August 21, 2015

By Bob Merz
Zoological Manager of Invertebrates

See updated story from about 2017 reintroduction.

Thirty years after going extinct in the wild, 429 Partula snails were returned home to the Papehue Valley on the Tahiti island of French Polynesia. These rare snails were raised in zoos across the world, and all were descendants of snails collected in this lush green valley in 1984, when three scientists realized that some of the species of Partula snails in that area had vanished.

The scientists put out a call to save the remaining species by breeding them in zoos. In 1988, the Saint Louis Zoo became a leader in creating a breeding plan to save these snails. This summer the Zoo contributed 140 individual snails to the shipment of 243 that went to London Zoo, where they received a thorough health screening, before being placed on a flight to Tahiti. The snails were greeted with fanfare and a ukulele tune as field scientists headed to a reserve, where from July 24 to Aug. 15, they carefully released and then began monitoring the survival rate of the snails.

Why should we care so much about a bland-colored creature that is not much bigger than a thumbnail and eats microscopic plants? It is tempting to deny the inherent value of any species by asking, “What good it is? What does it do? Would it matter much if it were gone?” Ultimately that is simply asking, “How does it impact us as humans?”

But zoom out just a little from this vantage point, and you can start to see that all species play roles in the ecosystems in which they live. They consume, they transport other organisms and nutrients, and they are consumed by other species. It’s a mind-bogglingly complex system. And the story of the Partula snail is one of drastic and direct human meddling with this system—to the point of the snail’s extinction in the wild.  

The snails’ demise began in the 1970s with the importation of African land snails as a food source. When the African land snail began eating local crops, another snail—the rosy wolf snail, a predator of other snails—was brought to the island to control it. However, these predator snails ate the Partula snails instead of the African land snails. By 1987, many species of Partula snails had gone extinct.  In the midst of impending and certain extinction, several remaining species were taken into captivity. An international collaboration of 14 zoos are now breeding the species, and approximately 1,900 Partula snails currently live at the Monsanto Insectarium of the Saint Louis Zoo.

I was particularly pleased to learn that of all the species shipped, our Zoo’s snails, the Partula nodosa, were the ones that fared best on the journey from London to Tahiti. It’s reassuring to know that some of those St. Louis-born snails are living back on the homeland of Tahiti in an area that has been free of the predator snails for over a decade. I am cautiously optimistic about the success of this test release. The hope is that this is truly an example of zoos serving as arks and that the snails will continue to thrive in the wild.

Category: Conservation
Tag: snails