Global warming is triggering an “alarming” evolutionary reaction in warm-blooded animals with some experiencing shifts in their body shapes as a coping mechanism to rising temperatures, according to a new review of existing research.
Animals are getting larger beaks, legs and ears that allow them to better regulate their body temperatures as the planet gets hotter, with birds particularly affected, said Sara Ryding, a researcher at Deakin University in Australia and one of the authors of the research that published on Tuesday in the journal Trends in Ecology & Evolution.
Scientists gave the example of Australian parrots, such as gang-gang cockatoos and red-rumped parrots, who have shown a than 10 percent increase in their bill size in the last 150 years.
“It means animals are evolving, but it does not necessarily mean that they are coping with climate change. We can see that some species have increased in appendage size so far, but we don’t know if they will be able to keep up as the climate crisis worsens,” Ryding said
“We also don’t know whether these shape-shifts actually aid in survival (and therefore are beneficial) or not. 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.”
Several other species of birds have shown an increase in bill size, while other animals are also reporting physical changes. Wood mice have bigger ears while some bats are now boasting an upgraded, larger set of wings.
Ryding said that the changes were subtle and unlikely to be immediately noticeable but could be “functionally important.”
While climate warming was a “compelling argument” as the driving force behind these changes in shape, the study said that it was difficult to “establish causality with confidence” given the multifaceted effects climate change has on the environment.
Smaller bodies, bigger appendages
Within an animal species, individuals in warmer climates have larger appendages, such as wings and beaks -- a pattern known as Allen’s rule, with the greater surface area allowing the animals to control their temperature more easily, the study noted.
At the same time, body sizes tend to shrink, since smaller bodies hold onto less heat.
In the US, a recent study of 70,716 migratory birds representing 52 species showed that they have been getting smaller over the past four decades, and their wingspan wider. The birds all died when hitting high-rise buildings in Chicago during migration and were collected by the city’s Field Museum.
“Both of our studies look at how animals respond to climate change by altering their surface area to volume ratio,” explained Ryding.
It said that more research on different species and in different ecosystems was needed to determine how wide the phenomenon was and could help predict which species might shape-shift in the future.