When survival is a stretch: How animals are adapting to climate change

But research shows that Mother Nature tends to hit the Fast Forward button every now and then, particularly when it’s a matter of survival or extinction. As Earth gets warmer, scientists are discovering that birds, animals and insects are changing their very forms, behaviours and preferences, sometimes within a few generations, to simply cope.

Some are literally going to new lengths. Wood mice in Spain are now born with longer ears than they did 30 years ago. The elongation helps dissipate more body heat in a warming world. In Alaska, masked shrews are getting longer legs than their ancestors 50 years ago to help regulate their body heat in the same way.

Others are revamping their wardrobes to prep for changing climatic conditions. In southern Finland, tawny owls used to be mostly pale grey, blending well with the snowy landscape. But data over 28 years shows that as winters get milder, there are dramatically more dark brown owls in each flock. Animal menus are changing too. Vegetation patterns in Alaska have changed so much in the last century that local Kodiak bears now show a marked preference for berries over the usual fish.

Changes in shape, size, and structure have always occurred in animals, says Deakin University bird researcher Sara Ryding. But where most previous identifications of bodily changes were linked to modifications in food or habitat, we now find clear links to the climate crisis. “The climate is changing at an unnaturally fast pace, which places unique pressure on animals,” Ryding says.

“We do not know whether they will be able to respond in the future, and whether they will be able to survive.”

These aren’t responses to a new predator, The threat is the planet itself, or rather, what humans are doing to it. See how some of Earth’s inhabitants are responding.

A 2021 study, published in the journal Trends in Ecology & Evolution, finds that 30 species of animals have exhibited bodily changes in response to climate change over different time periods. “We’ve found that animals are increasing the size of their appendages, relative to their body size. This is occurring in both mammals and birds, and in all parts of the world,” says Sara Ryding of Deakin University, Australia and author of the study.

Some changes are subtle, barely detectable to the untrained eye. Australian parrot beaks, for instance, have grown in size by 4-10% when compared to specimens from 1871. The wings of modern roundleaf bats, when compared to museum specimens of the species collected over 65 years, show an increase of more than 1%.

Other species show distinct differences from their close ancestors. The dark-eyed junco, a songbird common across North America, has a slightly larger bill than it used to. The adaptation coincides with short-term temperature extremes in the cold region. Ryding’s team also analysed data on the bill lengths of hundreds of Galapagos finches from 2003 to 2011. Finches with smaller bills were unable to live through hot years, resulting in more large-billed finches surviving.

For warm-blooded beings, these are essential adaptations as the decades get warmer. “Having larger appendages could mean that animals can regulate their body temperature more efficiently, because they can dissipate excess body heat when they get warm,” says Ryding. “However, we don’t know if this is helping animals survive or not.”

This is especially worrying, given that the planet is getting hotter still. “It is unusual to see changes happening within 100 years, which is a testament to how serious climate change is for animals.” Perhaps, even these responses might not be fast enough.

Anoles, a type of lizard that inhabits the Caribbean islands and South America, have undergone a particularly fascinating transformation. Local winds and storms are now so strong that they’ve evolved large toepads and stronger front legs to grip local vegetation when things get rough.

In 2018, Colin Donihue, an evolutionary ecologist and then a postdoctoral research fellow in biology at Washington University, led a study examining the anoles on the 40-odd Turks and Caicos Islands. He found that the ones that survived hurricanes Maria and Irma in 2017 had longer forelegs and larger toepads than anoles measured just six weeks before the two storms hit.

A laboratory test, using a wind tunnel and fan, demonstrated that the survivor anoles were better able to hang on to branches. It was a path-breaking study, the first one showing how a hurricane had driven natural selection and survival.

“Evolution is constant, but any group can experience periods of relative stasis and relative speediness,” says conservation biologist Thor Hanson. His book, Hurricane Lizards and Plastic Squid, maps the ways in which plant and animal species are adapting to the climate crisis. “Rapid environmental change is apt to trigger rapid evolution, because it creates severe life-and-death situations where natural selection and other evolutionary forces play out quickly,” he says. “It is concerning that climate change makes such rapid evolution necessary, but it’s not concerning to see it happen. In fact, it’s a relief,” he says. “There are many species that simply won’t be able to keep pace. Those are the ones to be worried about.”

