January 6, 2011
FeatureKoalas: Australia’s Pickiest Eaters
Koalas, one of nature's pickiest eaters, choose to only dine on eucalyptus leaves. (Photo credit: Purestock/Getty Images)
Many people have favorite foods. But one Australian mammal takes “favorite food” to the extreme—the koala (Phascolarctos cinereus). These marsupials have evolved to live almost exclusively on eucalyptus leaves. And if that isn’t picky enough, recent research suggests that koalas are highly selective as to the species of eucalyptus they prefer and even the individual trees from which they choose to eat. How have these animals become so picky, and how can scientists use this information to aid in koala conservation efforts?
Filling a NicheIn ecological terms, the highly-selective diet of the koala makes them a specialist, that is, a consumer that primarily eats one specific organism or a very small number of organisms. Specialist species are generally sensitive to environmental changes, especially changes that affect the availability of their food source. However, the pickiness of koalas is likely an evolutionary adaptation.
Eucalyptus trees are the dominant trees of Australia. In fact, there are more than 700 species in the genus Eucalyptus, and most are native to Australia. However, the leaves of these trees are actually very low in protein, not easily digested, and contain compounds that are toxic to most species. Therefore, the ability for koalas to specialize in eating eucalyptus leaves has allowed them to fill an ecological niche. Koalas have virtually no competition for their preferred food source.
Koalas spend approximately 18-20 hours each day sleeping, and most of the remaining time is spent eating. They eat about 500 grams of eucalyptus leaves each day. A number of adaptations allow koalas to digest this food efficiently:
- Powerful jaws allow the koala to chew the leaves into a very fine paste.
- The koala’s liver is able to deactivate the toxic compounds found in eucalyptus leaves.
- A portion of the koala’s large intestine is greatly enlarged to maximize the amount of nutrients extracted.
Recent research has focused on finding what characteristics of eucalyptus leaves make them tasty for koalas. In one study, scientists tested a variety of leaves on captive koalas and recorded how much they ate. By analyzing the chemical composition of the leaves that koalas preferred, these scientists found that koalas ate less when the leaves provided to them were high in certain chemicals called formylated phloroglucinol compounds, or FPCs.
The next step in this study was to track wild koalas in a eucalyptus woodland. The scientists found that they were able to use the taste preferences of the captive koalas, based on chemical composition, to predict the tree preference of wild koalas. In addition, the scientists found that koalas spent more time in larger trees that were surrounded either by smaller, less-tasty trees or by larger trees that were equally tasty. Using this combination of leaf chemistry, tree size, and spatial environmental data, scientists hope to map koala habitats based on habitat quality, as a koala would see it.
Scientists hope that research on koala habitat quality will provide useful insight for future conservation projects for the species. (Photo credit: Joseph Van Os/The Image Bank/Getty Images)
All of this koala habitat mapping may prove very useful as the concentration of carbon dioxide continues to increase in the atmosphere. Other laboratory studies have shown that increases in carbon dioxide cause the concentration of toxins or compounds that otherwise interfere with digestion in eucalyptus leaves to increase. By studying how increased concentrations of carbon dioxide would affect the chemical composition of various Eucalyptus species, scientists may be able to predict which areas contain habitat that would most likely be of high quality for koalas in the future, and work to protect these areas.
Comments
Comment from: Michelle
January 23, 2011 03:12 PM [#]
This article made me wonder how koalas would adapt to being placed in an entirely different environment with no Eucalyptus trees to feed on.
Comment from: Mary-Kate
January 24, 2011 09:33 PM [#]
In my opinion, there are several reasons the koala prefers eucalyptus leaves. One factor could be purely based on taste preference. Perhaps when given the leaves high in FPC, the chemicals did not taste as good as eucalyptus leaves. Since there are no other animals competing for the same food source, there should not be a problem with koala conservation. Even though these leaves are low in protein, the koala has intestines to maximize the nutrients taken from eucalyptus leaves. The abundance of the trees with the preferred leaves, has more than likely caused the koalas to learn to adapt to them and use them as the number one source of food.
