A species of tropical tree snail is no longer extinct in the wild following a successful reintroduction project.

A global conservation effort to reintroduce a tiny snail to the wild is celebrating a momentous milestone: for the first time in 40 years, conservationists have found born-in-the-wild adult Partula tohiveana—meaning the precious mollusks have successfully established themselves in French Polynesia.

This year Cambridge’s Dr. Justin Gerlach helped restore more than 6,000 of the snails to Moorea, their French Polynesian island home as part of an annual reintroduction of zoo-bred “Extinct in the Wild” and “Critically Endangered” snail species—carried out through collaboration with zoos around the world.

During their work, the team found unmarked Partula tohiveana: proof that previously reintroduced snails have successfully bred in the area.

The momentous discovery means Partula tohiveana can now be considered as established—an incredibly rewarding result for 40 years of dedication and collaboration. Conservationists will now begin the process of downlisting the snails from “Extinct-in-the-Wild” to “Critically Endangered” on the IUCN’s Red List.

Very few species have been reintroduced successfully after having been completely extinct in the wild. This is also the very first invertebrate species where this has been achieved.

Ten species and sub-species of the tropical snails, reared at London Zoo, Bristol Zoological Society, Detroit Zoological Society, Marwell Wildlife, the Royal Zoological Society of Scotland, Saint Louis Zoo, Sedgwick County Zoo, Woodland Park Zoo and Zoo Schwerin, traveled more than 15,000 km to Tahiti at the beginning of September.

Before making the two-day journey to the islands of Tahiti, Moorea and Huahine, the incredibly rare snails, which each measure a tiny 1–2 cm in length, were individually counted and marked with a dot of red UV reflective paint. The “snail varnish” glows under UV torchlight, helping conservationists in the field to spot and monitor the nocturnal snails at night, when they’re most active.

London Zoo’s Senior Curator of Invertebrates, Paul Pearce-Kelly, who leads the Partula conservation program, said, “Though little, these snails have great cultural, scientific and conservation value. Partula snails have always been part of Polynesia’s rich cultural heritage and play an important role in the ecological health of their forest habitats.

“They’ve also been studied for over a century for the insights they give into how species evolve in isolated environments. Most recently, they’re providing a valuable conservation model for helping hundreds of endangered island species.”

He added, “This collaborative conservation effort is playing a crucial role in saving these species from extinction. It’s a powerful example of how conservation zoos can combat biodiversity loss. At a time when nature faces unprecedented challenges, these small snails are a symbol of hope for global wildlife.”

Partula snails—also known as Polynesian tree snails—eat decaying plant tissue and fungi, so they play an important role in maintaining forest health. Returning these rare snails back to the wild helps to restore the ecological balance in these islands.

Dr. Gerlach of Peterhouse, University of Cambridge and an Academic Associate at the University’s Museum of Zoology, said, “Discovering wild-born adult snails was a great moment. Very few animal species have been re-established back in the wild, so this is a fantastic achievement for the program—the fruit of a vast amount of work.”

Conservation zoos are working with the French Polynesian Government’s Direction de l’environnement, to save Partula snails from extinction. In the 1980s and early 1990s, these snails faced a critical threat after the invasive rosy wolf snail (Euglandina rosea) was introduced to control the African giant land snail (Lissachatina fulica).

Unfortunately, the predatory species targeted the native snails instead, leading to the extinction or near-extinction of many Partula species across the region.

In the early 1990s, the last remaining individuals of several Partula species were rescued by London and Edinburgh Zoos, launching an international conservation breeding program. This collaboration between 15 zoos cares for 15 species and subspecies, most of which are classified as “Extinct-in-the-Wild.”

These rescued snails, along with those already being studied at universities in the U.K. and North America, became the foundation for reintroducing the species back onto their native island homes.

Paul said, “After decades of caring for these species in conservation zoos and working with the Direction de l’environnement to prepare the islands, we started reintroducing Partula snails back into their lowland tropical forests almost 10 years ago.

