Homecoming! A journey from stress to success for Norfolk Island snails

It’s been five years since Norfolk Island local, Mark Scott, showed Malacologists from the Australian Museum a small living population of a snail species previously feared to be extinct. Now, after a successful ex situ captive breeding program at Taronga Zoo founded with just 46 snails, scientists are bringing their descendants back home to Norfolk Island.

Advena campbellii, or Campbell’s keeled glass-snail, is likely to have once been widespread on Norfolk Island. The current population is limited to a single catchment area in the Norfolk Island National Park (NINP), and this makes it vulnerable to extinction. We are planning to introduce zoo-bred snails into three additional sites in the National Park, which, if successful, would greatly increase this species’ robustness and long-term chances of survival in the wild.

There have been very few land snail introductions worldwide, and this is the first of its kind in Australia. We have interviewed snail translocation experts from around the world to develop a detailed plan. But we also need to acknowledge that there is a risk of failure because each snail species is unique and they may differ in their response to translocations. We hope to mitigate this with in-depth knowledge of the snails built up over the past five years, detailed planning, a strong team with varied expertise (from the NINP, Taronga Zoo, Western Sydney University and the Australian Museum), and international advisors.

The journey to this point has not always been straightforward. For the first few years, the zoo population remained small, despite all the care of the husbandry team. However, gradually over time the team made improvements in the husbandry conditions with a very positive impact on snail health and population size. And slowly a picture has emerged: these snails are extremely sensitive to stress.

So, what stresses a snail? Well, abrupt changes to diet, excessive disturbance or handling, and transport between two different environments all seem to cause undue stress in our snails, impacting fertility and longevity. So that begs the question: how do we move hundreds of snails that are sensitive to change to a new environment, with minimal impact? I can tell you, a LOT of thought has been put into the answer!

We have elected to transport our snails in the tanks they live in, rather than repackaging for transport. We are also establishing a snail facility at the NINP headquarters where the snails will live for several weeks after their move to the island, to allow them to acclimatise. During this time a Taronga Zoo husbandry expert will slowly introduce a natural diet and monitor for signs of stress and will train the NINP staff in caring for snails and understanding their behaviour. When the snails are ready, they will be released into the wild and NINP staff and other team members will follow up with monitoring to track their progress.

We cannot remove all stress from the translocation for the snails. But on the other hand, it doesn’t make sense to leave them in the zoo when the wild population on Norfolk Island would benefit so greatly from an increase in numbers. We acknowledge that the reintroduction is a risk, but it’s a well-considered one.

And just in case you were wondering: the incoming snails will not be making an appearance in veggie gardens. Norfolk Island’s native snails are primarily found in relatively undisturbed native habitat, and even if one makes its way to a garden, it won’t be munching on vegetables – the true culprits are introduced species from Europe, Asia and Africa that are common garden pests worldwide.

Watch this space for more updates, as the snails adjust to being home again!