Marvels of Madagascar

Madagascar, the fourth largest island in the world, one and a half times the size of California, is home to amazing animals found nowhere else on the planet. In fact, thanks to millions of years of isolation from the rest of the world, around three-fourths of its species are endemic—occurring naturally only in Madagascar. The most widely known of these are lemurs.

However, Madagascar has also, for well over a century, been home to political unrest and social upheaval, as shown in last year’s coup. This turmoil has threatened the country’s unique forests and their inhabitants, pushing species to be endangered at best, and to extinction at worst.

The cause of Madagascar’s amazing animal diversity is rooted in its ancient history. One hundred and sixty million years ago (during the Jurassic period), Madagascar started breaking off from the landmass of Africa. Since then, it has made its way to the Indian Ocean, where it is separated by about 300 miles of ocean from the southeastern coast of Africa and virtually isolated from the world. Isolated areas, whether separated by insurmountable mountains or vast stretches of ocean, present opportunities for unique animals to evolve. Separating a population of animals means their genes can’t mix with other populations, causing them to develop down their own unique path. And, they can be safe from potential predators or competitors that may wipe them out in other places. Given ages of geologic time, island animals can become quite unusual, looking and behaving very differently from their distantly-related land-bound cousins, if the cousins are still around at all.

One question scientists have long been trying to answer is: How did the ancestors of the modern-day Madagascar animals have their start on the island? Treasure troves of unique fauna are not unusual on islands. However, when Madagascar first broke away from Africa, no animals, according to fossil evidence, were on the island that could have been the predecessors of the modern-day inhabitants. Their ancestors must have arrived later.

Although Madagascar is quite far from the African coast (270 miles at the closest point, about the distance from Santa Barbara to San Jose), in February, Jason Ali (University of Hong Kong) and Matthew Huber (Purdue University) reported in the journal Nature that around 20 to 60 million years ago, swift currents may have been just right to deliver terrestrial animals (clinging to floating debris for their dear lives, no doubt) from the African coast to Madagascar in only 25 to 30 days. Genetic evidence suggest that during this time mammals made their way to the island in four separate events, forming the basis for the four main mammal groups now on the island: lemurs, tenrecs, carnivores, and rodents. Around 20 million years ago these currents changed, isolating the island from further arrivals.

Living Lemurs: Lemurs, the most unusual group of animals on the island today, were the first to arrive, some 50 to 60 million years ago. Although they look like a squirrel crossed with a cat, lemurs are actually an ancient group of primates. Similar to monkeys, lemurs form social groups, have diverse diets, live in a variety of ecosystems, and come in a variety of shapes, sizes, and colors.

Elsewhere in the world, ancestors of the lemurs were long ago driven to extinction by monkeys, which came onto the evolutionary stage around 17 to 23 million years ago. Monkeys never made it to Madagascar—saving the lemurs, although today they face other threats. Most lemurs are endangered or threatened and many species have become extinct, mainly due to habitat loss from logging as well as hunting.

Though it’s often debated, it’s thought there are around 88 species, though many have gone extinct and new species are often discovered. Giant lemurs the size of gorillas once roamed Madagascar, but became extinct around 500 years ago. The largest lemur (Archaeoindris fontoynonti) weighed 350 to 440 pounds and reached five feet tall. Another group of stocky lemurs (genus Megaladapis) looked like giant koalas, at four to five feet tall with some weighing as much as 190 pounds. The largest lemur alive today is much smaller; indri (Indri indri) weigh around 15 pounds.

At 11 to 14 pounds and up to three and a half feet long, the silky sifaka (Propithecus diadema candidus), one of the largest lemurs, was recently highlighted in the Smithsonian magazine. The highly social silky sifaka is an amazing all-white lemur that rapidly dances through the forest treetops of Madagascar. But due to hunting and forest clearing, there are fewer than 1,000 still remaining, and possibly as few as 100.

