Olaf grasps Diane Barber’s gloved hands with his sticky, four-fingered legs. His skin is bumpy and moist, the colour of pebbles at the bottom of a river when dappled sun hits them. Olaf’s eyes are deep amber. His body lifts and falls with each breath. “The males get really pretty,” says Barber, ectotherms curator at Fort Worth zoo in Texas. “Sometimes they’ll turn a solid yellow when they’re in breeding form.”
In some ways, this toad shouldn’t exist at all. He is the progeny of an egg from a captive mother and sperm from a wild father – a hybrid from parents who were both dead. Olaf is not the first amphibian to be born via IVF – that has been happening for years – but he is the first to be born from sperm that was frozen and thawed.
“We were able to recover a genetic lineage that had disappeared, so we were able to produce an offspring from dead parents,” says Andy Kouba, an ecologist at Mississippi State University, who assisted with the project. “So that was an exciting first, to reintroduce genetic lines back into the population.”
Scientists have a lot of tools to conserve species, says Kouba, but they still need to hedge against extinction in the wild. One way could be to bank the genetic lineages of species by freezing sperm and egg deposits and then later thawing and combining them in a dish to create offspring.
Amphibians are at the forefront of an uphill battle against extinction, losing a greater proportion of species than any other vertebrate group. The IUCN estimates that at least 41% of amphibians are at imminent risk of extinction. Habitat loss, climate crisis and a fungal disease all play a role in their demise.
But amphibians are not the only species that can benefit from new technologies. In vitro fertilisation, hormone therapy and cryopreservation are increasingly being used as tools for conservation – for amphibians and beyond. In a fast-changing world, frozen zoos may be the places where tissues are kept, in the hope of boosting numbers or resurrecting species in the future.