India’s Tiger Sanctuaries

Bengal tigers

As of 2014, the worldwide population of Bengal tigers numbered 2226. (Photo credit: Swapan Photography/Shutterstock)

Over a century ago, more than 100,000 Bengal tigers roamed India. Today, there are just over 2200. What caused such a drastic drop in numbers? And what can be done to save the Bengal tiger from extinction? [Read more…]

Madagascar’s Upside-Down Trees

(Photo credit: Gil.K/Shutterstock)

Madagascar is home to six of the world’s eight species of baobab trees. (Photo credit: Gil.K/Shutterstock)

The baobab is a tree with an unusual look. Many compare its appearance to a tree planted upside-down, as it looks like its roots are reaching toward the sky. [Read more…]

Australia’s Pickiest Eater

koala

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 the koala takes “favorite food” to the extreme. These Australian 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 Niche

In 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.

Studying Feeding Preference

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.

The Future of Koala Habitats

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.

More to Explore

The 411 on Fjords

(Photo credit: Stefan Auth/imagebroker RF/Photolibrary)

Fjords are a spectacular part of the Norwegian landscape. (Photo credit: Stefan Auth/imagebroker RF/Photolibrary)

Fjord is a Norwegian word describing a long, narrow inlet of water with steep cliffs on either side. Norway has the world’s highest concentrations of fjords. [Read more…]

The Mountain Gorillas of Rwanda

mountain gorilla

The mountain gorillas of Rwanda are the only primate species in the world that is growing in number, making this critically endangered species a success story.  (Photo credit: erwinf/Shutterstock)

The mountain gorillas of war-torn Rwanda are making a comeback. [Read more…]

New Zealand’s Iconic Kiwi Bird

(Photo credit: Tom McHugh/Getty Images)

While just over a century ago, kiwi birds numbered over 20 million, today New Zealand is home to less than 70,000 of these unique birds. (Photo credit: Tom McHugh/Getty Images)

The kiwi bird is such an important part of New Zealand culture that New Zealanders call themselves “kiwis.” But, while just over a century ago these birds numbered over 20 million, today there are less than 70,000. What has caused their population to drop so drastically and can anything be done to bring these unusual birds back from the brink of extinction? [Read more…]

The Revitalization of Monterey Bay

sea otter

Monterey Bay is well-known for its sea otter population. (Photo credit: worldswildlifewonders/Shutterstock)

It wasn’t all that long ago that the Monterey Bay was a gloopy mess and one of the most polluted places on the Pacific Coast. Today it is considered to be one of the most productive marine ecosystems on the planet. What changed? How did a once-neglected and degraded region become one of the most revered and studied ecosystems on Earth? [Read more…]

The Tree Goats of Morocco

goats in argan tree

These Moroccan goats have an important role in the extraction of argan oil, a precious commodity. (Photo credit: Yavuz Sariyildiz/Alamy)

While goats are well-known for their ability to jump over fences and scale great heights, a certain population of goats in southwestern Morocco takes their climbing skills to a whole new level. [Read more…]

Nepal’s Fragile Himalayan Ecosystem

Gokyo Lake, Nepal

The Himalayan mountains are an impressive part of the Nepal landscape. (Photo credit: Craig Kassover/National Geographic Society/Corbis)

Nepal is a top destination for trekking – nearly 43 percent of visitors to the country plan to partake in trekking activities. But what impact does trekking have on the country’s fragile Himalayan ecosystem? [Read more…]

Cameroon’s Mysterious Crater Lakes

(Photo credit: Harri's Photography/Flickr Open/Getty Images)

Though picturesque, some crater lakes hide a deadly secret. (Photo credit: Harri’s Photography/Flickr Open/Getty Images)

August 21, 1986 started out as a normal day near Cameroon’s Lake Nyos. By the end of the day, however, 1746 people and 3500 livestock in the area would be dead. The cause of the catastrophe was, of all things, an exploding lake. But what caused the lake to explode? More importantly, could it happen again? [Read more…]