Experience a Story of Survival

Nearly three decades ago, a tiny Tahitian land snail called the Partula nodosa was declared extinct in the wild – only 26 individual snails remained. In a final attempt to save the species from being completely wiped from the Earth, those 26 snails were sent to the Detroit Zoo as part of a cooperative breeding program.

Animal care staff worked carefully to provide the best possible living conditions for the snails while focusing on their successful reproduction, which eventually resulted in the rescue and recovery of the species. Thirty years later, there are now more than 6,000 individuals living in North American zoos, all descendants from the original group that came to the Detroit Zoo. In the last two years, 160 of these snails have been sent to Tahiti for reintroduction in the wild.

Visitors to the Detroit Zoo can become a part of this story at Shelle Isle, an exhibit in the Wildlife Interpretive Gallery that features the conservation story of these tiny mollusks. Guests are transported to the Tahitian rainforest, surrounded by tropical plants. A short video tells the snails’ story from a stable population in the first half of the 20th century to their sharp decline in the late 1970s, when an attempt to protect farmers’ crops from African land snails went awry and the Florida rosy wolf snails that were introduced to control the population preferred to eat the Partulid snails. The video also includes footage from the release of the Detroit-bred snails in Tahiti in 2015. Guests are invited to feel the shell of a giant replica of the Partula nodosa and more closely observe its structure and form. A second monitor has a live camera feed into the p. nodosa habitat in a behind-the-scenes area at the Detroit Zoo, giving guests a glimpse of the snails’ daily lives.

A favorite feature in this space is a large, “fallen” log where tiny, exact replica snails sit. Two magnifying glasses attached to the log allow visitors to get a close view of these tiny creatures. Many of them have a yellow number painted on their shell, which represents the way the snails are tagged by scientists before being released in Tahiti in order to monitor their movements and survival. The few that don’t have numbers painted on them are meant to demonstrate the successful reproduction in the wild that researchers have already observed, and the project’s continued success.

For us, an important part of this story is that it focuses not on a charismatic megavertebrate, but on a species that is not well-known, isn’t found on nursery walls or represented in the rows of stuffed animals on a toy store shelf. Conservation is not a beauty contest; all animals are important and the Detroit Zoological Society (DZS) works tirelessly to conserve species large and small – including the tiniest and slimiest of snails. By supporting the DZS, you are a critical part of this important work.

– Claire Lannoye Hall is a curator of education for the Detroit Zoological Society.

Notes from the Field: Detroit Zoo Continues to Save Once-Extinct Snail Species

The Detroit Zoological Society (DZS) is continuing to bolster the wild population of a species of Tahitian land snail called Partula nodosa, which we are credited with saving from extinction. At one point, all the P. nodosa in the world lived at the Detroit Zoo as part of a breeding program that began in 1989 after the species had been declared extinct in the wild. Last summer, 100 of these snails were carefully packaged before embarking on a journey to the tropical island of Tahiti. Last month, an additional 60 snails began their voyage, departing the Detroit Zoo on a path first to the Netherlands before their eventual release into the wilds of the South Pacific.

P. nodosa were once found across Tahiti and other south Pacific islands among more than 125 different species of land snails. These beautifully striped snails were important in the ceremonial jewelry and decorations of native islanders, and the snails served as an ideal study group to learn more about the evolution of diversity.

Much of the Partulid snail diversity was lost because of a botched attempt at what is known as “biological control”, or the control of a pest by the introduction of a natural enemy or predator. In 1967, giant African land snails were introduced to Tahiti and other south Pacific islands to serve as a source of protein for local people. However, some African snails escaped, bred very rapidly, and began eating farmers’ crops, threatening the local economy. To control the African snails, Florida rosy wolf snails were introduced a decade later, but the wolf snails preferred to eat the Partulid snails, which caused the extinction of many of the Partulid species.

For nearly three decades, the DZS has been breeding these snails in a behind-the-scenes area as part of a collaborative effort with other zoos. The project began in 1989 with 115 Tahitian land snails of five different species – while the DZS focused its efforts on P. nodosa, other zoos began working on the others. Our program led to the rescue and recovery of the species – currently there are 4,000 individuals living in North American zoos, all descendants from the Detroit Zoo’s original small group.

Paul Buzzard, Ph.D., is the Director of Conservation for the Detroit Zoological Society.

