Ecothermic animals depend on external sources for their body heat because they lack the ability to retain the heat generated by their own metabolism. So when it's cold outside, the temperature of these so-called "cold-blooded" creatures drops and their metabolism slows down. When it's hot, the opposite happens.
It could then be assumed that warmer temperatures caused by climate change will benefit many ectothermic animals, including lizards, snakes, and amphibians. They will become more active and less at the mercy of changes in outside temperature.
However, others have postulated that a faster metabolism triggered by warmer weather will cause accelerated aging in these animals, leading to a shorter lifespan in them.
According to a centuries-old dominant theory called "life rate," the faster an organism's metabolic rate, the shorter its lifespan. This is why fast-living creatures like mice have a lifespan of only a few years, while some slow-living tortoises can last more than a century.
A team of researchers from Tel Aviv University in Israel and Queen de Belfast University in Northern Ireland decided to see what will happen to cold-blooded animals if their metabolism is accelerated by warming temperatures. To do so, they analyzed data from more than 4,100 terrestrial devertebrate species.
What they have found, as they document in a new study, is that a warm environment accelerates the rate of life in cold-blooded animals, causing them to age faster and die younger.
"The link between the lifespan of cold-blooded animals (amphibians and reptiles) and ambient temperature could mean that they are especially vulnerable to the unprecedented global warming the planet is currently experiencing," said Gavin Stark, a doctoral student at Tel University. Aviv who was the lead author of the study. "In fact, if rising ambient temperatures reduce longevity, it can make these species more likely to become extinct as the climate warms."
What this could mean is that cold-blooded animals could be especially at risk of going extinct in a warmer world. "Now that we know that the life expectancy of cold-blooded vertebrates is linked to environmental temperatures, we could expect to see their lifespan further shortened as temperatures continue to rise through global warming," said Daniel Pincheira-Donoso, professor. Deevolution and Macroecology at the Faculty of Biological Sciences at Queen'sUniversity Belfast.
Ectothermic animals are already a highly threatened group, according to conservationists, with about 20% of the roughly 10,000 species of lizards, snakes, turtles, crocodiles, and other reptiles facing the possibility of extinction. Ongoing climate change will hit many of these species further.
"We need to further develop our understanding of this link between biodiversity and climate change," says Pincheira-Donoso. "Only armed with knowledge can we inform future policies that could prevent further damage to the ecosystem."