Australia is home to a wide range of unique animals. These evolved on the continent when it separated from Antarctica and drifted northwards, around 45 million years ago. Creatures such as kangaroos and koalas are found only in Australia, as you’ll know if you’ve ever read a koala story book. But how did they come to be so well-suited to life on a hot, dry continent? Let’s take a look. 

Early koalas

Around 30-40 million years ago, koalas and wombats - koalas’ closest living relatives - diverged. Wombats stayed on the ground while koalas headed up into the trees where there was less competition for food. Millions of years ago Australia was blanketed in lush forests, and fossils show that they supported several species of koala, some of which were giant in size. 

One species of giant koala, called Nimbadon, is thought to have evolved around 15 million years ago and eaten fruit and other vegetation. Hiding in the trees was necessary for survival, as it shared its world with flesh-eating kangaroos, marsupial lions and crocodiles. It’s thought that there was a large population of Nimbadon until around 12,000 - 15,000 years ago, when the creature was in decline. It likely went extinct around 11,000 years ago when other Australian megafauna (very large animals) were disappearing.

Smaller is better

So why did today’s smaller koalas survive when the Nimbadon didn’t? Well, in evolutionary terms bigger is not always better. Larger animals need a lot of food, and due to a changing climate, Australia was getting hotter and drier. The forests were gradually replaced by deserts, meaning food was scarce and larger animals couldn’t find enough to eat. 

In addition, there was a shift towards eucalyptus woodlands, which were able to thrive in the warmer climate. The smaller koalas that had adopted these trees as their home and food source weren’t threatened by changes to their habitat, and continued to flourish. 

Adaptations to life in the trees

When koalas first moved into the trees they quickly developed a range of features that made arboreal life easier. Their limbs became powerful and their paws adapted to have opposable thumbs and long claws, which allowed them to grip tree trunks. They also developed a tough pad on their bottoms so they could stay comfortable while sitting in the trees for long periods. Their woolly coats help them to control their body temperature, while their specialised digestive systems enable them to eat eucalyptus leaves, which are fibrous and toxic to other animals. 

As they evolved, koalas also gained an exceptional sense of smell, which today helps them to detect toxin levels in different eucalyptus leaves and select those with the least toxins and the most nutritional value. 

Discover The Koala Who Could

If you’re interested in seeing a koala story on stage, don’t miss the new show, The Koala Who Could. Adapted from Rachel Bright and Jim Field’s bestselling picture book, it tells the story of Kevin the koala with stunning puppetry and sing-along songs. Perfect for kids aged three and up, it’s currently touring the UK. Book tickets today at your local venue.