The Plastic Squid portion of Hanson’s book’s title refers to a different kind of transformation. He looks at the Humboldt squid in Mexico’s Gulf of California that virtually disappeared from traditional fishing grounds after the waters warmed substantially in 2009 and 2010. The squid were not only still around, but more abundant than ever. Instead of migrating to cooler waters, they had changed their entire way of life.

They now mature in half the time, eat different foods, cover lifespans that are only half as long and grow to only a fraction of their former size. Adult squid used to be nearly two metres long over a decade ago, and the equipment the fishers use for jigging squid has become comically oversized for the task.

Habits are changing even as bodies adapt. On Alaska’s Kodiak island, brown bears are switching to a vegetarian diet of elderberries instead of the usual salmon because warmer temperatures are ripening the fruit earlier in the year.

In the past, salmon would spawn like clockwork at the end of July. Bears would wade into shallow rivers and subsist largely on the fish until late August, when elderberries would ripen.

The berries now ripen as early as late July, providing literal low-hanging fruit for the bears. Plucking is easier than hunting. So bears gorge on the berries alone.

It’s more than a sweet deal. Elderberries are only 13-14% protein against the salmon’s roughly 85%. So bears end up losing less energy in digestion and grow fatter more quickly, in preparation for colder seasons.

The findings are from a 2017 study conducted by biologists at Oregon State University, University of Montana’s Flathead Lake Biological Station, and Kodiak National Wildlife Refuge, and was published in the journal Proceedings of the National Academy of Sciences.

How might this dietary switch affect bears, salmon, and other creatures that relied on the age-old ecosystem? Scientists believe it could alter the vegetation and biodiversity along Kodiak’s streams in fifty or a hundred years.

Across the western Pacific, climate change is acting as a referee between angry butterflyfish. These creatures are bright and colourful, with patterns on their bodies similar to butterflies, and are normally aggressive and territorial. But the increased occurrence of reef bleaching caused by rising sea temperatures is causing them to abandon their aggression.

This is part of the findings of a 2018 study led by marine biologist Sally Keith of Lancaster University, whose team examined 17 reefs across the central Indo-Pacific in Japan, the Philippines, Indonesia and Christmas Island in the Indian Ocean.

Keith and her colleagues were initially looking into how the behaviour of butterflyfish might vary geographically — but then a mass coral bleaching event hit in 2016, and the study’s direction changed. After the coral bleaching event, hostile interactions dropped by two-thirds on average, transforming aggressors into relative pacifists in a matter of weeks.

Researchers believe that in a calorie-starved environment, butterfly fish have become docile in order to conserve energy, a behavioural shift that may help them eke out a living until they move to cooler waters.

{HOUSE GROUSE} LIFE HACKS FOR PIKASFluffing up, stretching out

The American pika, a small, nearly tailless, gerbil-shaped mammal that typically lives in the cool, moist mountains of western North America, is coping with change in its own way. Most areas of the species’s geographic range have been turning drier and hotter, shrinking distributions and population sizes. A research team led by Erik Beever of the US Geological Survey’s Northern Rocky Mountain Science Center in Montana reported in 2017 that the mammal is using flexible behaviours to survive. This includes changes in foraging habits and the use of different habitats.

American pikas typically live in alpine rock piles, where they store caches of grass to help them survive the winter. But Beever and his colleagues occasionally saw food caches of the pika on the shores of lakes and reservoirs, in downed logs, snags, slash piles, and coniferous forests. Interestingly, however, these flexible behaviors have only been observed in the cooler, more moist portions of the species’ range, but not in drier places like central Nevada or northern New Mexico.

Some pika individuals in the Columbia River Gorge meet up to 63% of their dietary needs by eating moss year-round, so they’re less engaged with shoring up grass for the winter.

They’ve found new ways to regulate their body heat too. Winter temperatures in the more northern regions are extreme. So pikas now squeeze themselves into a fluffy ball, reducing their surface area to keep warm in the winter, and stretching out to cool down in the summer.