Flax snail  (Placostylus ambagiosus)

Classified as Vulnerable (VU) on the IUCN Red List 2007.

Flax snails (Placostylus spp.) are endemic to New Zealand and belong to the world’s oldest land snail family, which originated 200 to 300 million years ago (3). The long, coiled, shiny brown shell of this particular flax snail species can reach up to an impressive 9.4 centimetres (2) (4). Sadly, the beauty of their shells was fatal for many flax snail species, before shell collecting became illegal in 1982 (5).

Confined to the Te Paki Ecological Region in the far north of Northland, New Zealand (2) (6).

Flax snails generally inhabit coastal broadleaf forest and scrub, residing in pockets of leaf-litter on the ground (2) (4). Young flax snails live on the leaves in the tree canopy, only coming to live on the ground when they have grown sufficiently large (4) (6).

These nocturnal snails hide in the leaf litter during the day and come out at night to feed on fallen leaves (4).

Mating in flax snails appears to be triggered by rainfall and probably occurs every year, except in periods of drought. These snails may mate several times with several different partners. In a different flax snail species, egg-laying has been observed between November and February, with 20 to 30 eggs laid in a shallow nest in loose earth. Nests containing 30 or more eggs are thought to be the result of more than one snail laying in the same nest (6). While adult flax snails tend to stay in and around a relatively small area, the juveniles disperse widely (7). These flax snails reach maturity at three to five years of age and may live for over 20 years (6).

Like other large flax snails, this species has been badly affected by mammalian predators introduced to New Zealand, such as rodents, pigs, hedgehogs and possums (6). Habitat destruction and modification wrought by human settlers and the domestic and feral animals they brought has also had a dramatic and devastating impact on flax snail numbers, with sheep, cattle, horses, goats and pigs grazing, browsing and trampling vegetation (2) (6). As a result, this species, like many other flax snails, now survives only in a small reserve where it is protected and where the predators are controlled (4).

Management of the main flax snail colonies has existed since the early 1980s, mostly through poisoning rodent predators, enhancement planting, fencing colonies and stock control (2). Shell collecting became illegal in 1982 (5), and all Placostylus species have the status of Nationally Threatened Invertebrates, and as such are protected and intensively studied by the New Zealand Department of Conservation (4). New Zealand’s Department of Conservation also created a Giant Land Snail Recovery Plan in 1995, which has since been updated, and aims to prevent extinction and focus management towards the most genetically diverse populations (2).

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on flax snails and their conservation see:

• Parrish, R., Sherley, G. and Aviss, M. (1995) Giant Land Snail Recovery Plan Placostylu spp., Paryphanta sp. – Threatened Species Recovery Plan Series No. 13. Department of Conservation, Threatened Species Unit, Wellington, New Zealand. Available at:
  http://www.doc.govt.nz/upload/documents/science-and-technical/TSRP13.pdf