A comprehensive review of existing research has found that some warm-blooded animals are undergoing changes in their body shapes as a response to the pressures of climate change.
As the planet warms, animals' beaks, legs, and ears grow larger, allowing them to better regulate their body temperatures, with birds being the most affected, according to Sara Ryding, a researcher at Deakin University in Australia and one of the authors of the study published in the journal Trends in Ecology & Evolution on Tuesday.
Shapeshifting is likely to continue as the temperature warms, according to the paper. The thermoregulatory demands placed on animals are expected to be influenced by higher temperatures associated with climate change, the study argued.
"We don't know whether these shape-shifts actually aid in survival (and therefore are beneficial) or not," Ryding said. "This phenomenon of shape-shifting shouldn't be seen as a positive, but rather it is alarming that climate change is pushing animals to evolve like this, under such a relatively short timeframe."
The changes, she noted, were minor and unlikely to be noticed right away, but they could be "functionally important."
Some Australian parrot species saw their beak size expand by 4% to 10% on average since 1871, the largest change in appendage size among the more than 30 animals examined in the review.
When animals become overheated, birds use their beaks to distribute the heat, while mammals use their ears. In warmer climates, certain animals have evolved larger beaks or ears to help them expel heat more quickly. As the climate warms, these differences will become more obvious.
Animals can overheat and die if they are unable to regulate their body temperature. Beaks, which are not covered by feathers and hence are not insulated, as well as ears, tails, and legs in mammals that are not covered by fur, are sites of substantial heat exchange.
While most studies on morphological change in birds have focused on birds, the study noted that shrews and bats had grown their relative ear, tail, leg, and wing sizes through time.
More research on diverse species and ecosystems was needed, according to the study, to assess how widespread the phenomenon was and to determine which species would shape-shift in the future.
"The climate change that we have created is heaping a whole lot of pressure on them, and while some species will adapt, others will not," Ryding said.
