By Dr. Becker
Koalas, which live in eastern Australia, are known for their cuddly bear-like appearance, fuzzy fur and inquisitive eyes. They’re often referred to as koala “bears,” but this is technically incorrect.
Koalas are marsupials, not bears, which means they’re a “pouched mammal” that gives birth to live, underdeveloped young that must continue to grow inside the marsupials’ pouch, or marsupium.
When a marsupial gives birth, the offspring (still in the embryo stage) climbs from the birth canal into the pouch and attaches to the mother’s nipple. It stays there attached to the nipple for the rest of its developmental period, which in most other mammals occurs while still in the womb.
They give birth early because they do not develop a placenta, which allows for a longer gestation period in utero. There are about 200 species of marsupials in all, but the koala is arguably one of the most widely adored.
Koalas Spend Most of Their Lives in Eucalyptus Trees
There’s a reason why the quintessential image of a koala often pictures it clinging to a tree. Aside from their first year of life, which is spent clinging to its mother’s back or belly, koalas spend most of their time in eucalyptus trees, lounging, eating and sleeping (for 18 to 20 hours a day).1
They sleep so much because they eat a low-nutrition diet that requires a lot of energy to digest. Sleeping is the best way to conserve energy while this intensive process takes place. While koalas are technically nocturnal, they sometimes are awake during daylight hours as well.
Koalas eat about 2.5 pounds of their favorite food, eucalyptus leaves, per day — so many that they even begin to smell like them! According to National Geographic:2
“A special digestive system — a long gut — allows koalas to break down the tough eucalyptus leaves and remain unharmed by their poison. Koalas eat so many of these leaves that they take on a distinctive odor from their oil, reminiscent of cough drops.”
With such dependence on eucalyptus trees, koalas are being seriously threatened by habitat loss, including from intentional clearing for urban development, bushfires and diseases like dieback, which target the trees.
Each koala bear needs about 100 trees, which is becoming increasingly difficult as eucalyptus trees in Australia’s forests and woodlands disappear.3 In addition, while there are more than 600 varieties of eucalyptus, koalas are very picky eaters and will only eat some of these.
How Baby Koalas Adapt to Eat Toxic Eucalyptus Leaves
Eucalyptus leaves are toxic to most mammals, so how do koalas thrive on them? A baby koala, or joey, feeds on its mother’s milk alone for about six months, but after that it consumes “pap,” which is a runny form of droppings from its mother.
This passes along special microorganisms from its mother’s intestines to the joey, which allow the baby koala to safely digest eucalyptus leaves. Joeys eat pap for several weeks before emerging from the pouch to ride on its mother’s back or abdomen.4
While young koalas will continue to drink their mother’s milk for as long as they can fit inside her pouch, adult koalas typically get all the moisture they need from eucalyptus leaves (although they may take a drink of water in times of drought).
The Unique Way Koalas Keep Cool
Tree trunks can be more than 40 degrees F cooler than the air around them. When researchers observed 30 koalas during a spell of hot weather in Australia, they were found often hugging trees. This is not only characteristic of the animals, it also serves an important purpose of helping them cool off.
During extreme heat waves, up to one-quarter of certain koala populations have died. Having access to trees could make a major difference in the animals’ ability to survive during extreme heat, not only by reducing their heat stress but also by reducing their water needs.5
In fact, when the researchers took heat imagery of the koalas, they were able to see their body temperatures respond to the cooling trees. The animals even have thinner fur on their bellies, which the researchers believe helps them maintain close contact with the tree trunk’s cooling effects.
Koalas Are Listed as a ‘Vulnerable’ Species, but That May Not Be Enough
In 2012, koalas were added to Australia’s list of vulnerable species, but since that time the Australian Koala Foundation (AKF) notes nothing has changed and “koala populations are still rapidly declining.”6
AKF estimates that there are fewer than 80,000, and perhaps as few as 43,000, koalas remaining in Australia. While the animals are protected under Australian law, about 80 percent of their remaining habitat is on privately owned land, most of which is not protected by legislation.
Unfortunately, 80 percent of koala’s natural habitat has already disappeared, and the animals are also threatened by dogs and cars, which kill 4,000 koalas every year.7
AKF is hoping to secure a Koala Protection Act to help ensure the long-term survival of koalas in Australia, modeled after the Bald Eagle Protection Act of the U.S., which prohibits selling, killing or possessing the species.
Like bald eagles, koalas were once widely hunted (during the 1920s and ‘30s in Australia), leading to devastating population declines. Though they’ve since been reintroduced to much of their former range, National Geographic reports that “their populations are smaller and scattered.”8
“With such strong restrictions in place, the status of the Bald Eagle slowly began to improve and it has now been removed from the threatened and endangered list all together,” AKF notes, hoping that koalas could follow the same restorative path.9
If you live in Australia and would like to get involved, you can email federal members asking for a Koala Protection Act to be put in place.