One of the rarest spiders on earth has bred at Bristol Zoo Gardens in a world first.

Over 1,000 tiny Desertas Wolf Spiderlings have hatched in the Zoo’s Bug World. So valuable are the babies, some have even been hand-reared by dedicated keepers from tiny eggs.

The hatchings are a huge boost for the species, which is only found in one valley on one of the Desertas Islands, near Madeira, Portugal. There is thought to be a single population of just 4,000 adult spiders left in the wild – an alarmingly small number for an entire invertebrate species.

It is hoped that some of the spiderlings can be returned to their native island in the future to boost dwindling numbers in the wild.

Photo Credits: Bristol Zoo Gardens

Desertas Wolf Spiders (Hogna ingens) are classified as “Critically Endangered” on the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species but are not protected by any specific legislation.

The baby spiders are just 4mm in diameter but grow to be huge, impressive-looking black and white adults up to 12cm in size with a body size of 4cm. They are under threat from habitat loss, due to invasive grass binding the soil where they burrow and blocking their natural shelters.

Bristol Zoo has joined forces with Instituto das Florestas e Conservação de Natureza (IFCN) and the IUCN to develop a conservation strategy to protect the species in an effort to prevent it becoming extinct.

As part of the vital conservation effort, Bristol Zoo’s Curator of Invertebrates, Mark Bushell, travelled to Desertas Grande last year with Zoo vet Richard Saunders and collected 25 Desertas Wolf Spiders to be brought back to the Zoo to breed as a ‘safety net’ population.

The effort has been a great success, as Mark explains: “Because this was the first time this species had ever been taken into captivity to breed, it was a steep learning curve. After some of the female spiders were mated, it was an anxious wait to see if they would produce egg sacs. We were thrilled when they did, and to see the tiny spiderlings emerge was fantastic – a real career highlight.”

Such was the keepers’ dedication, that when one of the female’s egg sac broke, eggs were carefully transferred into a miniature incubator for rearing. Once the eggs hatched, they were put into separate containers with sterilized soil, kept in quarantine and individually fed with fruit flies.

Bristol Zoo now plans to send hundreds of the tiny spiderlings to other Zoos in the UK and Europe to set up further breeding groups as part of a collaborative conservation programme for the species.

Mark added: “Establishing the world’s first captive breeding programme for this species is a fantastic step towards protecting it for the future. It is a beautiful and impressive creature, but its natural habitat is being altered by invasive plants. There are simply not enough rocky and sandy areas of habitat left for the spiders to burrow and hide in. The result is a deadly game of musical chairs, whereby the spiders are competing for fewer and fewer burrows.”

Mark added: “In addition to the loss of habitat, one single catastrophic event could wipe out the species entirely. Now we have successfully created a ‘safety net’ population here at Bristol Zoo to help safeguard this impressive creature for the future.”

In future it is also hoped that Bristol Zoo’s team of horticulture experts can visit Desertas Grande to work with park rangers to control the invasive grass, which is destroying the spiders’ habitats and help restore the original landscape.

Bristol Zoo Gardens is a conservation and education charity and relies on the generous support of the public, not only to fund its important work in the zoo but also its vital conservation and research projects spanning five continents.

For more information about visiting Bristol Zoo Gardens, visit their website at www.bristolzoo.org.uk .