Manus Green Tree Snail

Background - The Manus green tree snail (Papustyla pulcherrima) is found only on Manus Island, a moderate sized 100 km long, densely forested island to the north of Papua New Guinea. The Manus green snail is iconic of the island and is heavily featured in the ceremonial dress of Manusians, appears on the provincial flag and is also sold as jewellery. Its shell is renowned for its beauty. 

The shell is conical, emerald green in colour with a fine yellow border to the whorl, and a white lip. It grows ~4 cm in total length. While most conservation attention is focused on large charismatic vertebrates, invertebrates globally receive little if any attention - the Manus green tree snail is no different, and is currently classified in the IUCN redlist as Data Deficient but appears listed on the US Endangered Species Act. Conservation Initiatives -  WCS’s program of work on the Manus green tree snail comes as part of our ongoing research into the links between culture and nature in Papua New Guinea supported by the Christensen  Fund. 

By virtue of Manus’s widespread population living in and off the wild landscape there exists a vast library of traditional and local ecological knowledge residing within the everyday population. Increasingly researchers have been suggesting the potential to harness this kind of knowledge to answer fundamental questions regarding natural resources in data-poor situations. WCS has tapped this knowledge using a technique known as “wisdom-of-the-crowds” by interviewing over 400 Manusians and mathematically aggregating their knowledge. 

As a result we have been able to construct a species abundance map for much of the island. Our research suggests that there are only two main risks to the sustainability of this species: habitat destruction and over collection. Large-scale habitat destruction caused by logging appears to be the greatest threat, with the expected loss of the snails being directly proportional to the amount of forest removed. The stronghold of the snails is in the central Manus forest, an area in which WCS is already working with communities to actively protect the forest via a REDD+ initiative. 

Over-collection for customary purposes or food is much less of a threat. However, from our interviews, we became aware of international trafficking of the shells which is currently prohibited by CITES (Convention on International Trade in Endangered Species). Snail shells have been advertised online in Australia for more than AUD$250. Given that shells are sold for 1 Kina (~AUD$0.50) in the Lorengau market, there is the potential for a dramatic increase in price which could fuel harvesting at unsustainable levels. The WCS strategy will be to launch a media campaign reminding Manusians of the special iconic nature of the snail, the illegality of international trafficking, and the potential penalties. WCS will also be liaising with PNG and Australian Customs authorities to inform them of the illicit trade.

The Christensen Foundation
Nathan Whitmore
Scientific Support Officer

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