Jaw photos courtesy of University of Michigan Museum of Zoology.
Photo courtesy of The Koala Page.




Koala Teeth...


To make the most of the energy that is available in their diet, the koala utilizes a decreased metabolic strategy that allows it to retain food in its digestive tract for extended periods of time, thus maximizing the energy able to be extracted (Australian Koala Foundation). The highly specialized digestive organs of the koala are adapt at withdrawing the required nutrients from the poorly balanced diet. However, the digestion of eucalyptus leaves begans long before it reaches the primary digestive organs. The koala's teeth have also become highly specialized and are a crucial aspect of the digestive process. When discussing digestion, plant material can be divided into two components, cell wall and cell contents. Studies show that 91% of the koala's daily energy requirements are contributed to the extremely high digestion of cell contents (Lanyon and Sanson, 1986). The initial mastication or breakdown of food begins in the mouth where the teeth crush and shear food particles. This effectively increases the surface area and exposure of cell contents for the specialized digestive organs so they can meet the necessary nutritional requirements. Because solutes and fine particles are retained and become the primary source of the koala's energy, it is crucial that their teeth are efficient in the initiation of foliage breakdown.

Lower Teeth

Upper Teeth

The sharp front incisors of the koala are relatively sharp and are used to nip leaves from the brances of trees. Once the leaves are in the mouth, the are guided by the tounge to the large back teeth, or molars, that are specifically shaped to allow the koala to cut and shear the leaves, preparing them for further diegestion. There is a large gap, called a diastema, between the incisors and the molars that allows the tounge to efficiently move leaves around the mouth (Australian Koala Foundation). The koala's chewing motion is very interesting because there is an absence of a crushing component at the end of the occlusal stroke. The motion is characterized by a sliding of the jaws. The lower jaw moves in an anterior lingual direction. This causes the sharp grinding surface of the molars to slide past each other, exposing as much cell content of the leaves as possible (Lanyon and Sanson, 1986). So, the leaves aren't really crushed, they are repeatedly grinded and shreaded to be broken down and prepared for further digestion. It is very important that as much cell content as possible is exposed during mastication. The initial breakdown of foliage and exposure of cell content helps increase the efficiency of future digestive processes. Ultimately, efficient mastication influences the koala's ability to meet its metabolic needs given its poorly balanced diet.




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This page was created as an assignment for Animal Physiology at Davidson College. If you have any questions, you can e-mail me at cocrawford@davidson.edu.

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Front Teeth

Photo courtesy of The Koala Page.