Amphibian Conservation: Wyoming Toads Prepare for Breeding

A pair of small gold eyes peers out from under a mass of sphagnum moss. In a day or two, this warty creature will complete its climb out from the depths of the sandy soil where he has spent the last 30 days sleeping and “chilling” at a cool 38 degrees. Along with seven other individuals of this species, he will awaken due to an increase in temperature and light. By the time the temperature reaches 74 degrees, he will have completely removed himself from the soil and be sitting atop it, hopefully alongside his companion, a slightly larger female. In the week that follows, events these two small cold-blooded creatures will go through could lead to producing thousands of their species in a matter of hours due to their “explosive” nature.

The Wyoming toad (Anaxyrus baxteri) is one of North America’s most endangered species and one of the amphibians we work with as part of a Species Survival Plan (SSP) at the Detroit Zoo’s National Amphibian Conservation Center.  This toad’s wild populations began declining in the 1970s, and by the 1980s was listed as an Endangered Species by the International Union for the Conservation of Nature (IUCN). Possible causes for the population decline are use of aerial pesticides to eliminate mosquitoes, habitat manipulation, and disease in the form of the amphibian chytrid fungus. Realizing a decline was occurring, the last remaining toads were collected and by 1994, all remaining wild-born Wyoming toads were believed to be entirely in captivity. The IUCN now describes the Wyoming toad as extinct in the wild, meaning any toad currently found in the wild has come from captive breeding, in which the Detroit Zoological Society (DZS) has been actively involved.

The Wyoming toad SSP is managed by the Association of Zoos and Aquariums (AZA). The DZS has been a member of this conservation program since 1995 and since 2001 has sent a total of 6,505 tadpoles and toadlets to the wild. All Wyoming toads are the responsibility of the U.S. Fish and Wildlife Service (USFWS), so members of the AZA work closely with them to follow all USFWS permit guidelines for keeping them in captivity. The goal of any captive breeding program is to produce healthy offspring for release into the wild with the goal of rebuilding them into a self-sustaining population. Each toad in captivity is identified and tracked, which helps to pair toads that will produce the most genetically diverse and healthy offspring. Breeding pairs of toads are chosen almost a year in advance so toads have plenty of time to move from one zoo to another to create the breeding pairs.

Although not as well known as Jabari and Kivuli, the giraffe couple at the Detroit Zoo, Wyoming toads Butler and Beverly are a very important couple of toads. They are part of a “bio-secure” population and will never be seen by the public, which ensures they will not accidentally release diseases, known or unknown, into the wild via their offspring. They are held with four other pairs of Wyoming toads in a special room away from all other amphibians, so they will remain free of diseases that could otherwise be found in species not native to the western region of North America.

At the AZA’s recommendation, Butler arrived at the Detroit Zoo last October to be paired with Beverly, who arrived in 2012. Both are now 3 years old, which is about middle aged for a Wyoming toad. In early April, they were placed together into a thermostat-controlled “hibernaculum”, which is used to cool the toads, simulating the hibernation period a wild Wyoming toad would go through during the winter. The toads are kept cooled for about a month to help prepare them for breeding; eggs or sperms may develop and mature as a result of this cooling. The toads are given plenty of sandy soil to bury down into and sleep in just as they would have in the wild, and the Zoo’s animal care staff checks in on them weekly to make sure they are doing well.

At the end of May, the temperature in the hibernaculum will be increased to 70 degrees Fahrenheit and the toads will begin to awaken. Once they have climbed out from the soil, we will place them back into regular husbandry for a few days where they will continue to warm up and eat. Recordings of male toads calling are played during this time to condition toads further for breeding. Within a few days of emerging from hibernation, Butler and Beverly will be placed into a breeding chamber with 2-3 inches of water. The pair will hopefully go into “amplexus” within a few hours, which happens when the male positions himself on top of the female using his front legs and squeezes her, encouraging her to lay eggs. He fertilizes the eggs as she lays them, usually in the dark, overnight. Butler and Beverly should lay thousands of eggs, which is typical of toad species. Described as “explosive breeders”, the more eggs they can lay the better the chance offspring have of surviving the elements, diseases and predators. Since this is a captive breeding, we can help the thousands of eggs that Butler and Beverly produce survive into strong, healthy tadpoles.

Approximately two to three weeks after eggs have hatched into thousands of hungry tadpoles, arrangements are made with the USFWS to ship the tadpoles to Wyoming, where they will be released into protected wetlands. These tadpoles will add to those previously produced in captivity sent yearly by the zoos that participate in this program and the USFWS.

The wetlands are monitored during the spring and summer as part of yearly field surveys done to track the health and population of the toads. This year we hope that Butler, Beverly and the three other pairs of Wyoming toads at the Detroit Zoo are able to contribute thousands of healthy tadpoles to the wild population.

– Rebecca Johnson is the associate curator of amphibians for the Detroit Zoological Society.