Global warming causes not only a general increase in temperatures, but also an increase in the frequency and intensity of extreme weather events, such as floods, heat waves and droughts. These environmental changes pose a challenge for many organisms, including amphibians, which must modify their behavior, physiology and life strategies to survive.
Researchers at the Universities of Lisbon (Portugal) and Uppsala (Sweden) have studied the behavior of three types of amphibians that inhabit the Iberian Peninsula, such as the San Antonio frog (Hyla arborea), the southern frog (Hyla meridionalis) and the Iberian pintojo frog (Discoglosus galganoi) to find out how heat waves can influence your diet.
"Among the many challenges that climate change poses in natural ecosystems, the effect they can have on the food preferences of living organisms is a field of study that has been attracting the attention of researchers in recent years", declares Sinc Germán Orizaola, co-author of the work published this week in the journal Ecology and a researcher at the Swedish university.
Amphibians are a group highly sensitive to global warming due to the permeability of their skin and their complex life cycle, which combines an aquatic phase as larvae and a terrestrial phase as juvenile and adult. "In fact, they are already experiencing sharp population declines and extinctions on a global scale, and have become the focus of numerous research and conservation programs in recent decades," emphasizes the scientist.
Vegetable, animal or mixed diet
The researchers did a laboratory experiment in which they exposed the larvae of these three species to different types of heat waves that varied in duration and intensity - increasing the temperature of the water where they developed.
“The larvae were kept in three different situations: with only plant food, only animal or mixed diet. This last situation is what allowed us to evaluate whether they modified their diet towards a higher or lower percentage of plant matter ”, adds Orizaola.
Likewise, they examined the relationship between different isotopes of carbon and nitrogen in the tissues of larvae with mixed feeding, and compared them with those of 'menus' exclusively vegetable or animal. This allowed them to reconstruct the type of diet selected by the larvae exposed to a combined regimen.
“Our results indicated, first, that the larvae of the different species have a diet adapted to the conditions in which they reproduce. The pintojo toad, which does so in cold periods, maintains a carnivorous diet, while the southern frog, which reproduces during the hottest season of the year, follows a vegetarian diet ”, says the researcher.
The most relevant result is that these larvae have very flexible feeding habits. The three species increased the percentage of vegetables in the face of heat waves. When analyzing the survival, growth and development rates of the larvae, a reduction in the efficiency of the carnivorous diet was found in favor of the vegetarian one under hot conditions.
“This could be a phenomenon common to many species that inhabit continental aquatic environments. If so, the increase in the frequency and intensity of heat waves predicted by climate change models could generate notable changes in these environments ”, concludes Orizaola.
B. M. Carreira, P. Segurado, G. Orizaola, N. Gonçalves, V. Pinto, A. Laurila and R. Rebelo 2016. “Warm vegetarians? Heat waves and diet shifts in tadpoles ”. Ecology97. doi: 10.1002 / ecy.1541 http://onlinelibrary.wiley.com/wol1/doi/10.1002/ecy.1541/abstract