After drier summers, survival of small-beaked birds was reduced.īut we found clear evidence that birds with smaller beaks are also less likely to survive hotter summers. These data do demonstrate rainfall (and, by extension, seed size) determines beak size. Our research examined previously collected data to determine if temperature also influenced changes in beak size of these finches. This means scientists have sometimes focused on other reasons that might explain changes in animal body shape.įor example, studies have shown the average beak size of the Galapagos medium ground finch has changed over time in response to seed size, which is in turn influenced by rainfall. Of course, animal appendages have uses far beyond regulating body temperature. Thermal image of a king parrot, showing that the beak is warmer than the rest of the body. In fact, as far back as the 1870s, American zoologist Joel Allen noted in colder climates, warm-blooded animals-also known as endotherms-tended to have smaller appendages while those in warmer climates tend to have larger ones. This heat-dispersing function is depicted in the thermal image of a king parrot below, which shows the beak is warmer than the rest of the body.Īll this means there are advantages to bigger appendages in warmer environments. The beaks of birds perform a similar function-blood flow can be diverted to the bill when the bird is hot. African elephants, for example, pump warm blood to their large ears, which they then flap to disperse heat. It's well known that animals use their appendages to regulate their internal temperature. The pattern is widespread, and suggests climate warming may result in fundamental changes to animal form. In doing so, we identified multiple examples of animals that are most likely 'shape-shifters'-including species in Australia. We reviewed the published literature and found examples of animals increasing appendage size in parallel with climate change and associated temperature increases. Our new research examined another way animal species cope with climate change: by changing the size of their ears, tails, beaks and other appendages. And others evolve to change their body size to cool down more quickly. Some change the timing of key life events such as breeding and migration, so they take place at cooler times. Some move to cooler areas, such as closer to the poles or to higher ground. Animals are dealing with global warming in various ways.

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