Four species of snail thought to be extinct have been found on a small Atlantic island. After more than 100 years without a confirmed observation, the species were rediscovered on Deserta Grande by the local conservationists at IFCN. Their only home and habitat had been devastated by invasive species so their reappearance comes as a very pleasant surprise.
However, initial estimates of their numbers (less than 50) suggest they may be on the verge of extinction.
For this project, we have joined a hopeful rescue operation led by the IFCN that aims to ensure the long term survival of these species.
The plan involves starting a captive breeding programme in collaboration with Chester Zoo and Bristol Zoo to boost snail numbers. But the first step of finding enough individuals of these endangered animals, perched on this rugged and remote island, was no easy feat. This is why we sent Tiago, one of our adventurous conservation biologists, to navigate the perilous rocky terrain and help with the expedition work.
Once there are enough snails in captivity, we’ll be exploring the possibility of reintroducing them onto an adjacent island where the fossil record suggests the species used to be abundant and where the habitat is recovering following the eradication of invasive species.
For this project we are contributing to the fieldwork required to prevent the extinction of four species of snail that are endemic to Deserta grande, an island of the Madeira archipelago in the middle of the Atlantic ocean. All four species are deemed critically endangered according to IUCN criteria.
The main threat for these snails have been the invasive species that have raised havoc on the island’s fragile ecosystem after being introduced by humans settlers. Goats have proliferated and decimated the native vegetation and accelerated soil erosion. While direct threats come from mice, who feed on the snails and the seeds of native plants.
This rescue operation involves multiple expeditions to:
- collect enough individuals from each species to start a captive breeding programme,
- monitor the remaining populations to obtain more accurate estimates of population size, population trends and threats,
- collect field environmental data to inform the conditions for captive breeding and the search for suitable reintroduction sites.
Each expedition entails some complicated boat disembarkation, strenuous hikes over steep terrain and long hours spent searching for snails under rocks and vegetation. Tiago, one of our Conservation biologists is joining these efforts to help with the surveys, to carry out the drone mapping and to document the expeditions. With the help of our members we have also been able to fund essential equipment to continue the fieldwork including items such as:
- data loggers and sensors to monitor environmental conditions at the sites of the last remaining populations,
- sieves for more effective sampling of soil and soil dwelling animals,
- tagging materials to be used for population monitoring.
The short-term goal of the rescue operation is to prevent the imminent extinction of these unique species. The long-term goal is to boost snail numbers and carry out reintroductions in suitable locations where the original threats have been dealt with and where the snails can thrive without further intervention. The project should also provide an example for future snail conservation work, which is much needed around the world right now.
Learn More About the Context Behind this Project
Sadly, these special species are going extinct and not at a snail’s pace, quite the opposite.
Why are these Species Important?
Although many people feel sad and worried about the news that we are at the start of a human induced mass extinction, few have a clear picture of what species we are actually losing. If you look at all the recorded animal extinctions since the year 1500 you will find that 40% of them are land or freshwater snail species and most have occurred on oceanic islands. We find this astonishing and alarming!
Two main factors are thought to explain this:
- Many oceanic snail species have very narrow ranges and even small amounts of habitat loss or degradation can tip them to extinction.
- Most of these species had evolved under low predation pressure so were susceptible to being wiped out by invasive species for which they had evolved no defence mechanisms.
Although snails may not receive the same attention as charismatic birds or mammals, they are unique and have their own evolutionary history and adaptations that are worth protecting.
Land snails are also valuable for a few other reasons. By feeding on dead vegetation they help with nutrient cycling and maintaining soil fertility and they also provide food for other small animals. Some species are fairly sensitive to habitat degradation so can be useful as bioindicator species serving as an early warning system for the ecosystem.
Finally, because of their limited dispersal ability and high species diversity they are a great study subject to understand:
- how evolution happens,
- how species emerge and,
- how they are lost to extinction.
Snails can also be identified from their shells after death and in the fossil record making them particularly suitable subjects for this interesting and consequential area of research.
More Reasons Why They Need Protecting
The Madeira archipelago is a hotspot for snail biodiversity
The situation in Madeira is fairly representative of the problems facing the land snails of oceanic islands worldwide. There are close to 320 known species of land snail in the archipelago of Madeira making it a snail biodiversity hotspot. Approximately 80% of these are endemic meaning they are found nowhere else in the world. On Deserta grande, the island we are focusing on for this project, there are
Lazarus taxa species rediscovered out of extinction
Lazarus taxa species are those that were rediscovered after they were thought to be extinct. For years, Isamberto Silva and Dinarte Teixeira from the IFCN had seen the fossils of these four species throughout the island. For them, finally seeing a live specimen after only finding their fossils was like seeing a dinosaur in the flesh having only imagined their colors, anatomy and behaviour. Initial population estimates suggested there may be less than 50 individuals left of each species so it became clear that a rescue operation was needed.
Once again we thank our members for supporting projects like this one. Every Mossy Earth member is helping to restore neglected species, such as these snails, whose current state is a shell of their former self.
This snail species rescue operation is led by Dinarte Teixeira, the Malacologist at IFCN who sounded the alarm about these species. The captive breeding programme is led by Chester Zoo and Bristol Zoo Gardens. The project is also integrated into a broader conservation strategy of the IUCN’S Mid Atlantic Islands Species Specialist Group (http://www.maiisg.com/).
Sources & further reading
- “Evolution and Extinction of Land Snails on Oceanic Islands” - Annual Review of Ecology, Evolution, and Systematics
- “Snails Are Going Extinct: Here's Why That Matters” - Scientific American