Dominica’s great frog rescue

When a deadly fungus threatened to wipe out the Mountain Chicken in Dominica, researchers came up with a daring rescue plan

Members of the project team check released frogs for signs of the chytrid. Photograph courtesy the Mountain Chicken Recovery ProjectThe frogs were transported back to Montserrat in specially designed crates. Photograph courtesy the Mountain Chicken Recovery ProjectThirty-three frogs bred in captivity were released in Montserrat’s Soufrière Hills. Photograph courtesy the Mountain Chicken Recovery Project

Leptodactylus fallax was always going to have it rough. Of all the places on the planet for this giant frog to call home, it picked the Caribbean. Caribbean people love chicken, and, unfortunately, the Giant Ditch Frog’s hind legs look — and taste — like juicy drumsticks. The corpulent “crapaud” (as frogs are known around the region) was duly christened the Mountain Chicken, and promptly fried, dipped in gravy, and served with yam.

Over the decades, the culinary cull — estimated at anywhere between eight thousand and thirty-six thousand frogs each year — whittled away the population of Mountain Chickens on the last two Caribbean islands on which they could be found, Dominica and Montserrat. Then in 1995 the Soufrière Hills volcano in Montserrat erupted, and three quarters of the island was engulfed in lava and ash. Much of the frog’s rainforest habitat and the insect population on which it fed were destroyed.

In a prescient move, the Durrell Wildlife Conservation Trust, a UK-based group whose mission is to save species from extinction, rescued thirteen frogs in 1999 from their still-smouldering habitat, in the hope of breeding a “safety-net” population. “It’s such an iconic species, says Andrew Terry, head of field programmes at the Durrell Trust. “It’s the top native predator on these islands. And it’s one of the largest frogs in the world. It would be such a tragedy to lose this animal. It would be gone forever.”

Three years later, the global crisis affecting amphibian species finally struck Dominica’s “national dish.” Mountain Chickens began dying by the dozen. The cause? Chytridiomycosis. First identified in Australia in 1993, the infectious fungal disease has been decimating amphibian species around the world. The fungus affects the outermost layers of the skin, preventing the accumulation of keratin, which causes the skin to thicken and become less permeable to fluids and salts, effectively starving the animal of oxygen.

Globally, more than 120 amphibian species have become extinct since 1980. Forty-three per cent of all known amphibian species are declining, and nearly a third — almost 1,900 — are now threatened with extinction. Compared to other regions, the Caribbean has the highest percentage of threatened amphibians, with almost three quarters of all species in the region under threat — from not just the deadly chytrid, but also habitat loss and degradation, pollutants, and invasive species (rats, cats, feral pigs, etc).

Within two years of chytridiomycosis hitting Dominica, the Mountain Chicken population declined by eighty per cent. Efforts were made to prevent its spread to Montserrat, but in February 2009 the first cases of infected frogs were discovered there. Within a few months, eighty to ninety per cent of the Mountain Chicken population in Montserrat was dead. By July of that year, chytridiomycosis had been confirmed in the last healthy population of Montserratian Mountain Chickens. The species was deemed critically endangered.

In stepped the Durrell Wildlife Conservation Trust, which quickly spearheaded the setting up of a Mountain Chicken Recovery Programme, along with the Zoological Society of London, the North of England Zoological Society (Chester Zoo), and the Parken Zoo in Sweden, in collaboration with the governments of Montserrat and Dominica. They sent a team of herpetological and veterinary experts to Montserrat to assess the damage and to train local forestry staff in bio-security techniques to limit the spread of the fungus. A healthy population of Mountain Chickens was discovered in an isolated mountainous area called Fairy Walk. Fifty mountain chickens were rescued and flown to Europe, housed in specialist temperature-controlled boxes that reduced stress and protected the frogs.

Twelve were sent to Durrell’s headquarters in Jersey, twelve to London Zoo, and twenty-six to Parken Zoo. They were kept in bio-secure conditions to minimise the risk of disease transmission. In August last year, two of the females at London Zoo delivered massive broods, totalling seventy-six live offspring. Researchers captured footage of a mother feeding the tadpoles her unfertilised eggs. This magical moment, a sight rarely seen by humans, was filmed for the first time, and featured in a documentary series about London Zoo. At Parken Zoo, meanwhile, the conservation team went one step further, and used modeller’s clay to create faux nest burrows similar to the ones the frogs would have made in the forest floor.

In January 2011, thirty-three healthy frogs were released in the south Soufrière Hills of Montserrat, part of the volcano exclusion zone, which was free of the fungus. The frogs were fitted with microchips which allow easy tracking with radio transmitters. Since then, another batch has been released into the wild. The conservation team continuously collects data from the frogs. Swabs are done of their skin to test for chytridiomycosis, and signs that they might be breeding.

On both islands, breeding facilities have been set up to boost the populations. To get the frogs into breeding condition, they have been placed in the fake burrows designed by Parken Zoo and extra food has been laid on (in Montserrat, the zoologists are also breeding the “food” — i.e., cockroaches, three species of crickets, snails, and slugs). A sprinkler system has been set up to keep the frogs happy and hydrated.

Some of the released frogs have succumbed to chytridiomycosis, which was expected, and may actually help scientists to better understand the ecology and life cycle of the deadly fungus. “All the information we’ve collected was previously unknown for Mountain Chicken, and will help us understand the processes that are going on, so that we are able to make informed decisions on how to manage the species,” project co-ordinator Sarah-Louise Adams told BBC Nature. “This is a global issue,” adds Andrew Terry, “because one third of all amphibian species around the world are being affected by the chytrid. There’s a real and urgent need to contain this disease, because it’s transmitted so easily.”

“The Mountain Chicken is one of the best cases to study for this reason,” he continues. “It’s helping us to understand how the disease works. It is serving an immediate global role in helping us to fight this disease.” There’s still a long way to go with the research, and full recovery of the Caribbean’s Mountain Chicken population. But there’s also great hope that they may yet yield the answers to save the rest of the world’s amphibians.