Some warm-blooded animals are experiencing shifts in their body shapes, likely as a response to the pressures of climate change, 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.
The biggest shifts in appendage size in the more than 30 animals they looked at in the review were among some Australian parrot species, which saw their beak size increase by 4% to 10% on average since 1871.
"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 via email.
"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."
She 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 United States, 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.
While most research on morphological change over time has focused on birds, the paper noted that shrews and bats have increased their relative ear, tail, leg and wing sizes.
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.
"Previous studies have shown cases where shape-shifting is happening, but these have focused on individual species or groups. Our review paper combines all of these to show how widespread this phenomenon seems to be," Ryding said.
The warming climate is causing animals to "shapeshift"
VIDEO: THIS VIDEO ABSTRACT DESCRIBES THE MAIN POINTS OF THE TRENDS IN ECOLOGY & EVOLUTION REVIEW "SHAPE SHIFTING: CHANGING ANIMAL MORPHOLOGIES AS A RESPONSE TO CLIMATIC WARMING." view more
CREDIT: RYDING ET AL.
Climate change is not only a human problem; animals have to adapt to it as well. Some “warm-blooded” animals are shapeshifting and getting larger beaks, legs, and ears to better regulate their body temperatures as the planet gets hotter. Bird researcher Sara Ryding of Deakin University in Australia describes these changes in a review published September 7th in the journal Trends in Ecology and Evolution.
“A lot of the time when climate change is discussed in mainstream media, people are asking ‘can humans overcome this?', or ‘what technology can solve this?'. It’s high time we recognized that animals also have to adapt to these changes, but this is occurring over a far shorter timescale than would have occurred through most of evolutionary time,” says Ryding (@zuuletc). “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 notes that climate change is a complex and multifaceted phenomenon that’s been occurring progressively, so it is difficult to pinpoint just one cause of the shapeshifting. But these changes have been occurring across wide geographical regions and among a diverse array of species, so there is little in common apart from climate change.
Strong shapeshifting has particularly been reported in birds. Several species of Australian parrot have shown, on average, a 4%–10% increase in bill size since 1871, and this is positively correlated with the summer temperature each year. North American dark-eyed juncos, a type of small songbird, had a link between increased bill size and short-term temperature extremes in cold environments. There have also been reported changes in mammalian species. Researchers have reported tail length increases in wood mice and tail and leg size increases in masked shrews.
“The increases in appendage size we see so far are quite small—less than 10%—so the changes are unlikely to be immediately noticeable,” says Ryding. “However, prominent appendages such as ears are predicted to increase—so we might end up with a live-action Dumbo in the not-so-distant future.”
Next, Ryding intends to investigate shapeshifting in Australian birds firsthand by 3D scanning museum bird specimens from the past 100 years. It will give her team a better understanding of which birds are changing appendage size due to climate change and why.
“Shapeshifting does not mean that animals are coping with climate change and that all is ‘fine,’ says Ryding. “It just means they are evolving to survive it—but we’re not sure what the other ecological consequences of these changes are, or indeed that all species are capable of changing and surviving.”
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The authors received financial support from the Australian Research Council Discovery Project, an Australian Research Council Future Fellowship, and a Natural Sciences and Engineering Research Council of Canada Discovery Grant.
Trends in Ecology & Evolution, Ryding et al.: “Shape-shifting: changing animal morphologies as a response to climatic warming” https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(21)00197-X
Trends in Ecology & Evolution (@Trends_Ecol_Evo), published by Cell Press, is a monthly review journal that contains polished, concise, and readable Reviews and Opinions in all areas of ecology and evolutionary science. It aims to keep scientists informed of new developments and ideas across the full range of ecology and evolutionary biology—from the pure to the applied, and from molecular to global. Visit: http://www.cell.com/trends/ecology-evolution. To receive Cell Press media alerts, please contact press@cell.com.
JOURNAL
Trends in Ecology & Evolution
METHOD OF RESEARCH
Literature review
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
Shape-shifting: changing animal morphologies as a response to climatic warming
ARTICLE PUBLICATION DATE
7-Sep-2021
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