Comment from: Lacey Kish
January 25, 2011 10:13 PM [#]
That is so funny how an animal that sleeps practically all day long, eats Eucalyptus leaves that do not have any value in nutrition, and have toxic compounds. They aren't even fat animals. How is this possible?
Comment from: Anonymous
January 27, 2011 08:43 AM [#]
koala seems more pickier than humans with there food. there food has to be the perfect thing.
Comment from: danielle
January 27, 2011 08:44 AM [#]
it so cute! :)
Comment from: Nathan Hall
January 27, 2011 01:34 PM [#]
I never knew that Koalas were so picky. The scientists who study this must have had to take a while just to find the right eucalyptus leaves.
Comment from: Kourtney
January 28, 2011 08:31 PM [#]
I never knew that Koalas only ate eucalyptus leaves. I just thougt that was their favorite. Also considering that all they basically do is eat and sleep, it's a wonder that their not fat.
Comment from: Julie Hubbell
January 29, 2011 03:28 AM [#]
It seems that koalas may just be the pickiest marsupials. I think testing and experimenting on the growth of Eucalyptus trees would be the most beneficial in keeping the koala population steady. Surely if they can grow potatoes above ground and pumpkins that weigh 1,000 lbs., then they can create a Eucalyptus tree that is heartier and can balance the chemicals.
Comment from: Tanner
January 29, 2011 03:29 PM [#]
i think it would be interesting to see what would happen if the eucalyptus plant died out or nearly did. would koalas just start to die or would they adapt and eat something else?
Comment from: Hannah Norman
January 30, 2011 03:10 PM [#]
i deffinately did not know that Koalas were such picky eaters. I could not just eat one leaf my whole like. It's crazy how they sleep 18-20 days but I wouldnt mind doing that sometimes. haha. It the leaf does not have enough nutricios how do the Koalas servive?
Comment from: Evan Mitchell
January 30, 2011 04:57 PM [#]
If theoretically the Eucalyptus species slowly became endangered, would koalas become endangered along with it? Or would the koalas adapt to another food source in the same way they did Eucalyptus?
Comment from: Joey Alarid
January 30, 2011 05:22 PM [#]
I'm wondering why koalas are so picky about what they eat. We think humans are picky with what we eat but really we eat a wide range of foods. Its crazy how koalas can find the perfect tree to get food from.
Comment from: Cassidy
January 30, 2011 07:23 PM [#]
I had no idea koalas only ate one thing, i would think the same thing would get boring after eating them your whole life, but they must be pretty good. I'll have to try some :) Also, it makes me wonder what would happen if the eucalyptus trees all of a sudden got a disease or something.. if the koalas would starve, or find something else.
Comment from: Sarah Langford
January 30, 2011 08:26 PM [#]
I wonder what the koala's would eat if there were no eucalyptus leaves.
Comment from: Jessica
January 30, 2011 09:56 PM [#]
It's insane that koalas only eat eucalyptus leaves, but it's even MORE insane that they eat only certain kinds of eucalyptus leaves. They are not skinny animals, so I don't understand how they stay so big while only eating the eucalyptus leaves.
Comment from: Mark
January 31, 2011 10:51 AM [#]
They r eventually going to have to find a new source of food since it will run out
Comment from: Wread
January 31, 2011 05:05 PM [#]
It's strange to think that if the koala population had to be relocated even if just 100 miles for conservation reasons it would endanger most If not all of the koala population
Comment from: Jamie
April 20, 2011 10:13 PM [#]
Intresting....It proves how important every organism is to the entire ecosystem, even the ones that seem not important.
Comment from: Anonymous
April 4, 2012 06:12 PM [#]
That was so helpful to get facts about koalas.
thank you