Although large animals can move quickly thanks to their long appendages, their capacity to move in response to climate change is also affected by their need to dissipate the heat produced by their large bodies.
About 3 million years ago, an extinct arctic fox ancestor roamed the icy regions of the Tibetan Plateau as its sole habitat. But a later ice age led to a massive migration that spread these foxes to the northern latitudes where they are now. In response to the changing climate, arctic foxes and many other species may once again have to travel great distances as the Earth's temperature rises.
Alexander Dyer and colleagues from the German Research Center for Integrative Biodiversity and the Friedrich Schiller University of Jena have now studied the physical limitations on an animal's mobility. Their groundbreaking discovery is that when assessing the speeds at which animals can safely move, heat dissipation as well as body mechanics must be considered. According to the findings, larger animals are more vulnerable to climate change and limited resources, as their movements are restricted by the need to maintain their body temperature.
Numerous studies have examined the links between an organism's size and its mobility. For example, previous research discovered a general scaling equation that links an animal's top speed to body mass. Depending on the mode of transport, these assessments use a mechanical model with a typical length for the animal's locomotion-related appendages (legs, wings, or fins). By estimating the volume and density of the animal, this length is then linked to the mass of the animal. The result is an equation in which mass is increased to a power between +1/6 and +1/3 and velocity scales with that power.
This ratio suggests that large animals typically need to travel at higher speeds than smaller creatures do.
However, just because an animal has the mechanical ability to move at a certain speed does not mean that this speed can be maintained by the body over a long period of time. Dyer and colleagues concluded that the possibility of overheating is one of the reasons limiting animal movement. An animal will either stop to cool off or move more slowly if it needs to expel the heat produced by its muscles. In both cases, the animal's range of motion is limited. Heat loss scales with surface area, while heat generation scales with volume.
Among the 532 species sampled are animals that can walk, swim and fly, from ants to elephants, from minnows to whales, from hummingbirds to swans. According to the team's model, the transition rates for each mode of transportation rose to the highest value with mass and then began to decrease for the largest creatures.
The conceptual simplicity and adaptability of Dyer and colleagues' analysis pleased Dries Bonte, an ecologist at the University of Ghent in Belgium. He also points out that large species are already among the rarest because of the space they require and their slow reproductive rate. According to recent findings, slow dispersal rates increase their susceptibility to climate change.
Source: physics.aps.org/articles/v16/82
Günceleme: 18/05/2023 19:36