In one final heroic stunt, as Valentine’s Day approached last year, Romeo’s keepers posted his profile on the dating site Match.com, bringing a flood of donations to fund one more expedition in search of wild water frogs. In January, the museum announced the discovery of five more frogs, including two females, and in light of their gloomy prospects in the wild, they were brought back to the aquarium. Romeo finally has his Juliet, and a shot at fatherhood.

Each spring, the common frogs in my urban backyard pump out prodigious amounts of spawn seemingly at the drop of a hat, so I naively supposed that the course of Romeo’s romance would now run smooth, and looked forward to news of tadpoles. But no: A little reading revealed that captive frogs aren’t always so obliging. What floats one frog’s boat leaves another unmoved—and the rarer the species, the less chance of discovering what gets it in the mood. So, what to do if rarities such as Romeo and Juliet don’t or won’t do what’s needed to save their species?

Read: The last of its kind

For some frogs and toads, reproductive technologies could be the answer. Advances in the rapidly evolving fields of amphibian hormone therapy, artificial fertilization, and cryopreservation are beginning to improve the odds of tiny captive populations producing healthy tadpoles. So far, the number of threatened species benefiting from these technologies is small, but as the Australian reproductive biologist Aimee Silla of the University of Wollongong told me, the lessons being learned are paving the way to help many more. “These technologies have a lot of potential,” says Silla, who reported on the field’s mounting achievements with her colleague Phillip Byrne in the Annual Review of Animal Biosciences. “And there are exciting breakthroughs all the time, so we have reason to be optimistic.”

Earth’s biodiversity is shrinking at unprecedented speed, and amphibians are on the front line, losing a greater proportion of species than any other vertebrate group. In 2017, the International Union for Conservation of Nature listed some 2,100 amphibians as at imminent risk of extinction—almost 32 percent of all the species known—and it estimates the figure could be as high as 55 percent.

Behind the losses are the usual suspects—disappearing habitat, changing climate, pollution, and overexploitation for food and the exotic-animal trade—but with the addition of the worst wildlife disease ever documented, chytridiomycosis. A recent assessment of this catastrophic fungal disease concludes that it has led to the decline of at least 500 amphibian species and the extinction of at least 90.

Read: The worst disease ever recorded

Herpetologists began sounding the alarm in the late 1980s, and their fears prompted the first global assessment of frogs and toads and their kin. The results, published in 2004, were shocking. Populations everywhere were plummeting; some species had vanished. The following year, international experts held a summit to hash out an action plan, and one key recommendation was that zoos, aquariums, and other organizations with suitable facilities should “rescue” the species closest to extinction and breed them in captivity.