Since then, we’ve reintroduced over 30,000 snails, including 10 Extinct-in-the-Wild species and subspecies, with this year’s release being the largest so far, thanks to our international team and collaborators, including mollusk specialist Dr. Justin Gerlach of Peterhouse, University of Cambridge.”

A rescue effort can take many forms—a life raft, a firehose, an airlift. For animals whose populations are in decline from inbreeding, genetics itself can be a lifesaver.

Genomic research led by the University of California, Davis, reveals clues about montane red foxes‘ distant past that may prove critical to their future survival. The study, published in the journal Molecular Biology and Evolution, examines the potential for genetic rescue to help restore populations of these mountain-dwelling red foxes. The research is especially relevant for the estimated 30 or fewer native red foxes living in the Lassen Peak region of California.

The study found that inbreeding is impacting the Lassen red fox population. Thousands of years ago—long before unregulated trapping and poison knocked back their populations in the 1890s and early 1900s—red foxes were not only abundant in these mountains, they were also more connected to neighboring foxes in Oregon, the Rocky Mountains and Washington Cascades than they are today. This positions them well for genetic rescue should managers decide to pursue it and reconnect the populations.

“Nothing we found disqualifies red foxes from genetic rescue,” said lead author Cate Quinn, who conducted the research as a UC Davis postdoctoral researcher with the Mammalian Ecology and Conservation Unit within the School of Veterinary Medicine. She is now a research biologist with the USDA Forest Service Rocky Mountain Research Station. “The study suggests that genetic rescue could be a viable option for the Lassen population.”

Rescue workers

Genetic rescue is a conservation tool to reverse the effects of inbreeding depression, which is when inbreeding reduces an animal’s fitness and ability to reproduce. Genetic rescue involves bringing new individuals to a population to introduce genetic variation and spur growth.

The tool is not considered lightly, and managers first must understand the severity of inbreeding, the historical baseline genetic rescue seeks to restore, and the deeper evolutionary relationships the foxes share with each other.

To fill those knowledge gaps, the scientists sequenced 28 whole genomes from the four subspecies of montane red foxes. These include small, isolated populations in the Pacific mountains, Oregon Cascades, Lassen Cascades and the Sierra Nevada, as well as a larger population in the Rocky Mountains and a subspecies in the Sacramento Valley. Using genomic technology, the authors could peer back in time to see if a population was always isolated, to what extent, and when that began to change.

Abundant, connected and diverse

The study found high levels of recent inbreeding in Lassen and Sierra Nevada red fox populations, with the Lassen red foxes a high priority for intervention. Only one montane red fox is known to have entered the Lassen population in more than 20 years of monitoring, the study said.

The data also revealed that 10,000 to 12,000 years ago, montane red foxes in the Western United States were abundant, connected and genetically diverse. The Lassen population was likely connected to the Oregon red foxes within the last century, breaking from each other relatively recently, Quinn said.

A hopeful way forward

Combined, these findings point to a hopeful way forward for Lassen’s red foxes, and for other red foxes facing similar challenges.

“We think trapping drove their population down, but we didn’t know what was keeping them small,” said senior author Ben Sacks, director of the Mammalian and Ecology Conservation Unit at the UC Davis School of Veterinary Medicine. “Now we see that what kept them small appears to be inbreeding depression. If what drove their decline is gone, can we bring them back? There is hope here.”

Quinn agrees, “Not too long ago, this was an abundant, connected, diverse population. That diversity still exists. If we were to restore them as a group, these foxes may still have a lot of adaptive potential.”

She cautions, however, that true genetic “rescue” requires reconnecting the whole subspecies—not just growing one population.

“If we only consider each small pocket individually, they’re in trouble, but if we look at the whole montane system, restoration is still possible,” Quinn said.

Additional co-authors include Sophie Preckler-Quisquater of UC Davis and Michael Buchalski of the California Department of Fish and Wildlife.