are now over 10,000 breeding females and they have just experienced the largest breeding season on record!”, welcomes the zoo.
The species has benefited from a conservation program, born from a collaboration with the Royal Society for the Protection of Birds (RSPB). A partnership celebrated by the zoo onWe are very proud to be part of this conservation breeding rescue programme, working alongside our friends at the RSPB to prevent the raft spider from becoming extinct”.
Meticulous work, the goal being that they do not eat each other. It was therefore necessary to raise the spiders individually: “Our team delicately hand-fed each of the hundreds of baby spiders with tiny flies using forceps, day after day, for weeks in our bio-secure breeding facility,” says Chester Zoo.
Spiders saved from extinction
Fifteen years earlier, the raft spider was close to extinction. Once widespread in Western Europe, its population has declined significantly in recent decades. It is also the only spider from this region of the world to be included on the red list of threatened species of the International Union for Conservation of Nature (IUCN).
Its rarity is explained in particular by the fact that it is a species that developed during interglacial periods. The melting of the glaciers created immense wetlands, favorable to their prosperity. These spaces are now under attack, specifically for environmental reasons.
Since 1960, the extent of these zones has declined. Global warming has disrupted the balance of these spiders, forcing them to adapt to new conditions, or to migrate to new regions. Here too the problem arises, because they are dependent on their contact with water. In other words, migration by land is not possible, which prevents them from settling elsewhere.
The essential role of the raft spider
According to Tim Strudwick, site manager at RSPB Mid Yare Nature Reserve in Norfolk, this arachnid species is particularly useful: “These spiders play an important role in maintaining the rich aquatic diversity found in the grazing ditches of our reserves.”
The raft spider is a semi-aquatic hunter. Its way of life contributes to maintaining the balance of its ecosystem in a marshy environment. It thus regulates the populations of the insects it prefers, including flies, tadpoles and dragonfly larvae. The arachnid even eats some small fish.
As its name suggests, its playing field is on the surface. She does not weave webs but hides before attacking. Equipped with hairs on its legs, called trichobothria, it senses the vibrations in the water created by its prey, which allows it to anticipate its movements and reach its target.
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