- I think that only daring speculation can lead us further and not accumulation of facts. Albert Einstein
Hold a Koala
Koalas do not belong to the category of bears. English-speaking people of the 18th century referred to them that way because of their resemblance with bears. Though the term koala bears is still in use, it is incorrect to refer to koalas as bears.
Koalas, the extremely cute-looking and cuddly species of marsupials, are found in abundance in Australian states like Queensland, Victoria, New South Wales and some places in eastern and southern Australia. The fact that koalas have established their habitat in the eucalyptus forests and coastal islands of eastern and southern Australia doesn't come as a surprise as their diet mainly consists of eucalyptus leaves which are found in abundance in this region. Eucalyptus trees don't just fulfill their food requirements, but also protect them against their predators; that explains why they spend most of their time on these trees.
Koalas are known to feed on the leaves of different species of eucalyptus trees found in their native habitat. These leaves don't just provide them all the necessary nutrients, but also fulfill their water requirements, as 50 percent of the content of eucalyptus leaves is water. At times, they also feed on the bark and buds of the eucalyptus trees. They usually spend 3-4 hours of the day feeding, while most of the remaining part of the day is spent resting.
Koalas are extremely choosy and fussy about their diet, and are well aware of the existence of all the various species of eucalyptus trees. As per statistics, there exists around 650 species of eucalyptus trees in the eucalyptus forests of Australia, but a koala's preference lies with just two or three of the species. They are not only particular about the species of eucalyptus tree leaves that they feed on, but their attention to detail is such that, they consume the leaves and buds only after they have reached a particular stage of maturation.
The species of eucalyptus tree chosen by the koala for feeding, also depends on the area of its habitat. Koalas residing in the southern region of Australia, prefer feeding on eucalyptus trees like the swamp gum and manna gum, while those residing in the northern areas, prefer species like blue gum, gray gum and red gum. Other favorite species of eucalyptus trees include yellow box, small-leafed peppermint, tallow wood, river red gum and drooping red gum.
Apart from eucalyptus leaves, koalas occasionally feed on wattle, paper bark, pine trees, cherry trees and tea trees. At times, they also climb down the trees to eat gravel and soil, to fulfill their requirement of minerals and help them to digest the eucalyptus leaves. Koalas hardly stay on ground and the moment they are done with the feeding, they climb back safely to their respective trees.
Eucalyptus leaves consist of approximately 13% tannins, 2% minerals, 50% water, 18% fiber, 8% fat, 5% carbohydrates and 4% proteins. They also contain toxic oils that are extremely poisonous to other animals, but, the Koala bears, the Greater glider and the Ringtail possums are the only three mammals that can survive on a eucalyptus leaves diet. It might seem surprising how koalas can survive on such a diet, but, nature has equipped them with extraordinary mechanisms that ensure their survival.
Their digestive system has specialized adaptations that detoxify the toxic oils in the eucalyptus leaves, and this detoxification process is also aided by their liver which produces glucuronic acid. Glucuronic acid enables koalas to quickly excrete all the toxins. Koalas also have an additional part in their digestive tract, known as the 'cecum', that breaks down the food further and aids in digestion. Koalas have a very slow metabolic rate, that allows them to retain food and energy for a longer period of time.