Why is it surprising that toads prefer milder winters?

The MTA ATK NÖVI Lendület (Momentum) Evolutionary Ecology Research Group was the first in the world to prove in a laboratory environment that shorter and milder winters resulting from climate change may have a positive effect on the survival and general condition of temperate-zone amphibians. Their findings were published in the open access journal, Scientific Reports.

2016. június 8.

Amphibians are the most threatened group of vertebrates and an evident population decline has been registered in nearly half of their species. Climate change is among the leading risk factors, however, no controlled experiments have been carried out to reveal the expected impacts of gradually shorter and milder winters in our region regarding the survival and general condition of amphibians. Therefore, the researchers of MTA ATK NÖVI Lendület (Momentum) Evolutionary Ecology Research Group have conducted a controlled experiment, in which juvenile common toads (Bufo bufo) have been hibernated under laboratory conditions.

The common toad source: Miklós Laczi

In the experiment, the effects of milder and shorter winters expected to result from climate change were simulated by keeping toads at two different temperatures (1.5 and 4.5 °C) for a period of 91 or 61 days. According to the results, conditions simulating a mild and short winter increased the chance of survival for the animals and caused smaller loss of body mass compared to settings resembling current winter conditions.

Tolerating warm weather in cold blood

All this is really fascinating if we stop to consider the fact that toads hibernate in the winter and do not eat anything during this period. Previously, it had been assumed that higher environmental temperatures could lead to increased metabolic rates in animals with inconsistent body temperatures (commonly known as cold-blooded animals). Therefore, hibernating toads would have been expected to have less of a chance of survival at elevated temperatures because of depleting their energy reserves faster. However, under laboratory conditions, the exact opposite has been proven by the Hungarian researchers.

While an increased survival rate during hibernation is clearly a positive effect, better health conditions may also have beneficial effects on post-hibernation survival and efficient reproduction. However, researchers contributing to the experiment also claim that this endangered group of animals still have to face serious challenges relating to climate change such as more frequent periods of drought and the spread of invasive predators and infectious diseases which are responsible for decreasing the number of amphibians worldwide.

Please click here to read the entire research article.