A recent review of the existing scientific literature found evidence suggesting that warm-blooded animals may be literally shape-shifting to adapt to climate changes. According to Allen’s rule, animals living in warmer climates have larger appendages than those living in cold climates, which helps increase the available surface area for heat loss to the environment. Such heat exchange mechanisms are very important in thermoregulation to avoid retaining excess heat.
The authors of the review published in Trends in Ecology and Evolution cite a report concluding that 58% of the 110 bird species studied show increases in beak size. In fact, Australian parrots have increased their beak size by 4-10% since 1871. This is notable as a bird’s beak contains a lot of blood vessels. Thus, such increases in beak size may help birds more effectively get rid of excess body heat. Studies have also shown that birds raised in hotter temperatures direct more blood flow to their beaks that those raised in cooler temperatures. Thus animals with larger beaks may have higher survival rates in hot years as compared to animals with smaller beaks. Similar to birds, bats and shrews appear to be shape-shifting with larger ears, tails, and legs (and in the case of bats, wing size) that correspond to increasing environmental temperatures.
While these results are certainly intriguing, it is difficult to point the finger only at temperature when it comes to factors that might alter the body shape of an animal as climate change also affects water and food availability among other factors. In addition, while exposure of animals to hotter temperatures has been shown to change the animal’s shape, whether or not these changes are passed to their offspring needs more exploration. While some animals appear to be shape shifting in response to climate change, others may adapt by moving to areas with temperatures closer to their preferred range.
As summer nears the end, I feel my ears growing…
S Ryding, M Klaassen, GJ Tattersall, JL Gardner, MRE Symonds. Shape-shifting: changing animal morphologies as a response to climate warming. Trends in Ecology and Evolution. In press. DOI: https://doi.org/10.1016/j.tree.2021.07.006