Environmental Science News at Your Fingertips
Monarch butterflies cluster tightly together in pine and fir trees in their Mexican habitat. (Photo credit: Getty Images)
The number of monarch butterflies overwintering in Mexico dropped by 27 percent in 2017, according to experts. This decline is a reversal in last year’s numbers, which appeared to show a recovery in the monarch butterfly population. [Read more…]
Sloths are found throughout Costa Rica’s tropical forests. (Photo credit: Kjersti Joergensen/Shutterstock)
With their shy, seemingly secret-hiding smiles, languid movements, and unique habits, the sloth fits the basic description of a charismatic animal to a T.
These unusual animals can be found in the tropical forests of Central and South America. Their populations are flourishing in their Costa Rican habitat. Sloths can be found in ecosystems throughout this Central American country, except at the highest elevations.
There are two species of sloth found in Costa Rica: Bradypus variegatus, commonly known as the three-toed sloth, and Choleopus hoffmanni, commonly known as the two-toed sloth. Both of their scientific names reflect their slow movement, as Bradypus means “slowness of foot,” and Choleopus means “lameness of foot.” Though they look similar to primates, sloths are actually more closely related to anteaters and armadillos.
Though it was commonly thought that sloths spent most of their time sleeping–previous estimates had sloths spending upwards of 14 hours asleep per day–research from 2008 indicates that these animals actually only sleep 9 to 10 years a day. Scientists think the previous estimates, based on captive populations, overestimated the sloths’ sleep patterns as those sloths lacked the need to be vigilant against predators. In the wild, three-toed sloths are active both day and night, while two-toed sloths are nocturnal.
These animals spend the majority of their lifetimes in the tops of trees. Their slow movement is likely a result of their need to conserve energy due to their extremely slow metabolism. It takes a sloth up to four weeks just to digest a single leaf. Contrast that with humans, who completely digest a meal within a period of 24-44 hours. One of a sloth’s more unique habits is a result of its slow digestion–sloths only relieve themselves once a week. To do so, they climb down to the bottom of the tree where they do their business, losing about 1/3 of their body weight in the process.
One thing that helps sloths avoid predators and blend in with their leafy habitat is the algae that grows on their fur. The species of algae that lives within sloth fur is Trichophilus welckeri, which is found nowhere else. Research indicates that the algae is passed from mother to offspring within a few weeks of its birth. However, a sloth’s fur isn’t just a habitat for algae. It also houses a variety of other insects and fungi. One of the more interesting examples is the pyralid moth (Cryptoses spp.), which relies on the sloth for its entire lifecycle. A sloth’s body could be home to more than 100 moths. The moth spends the majority of its lifetime burrowed deep within the sloth’s fur. The real magic happens when the sloth descends to the base of its tree to do its weekly business. The moths are coprophagous, meaning they eat excrement. Female moths lay their eggs in the sloth’s excrement, and the larvae grow to maturity within the dung before hatching and flying up the tree to find another sloth’s furry back to inhabit.
According to reporting in The New York Times about this phenomenon, “After [the moths] die, their bodies are decomposed by the host of fungi and bacteria in the sloth’s fur. The metabolic products of this decay, especially nitrogen, are the feedstock for the specialist algae that grow in the sloth’s hair shafts. The researchers guessed that the sloths might be eating the algae from their own fur, and that this could be the purpose of the whole system.”
In addition to being unique animals, it appears that the sloth itself is home to a unique ecosystem as well.
More to Explore
Sloth Facts: Habits, Habitat & Diet
National Geographic: Sloth
7 Surprising Sloth Facts
The Sloth’s Busy Inner Life
Solar power is just one aspect of Sweden’s sustainable development initiatives. (Bohner Images/Getty Images)
Sweden has consistently been ranked as one of the most sustainable countries in the world for several years in a row. How has this Scandinavian country embraced sustainable living? [Read more…]
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 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…]
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:
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.
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…]
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…]
Geothermal energy is a significant part of Iceland’s renewable energy program. (Photo credit: naten/Shutterstock)
Iceland is known for its dramatic fire and ice landscape. Visitors come from all over the world to soak in the island nation’s thermal pools, which are heated naturally by underground plumes of magma. However, this geothermal energy is harnessed for more than just recreational purposes – it is also used as an important source of renewable energy in the country and even beyond its borders. [Read more…]
Gwynt y Môr is the second largest offshore windfarm in the world. (Photo credit: philipbird123/Fotolia)
Gwynt y Môr (which translates to “wind of the sea” in English) is the second largest offshore wind farm in the world. It is located about 13 kilometers (8 miles) off the coast of north Wales near Colwyn Bay and covers an area of 80 square kilometers (about 30 square miles). [Read more…]