Scientists have discovered that increasing temperatures can affect the dietary choices of frogs. Researchers at the Universities of Lisbon and Uppsala studied the behavior of three kinds of amphibians to discover what effect heat waves can have on their diets.

Before publishing their findings in the journal Ecology, Germán Orizaola, co-author of the study and a researcher at the Swedish university, had been tracking the frequency and intensity of extreme weather events, such as flooding, heat waves and droughts. Orizaola stated, "Among the many challenges climate change poses to natural ecosystems, the effect it can have on the dietary preferences of living organisms is a field of study that has been attracting researchers' attention in recent years."

Biodiversity is greatly threatened by climate change, with amphibians being severely affected since they have to change their behaviour, physiology and life strategies in order to survive. Orizaola and his team studied three kinds of amphibians that inhabit the Iberian Peninsula: the European tree frog (Hyla arborea), the Mediterranean tree frog (Hyla meridionalis) and the Iberian painted frog (Discoglosus galganoi).

Since amphibians have permeable skin and a multi-stage life cycle, they are highly sensitive to climate change and global warming. "In fact, they are already experiencing sharp declines in population and extinction on a global scale, and they have become the focus of several research and conservation programs in recent decades," Orizaola explained.

Using the larvae of the three species, Orizaola and his team exposed them to various kinds of heat waves that varied in duration and intensity. "The larvae were kept in three different sets of conditions: with a solely vegetable-based diet, solely animal-based or a mixed diet. This third situation allowed us to assess whether they modified their diets towards a greater or lower percentage of vegetable matter," Orizaola recounted.

"Our results indicated first that larvae of various species have a diet adapted to the conditions under which they reproduce. The painted frog, which reproduces when it is cold, has a carnivorous diet, while the Mediterranean tree frog, which reproduces during the hottest season of the year, maintains a vegetarian diet," Orizaola noted.

The researchers discovered that the larvae of all three species have very flexible dietary habits since the amount of vegetables they consumed increased during heat wave exposure. Based on their rates of survival, growth and development, the larvae favored a vegetarian in a hotter environment.

"This phenomenon could be common to many species living in continental, aquatic environments. If so, the increased frequency and intensity of heat waves forecast by climate change models could bring about considerable changes to these environments," Orizaola concluded.