All living things need energy to survive. They use it for breathing, circulation, digestion and movement. Young animals use the energy to grow and reproduce later in life.
A higher body temperature increases the rate at which the animal uses energy. Because cold-blooded animals regulate their body temperature based on the thermal conditions of their environment, they require more energy as the planet warms.
However, our new study, published today in the journal Nature Climate Change, shows that temperature is the only environmental factor that does not affect the future energy needs of cold-blooded animals. How they interact with other species will also play a role.
Our results show that cold-blooded animals will require more energy in a warmer world than previously thought. This may increase the risk of their disappearance.
what we already know
The amount of energy that animals use at any given time is called their metabolic rate.
Many factors affect metabolic rate, including body size and activity level. Large animals have a higher metabolic rate than small animals, and active animals have a higher metabolic rate than inactive animals.
The metabolic rate also depends on body temperature. This is due to the fact that temperature affects the rate of biochemical reactions involved in energy metabolism. In general, if an animal's body temperature rises, its metabolic rate increases exponentially.
Most animals living today are cold-blooded or "ectotherms". Ectotherms are almost all animals, with the exception of insects, worms, fish, crustaceans, amphibians and reptiles - mammals and birds.
Human-induced climate change is predicted to increase the body temperature of cold-blooded animals as global temperatures rise.
The researchers report that the metabolic rate of some terrestrial exotherms has already increased from 3.5% to 12% due to global warming. However, this prediction does not take into account the ability of animals to "adapt" physiologically to warmer temperatures.
Adaptation refers to the ability of an animal to adjust its physiology to changes in its environment.
However, adaptation can rarely completely reverse the effect of temperature on metabolic processes. For this reason, the metabolic rate of Earth's exotherms is predicted to be about 20–30% higher by the end of the century than it is now.
A higher metabolic rate means that animals need more food. This means they can starve when food is scarce, leaving them with less energy to find mates and reproduce.
Our research
Previous research efforts to understand climate warming energy costs for ectotherms have been limited to one main area. Basically, they used animals to study in relatively simple laboratory conditions, where their only problem was temperature change.
However, animals in the wild have more problems. It includes interactions with other species such as competition for food and predator-prey relationships.
Although species interact all the time in nature, we rarely study how this affects metabolic rate.
We wanted to know how interactions between species could change predictions of drastic global warming damage to cold-blooded animals. To do this, we turned to the fruit fly (genus Drosophila).
Fruit flies lay their eggs in decaying plant material. The larvae that hatch from these eggs interact and compete for food.
Our research involved rearing fruit flies individually or together at different temperatures. We found that when two fruit fly species competed for food at higher temperatures, they were more active as adults than when they were not competing with other species such as larvae. This means that they used more energy.
From this, we can use simulations to estimate that species interactions at higher global temperatures increase fruit fly future energy requirements by 3-16%.
These results indicate that previous studies have underestimated the energy cost of climate warming for ectotherms. This means that purely physiological methods may not be enough to understand the effects of climate change on cold-blooded animals.
let's get real
Understanding the energy needs of animals is essential to understanding how they survive, reproduce and thrive in harsh environments.
In a warmer world, warmer exotherms will need more energy to survive and reproduce. If they don't get enough food to meet their body's energy needs, they may be at an increased risk of death.
Clearly, we need to be better at predicting how global warming will threaten biodiversity. This means studying how animals react to changes in temperature under more realistic conditions.
This article is republished from The Conversation under a Creative Commons license. Read the original article. 
Citation : Scientists discover new way climate change threatens cold-blooded animals (March 5, 2023) by HTML
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