Shape-shifting: changing animal morphologies as a response to climatic warming

Many animal appendages, such as avian beaks and mammalian ears, can be used to dissipate excess body heat. Allen's rule, wherein animals in warmer climates have larger appendages to facilitate more efficient heat exchange, reflects this. We find that there is widespread evidence of 'shape-shifting' (changes in appendage size) in endotherms in response to climate change and its associated climatic warming. We re-examine studies of morphological change over time within a thermoregulatory context, finding evidence that temperature can be a strong predictor of morphological change independently of, or combined with, other environmental changes. Last, we discuss how Allen's rule, the degree of temperature change, and other ecological factors facilitate morphological change and make predictions about what animals will show shape-shifting.

Automated summary

Animal appendages like avian beaks and mammalian ears can dissipate excess body heat, with animals in warmer climates typically having larger appendages for more efficient heat exchange. In response to climate change and warming, endotherms may undergo 'shape-shifting' in appendage size. Temperature is found to be a strong predictor of morphological change in endotherms, either independently or in combination with other environmental factors.