Spiders, Snails and Other Conservation Tales
Whenever you think of wildlife conservation, it tends to be the higher and larger vertebrates that grab the limelight. This isn’t such a bad thing as it is often the case that by conserving the larger animals in their environment that you’re also conserving the myriad of plant and animal life that share and support their environment. An exception to this generalisation can be found on small remote islands such as the Pacific islands of Southern Polynesia.
Prior to human interventions, life on small remote volcanic islands had first arrived on the wind, by sea or by flight, before settling and evolving for between half a million and a million years ago. The Partula Snail is unique to the Southern Polynesia, but by the end of the 20th century, the number of species of Partula surviving had fallen from 61 to just 5 . This catastrophic decline only began in the late 20th century. As befits an island species with few natural predators, the Partula has a low reproductive rate, so recovery from introduced predators is not going to be enough without outside interventions.
The first threat to the Partulas was the African giant land snail (Achatina fulica) which was initially introduced to stock snail farms for the food trade. However, these snails didn’t suit the local palette and the imported snails escaped from farms some of which were simply abandoned. The African giant land snail, which had no endemic predators, became a predator of the Partulas. This introduction by human neglect was then further compounded by the subsequent misguided introduction of the Cannibal snail (Euglandina rosea) from North America , so called because it predates on other snail species. The introduction’s aim was to eradicate the African giant land snail – but the Cannibal snail didn’t discriminate when it came to the endemic Partulas.
The zoo community has responded with a captive ex-situ breeding programme and support for in-situ conservation. Led by ZSL (London Zoo) and supported by 14 other zoos, including Durrell Wildlife Conservation Trust, Martin Mere Wildfowl Trust, Edinburgh Zoo, Bristol Zoo, Chester Zoo, Thoiry Zoo, Riga Zoo, Poznan Zoo, St. Louis Zoo, Atlanta Zoo, Detroit Zoo, Woodland Park Zoo and the Virginia University. A re-introduction programme is underway in predator –free reserves. So far so good and an eco-system is on its way to being restored.
Conservation isn’t restricted to far-away and exotic places; it can be on our own doorstep in the UK. Take the Fen raft spider (Dolomedes plantarius) a denizen of the wetlands and fens and restricted to 3 areas of East Anglia, East Sussex and South Wales . For a spider that depends upon a permanent supply of clean, still or slow moving water; habitat pollution, or in worst case, habitat loss could have led to the extinction of one of Britain’s rarest and biggest spider – it has a 10cm leg span! Fen spiders do not easily spread out into new areas and would need a helping hand from a range of conservation organisations. UK Zoos have been charged with a captive breeding programme, whilst wildlife organisations have managed and monitored their re-introduction. One of the zoos in the breeding programme is Chester, where hundreds of the UK’s rarest spiders are being reared at Chester Zoo ahead of their release into the wild. 400 fen raft spiderlings were hand-reared for two months in a purpose-built, bio-secure pod at the zoo. The spiders were a kept in separate test tubes so they didn’t eat each other and were individually hand feed with fruit flies.
So whilst it’s the mega fauna that attracts the majority of the media’s attention and conservation funding, it should be remembered that the littler creatures that fill important ecological niches also deserve the support and intervention of conservation organisations, with zoos uniquely placed to apply their experience of breeding and rearing animals great and small
David Lomas, 2014
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