What Do Koalas Eat and Drink?

The diet of the koala (Phascolarctos cinereus) is based on leaves from different trees of the genus Eucalyptus. Since they can subsist exclusively on the leaves of these plants, they are considered types of herbivorous animals. When foraging for leaves, koalas select the tree species that have a high protein content and low proportions of both fiber and lignin. This makes them a specialist folivore, having a preference for approximately 30 eucalyptus species, including E. microcorys, E. tereticornis, E. camaldulensis, and E. viminalis.

Eucalyptus leaves have a large percentage of water and also contain significant amounts of secondary metabolites. Some metabolites such as phenolic compounds and terpenes are usually poisonous to most mammals. The koala is a marsupial capable of detoxifying these compounds in their digestive system.

Koalas also have the ability to select plant material with a lower proportion of toxic secondary metabolites. This ability is due to numerous receptors in the vomeronasal organ and taste receptors that allow them to detect substances such as terpenes, phenols and glycosides. The low nutrient content of their food provides them with little energy.

Since the food they eat provides relatively little energy, they have to conserve much of it. They are only active for about four hours a day which is used for feeding and other necessary behaviors. The rest of the time they are usually at rest.

Although they prefer eucalyptus leaves, their diet is not only limited to this plant. They can occasionally ingest other plants from the myrtle (Myrtaceae) botanical family such as various tea trees (including genera such as Leptospermum and Melaleuca). They can also include foliage from species from other families such as those of the Acacia, Allocasuarina and Callitris.

Koalas primarily derive their hydration from the moisture present in the eucalyptus leaves they consume. We already know that eucalyptus leaves are the main component of a koala's diet and provide their food for sustenance, but they also generally cover their hydration needs. Not only do eucalyptus leaves have a high water content, but koalas have specialized adaptations to extract water from them.

Koalas have evolved to conserve water efficiently due to their dependence on eucalyptus leaves. Their low metabolic rate helps to do so and they can obtain sufficient water from the leaves they consume. Koalas rarely drink water directly. They are usually only known to drink from natural water sources such as puddles or creeks during times of extreme heat or drought when the moisture content in the leaves might not be sufficient.

Koalas in captivity, especially those in wildlife rehabilitation centers or zoos, might be provided with supplementary water to ensure their hydration needs are met. In the wild, koalas have evolved to rely on the moisture in eucalyptus leaves as their primary source of water.

Koalas have an oral cavity made up of incisor teeth, a single premolar and four molars in each jaw. Like many other herbivorous animals, they have a distinctive diastema. This is a space devoid of teeth between the incisors and the premolars and molars. It allows the koala to move the leafy vegetation around in their mouth more efficiently for mastication.

The incisors are used to pick up the leaves. They are cut along the petiole with the premolars before passing them to the molars and crushing them into smaller pieces. As they are marsupial animals, they can store the plant material in their pouches before being chewed. A well processed food produces a more efficient digestion of the stomach and a better absorption of nutrients in the intestine.

Koalas are considered gut fermenters due to the way their digestive systems are adapted to process the cellulose found in eucalyptus leaves. In intestinal fermenters, the food bolus passes through the main absorption sites before reaching the most important fermentation sites which are known as the cecum.

The koala cecum is very long and is proportionally considered one of the largest in the animal kingdom. This larger size increases the digestion of cellulose and prolongs the time available for digestion. Since they derive a low amount of energy from their diet, their metabolic rate is very low compared to other mammals. They are also able to conserve water by excreting dry, fiber-rich fecal matter and storing water in the cecum.

Now we know what koalas eat and drink, you may want to know some more facts about koala diet:

• They are marsupial mammals that are characterized by presenting a brief development in the uterus and completion of their initial growth in a specialized pouch called a marsupium. This is an epidermal sac that functions as an incubation chamber and contains the mother's mammary glands.
  
  
• They have a robust body, a large head and rounded and hairy ears. Their nose is large and their tail is short in length. They can measure between 24-33"/60-85 cm and weigh up to 33 lb/15 kg. Their fur is generally silvery gray in color.
  
  
• Adult males communicate through loud sounds that intimidate potential rivals and attract females. They are territorial and generally mark their presence in trees through secretions released from scent glands located on their chests.
  
  
• Three distinct subspecies of koala exist. They are the Queensland koala (Phascolarctos cinereus adustus), the New South Wales koala (P. c. cinereus), and the Victorian koala (P. c. victor). They differ by the color and thickness of their fur, their body size and the shape of their skulls.
  
  
• Koalas have been categorized as vulnerable according to the IUCN, due to the various threats they face. These include habitat destruction, fragmentation and modification, making them more vulnerable to predation by other animals, vehicle crashes, forest fires and diseases, among other factors.
  
  
• At present there is an international organization called the Australian Koala Foundation (AKF) whose main objective is the long-term conservation of koalas in the wild in Australia.

Discover more about another Australian mammal with our article on what are quokkas?

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