The parable of the boiling frog goes as follows: “If you drop a frog into boiling water, it will jump out and survive. But if you turn up the temperature slowly, it will remain there until it dies.” This, of course, is a lie. Throwing a frog splashing into boiling water will harm it to the point that jumping out is infeasible. However, new science suggests that putting them in ovens may be the saving grace of all frog-kind.

This story begins in the early 20th century with pregnancy tests. Before the modern stick, doctors had the romantic job of injecting African clawed frogs with the urine of a possibly pregnant woman. If the woman was pregnant, this would trigger ovulation in frogs, a remarkably reliable process. However, when the first at-home pregnancy tests hit the shelves in 1978, testing labs holding hordes of ovulating frogs simply released them into the surrounding environment, unknowingly causing the spread of an invasive species along with a lethal disease they carried. This disease ran inconspicuously rampant among amphibians everywhere, causing the extinction or decline of over 200 amphibian species.  

That was, until the 1990s, with the groundbreaking discovery of the tiny fungus that had caused so much trouble for amphibian communities. Amphibian chytrid fungus, and certified mouthful, Batrachochytrium dendrobatidis (Bd), had destroyed amphibian populations, causing disease with a near 100% mortality rate in many species. Bd is specifically harmful to amphibians because it encysts on the skin, which is the organ through which amphibians breathe and metabolize (also why you shouldn’t handle them with dirty hands!). As it hardens, these amphibians lose access to oxygen, creating a catastrophe for amphibian ecosystems. Despite the disease’s severity, however, scientists observed something curious: while Bd is a death sentence for many frogs, others walked away scott-free. 

A sliver of hope was found when scientists began to notice a relationship between environmental temperature and Bd’s harmfulness. They found that in areas with higher temperatures or with amphibians who could raise their internal temperature, Bd remained powerless. The spores’ weakness created some hope, but still left frogs in colder environments desperate. It would be unfeasible to take every infected individual to a warmer climate, provide chemical treatment, or vaccinate faster than Bd could spread. But a 2024 study offers a new plan to mitigate this disease. The researchers put infected frogs in three different environments: a cold, 66F environment, a warm environment dependent on the species’ preferred temperature, and an environment with a temperature gradient where frogs could move to colder or warmer spaces. As expected, the intensity of the infection was much greater for the cold-trail frogs. However, the fates of the gradient-trial frogs were what made this study interesting. They found that infected frogs, when given the choice, chose to bask in the warm air, a type of behavioral fever. While human bodies get fevers regardless of whether or not they want to, these frogs consciously seek them out to fight disease. Moreover, frogs in the temperature-gradient environment were actually less sensitive to Bd than those in the warm-environment trial. This gradient treatment even gave frogs greater immunity to Bd, leaving them unaffected on the second inoculation.

This discovery has led to a simple yet obvious solution for our amphibious friends: put them in ovens. Simple stacks of bricks, which conserve heat, are saving the day as miracle-working “frog saunas”. Placing the economically efficient devices in areas at risk of Bd provides the temperature gradient designed in the study to grant them immunity to Bd. So instead of boiling water to prevent a frog from jumping out, install a sauna for a frog to jump in.