The two female mountain chicken frogs responsible for the 76 new additions are part of an attempt to rescue the species from extinction.
All 12 frogs in the UK breeding programme came from Montserrat, where the chytrid fungus has ravaged the population.
“We’re absolutely chuffed to bits,” said herpetologist, Dr Ian Stephen.
The frogs, simply known as mountain chickens, were rescued as part of the conservation efforts led by the Zoological Society of London (ZSL) and the Durrell Wildlife Conservation Trust (DWCT).
“The first challenge was getting them out of the Caribbean in to Europe safely,” said Dr Ian Stephen, ZSL’s Curator of Herpetology.
The frogs were transported in temperature-controlled boxes to protect them and minimise stress on the long and hazardous journey.
“Although the mountain chicken is one of the biggest frogs in the world they’re still a small animal so they’re incredibly sensitive to temperature fluctuations and that tends to be the thing that would kill a frog during transportation.”
The 50 airlifted frogs were split into three groups and housed at ZSL London Zoo, the DWCT in Jersey and at Parken Zoo in Sweden in the hope of growing a healthy population of the species.
Since their arrival, the 12 UK frogs have been living in a bio-secure breeding unit at the zoo, where the eggs were laid.
Mountain chicken females produce a special foam nest into which they lay their eggs. The tadpoles then feed on deliberately unfertilised eggs laid by the female.
Dr Stephen hopes that most of the 76 will survive to adulthood and make a return trip to the Caribbean.
“Because a mountain chicken wouldn’t lay hundreds or thousands of eggs like a common frog would in England, for the ones that make it to metamorphosis, you’d hope for a very high success rate.”
The mountain chicken tadpoles were fed unfertilised eggs every few days
On Montserrat, mountain chicken frogs face threats from volcanic activity and predation but the biggest threat remains the chytrid fungus.
“It’s an incredibly important disease because it’s probably the first time where a disease is affecting an entire class of animals.”
“It’s moving towards driving the extinction of most of the amphibian species across the globe,” Dr Stephen told BBC Nature.