The smallest lemurs (and also the smallest primates) belong to the group of dwarf and mouse lemurs (family Cheirogaleidae). With a long fluffy tail, the largest members of this group can reach 11 inches, while the smallest, the pygmy mouse (Microcebus myoxinus), can be less than five inches long and weigh one-fifteenth of a pound. These tiny primates can be quite elusive to study, especially since their territory is dwindling. Just last week the discovery of a potentially new giant mouse lemur species in a threatened forest was reported by the WWF (World Wide Fund for Nature).

Tiny Tenrecs: Another group of tiny mammals unique to Madagascar is the tenrecs (of the family Tenrecidae), which arrived around 25 to 42 million years ago. Looking like shrews or hedgehogs, tenrecs are most closely related to the golden moles and Elephant shrews of Africa. Tenrec species live in a variety of ecosystems on the island. The smallest can weigh as little as five grams, while the largest, the common tenrec (Tenrec ecaudatus), can weigh up to five and a half pounds. The greater hedgehog tenrec (Setifer setosus), as its name implies, much resembles a hedgehog.

Meat-Eating Mammals: The mammalian carnivores of Madagascar all descend from a common ancestor that arrived around 19 to 26 million years ago. These carnivores, eight species all in the family Eupleridae, while found only in Madagascar, are closely related to mongooses. The fossa (Cryptoprocta ferox) is the largest (weighing 22 to 26 pounds) and best known; it looks like a cross between a dog and a puma. The fossa and the much smaller five-pound striped civet, or Fanaloka (Fossa fossana), are thought to be the most ancient mammalian predators of the island. While there are many other known mammalian carnivores on the island, overall much is unknown about these predators.

Giant Jumping Rodents: The last mammalian group to arrive to Madagascar was the rodents, floating in some 20 to 24 million years ago. One fascinating endemic rodent is the Malagasy giant rat (Hypogeomys antimena), or the giant jumping rat. While it has the size and body of a rabbit, equipped with long pointed ears and hind legs for jumping, its face and tail resemble a rat’s. But it is quite unlike typical rats and rabbits in many ways; it only has one or two young a year, which it spends several years raising, and is monogamous. Due to hunting by introduced predators and habitat loss, it is predicted to go extinct within the next 24 years. Other endemic rodents face a similar fate.

Reptiles, Birds, Insects, and Plants: Many unique reptiles, birds, insects, and plants have also evolved on Madagascar. Madagascar is home to many brightly colored, poisonous frogs (99 percent of which are endemic) as well as half of all the chameleon species in the world. Nearly half of the birds on Madagascar (115 species) are also endemic. Now extinct, the world’s largest bird once lived on the island; flightless elephant birds (genus Aepyornis) stood ten feet tall, weighed around 1,100 pounds, and laid eggs just over a foot long. The Madagascar hissing cockroach, a two- to three-inch long cockroach distinguished by its size and hiss, is endemic to Madagascar and commonly sold as a pet in the U.S. All these unique animals also live among unique flora; 90 percent of all plants on Madagascar are found nowhere else.

There is debate over when, and from where, people first arrived on Madagascar. It’s thought that the first humans arrived nearly 2,000 years ago from Southeast Asia and Africa. Over time, different kingdoms were created on different parts of the island. Around 800 A.D., Arab merchants began trading with the inhabitants. But Madagascar remained unknown to Europeans until the 1500s, after which merchants from several European countries attempted, but failed, to create trading settlements on the island. During this time, Europeans reported seeing elephant birds on the island, although they became extinct in the following centuries. The giant lemurs of Madagascar, which had significant population declines since the arrival of humans, finally became extinct around this time. Both extinctions were mainly caused by habitat destruction and hunting.

By the early 1800s, Madagascar had become mostly unified, though this was followed by much social upheaval during the reign of Ranavalona I “the Cruel” and the invasion of Madagascar by France in 1894. This lead to Madagascar’s becoming a colony of France. Despite several bloody uprisings, one leading to the death of 80,000 natives, Madagascar did not win independence until 1960. Since then, the country has undergone incredible political instability and economic decline. But some hopeful events have happened. In 2001, President Marc Ravalomanana was voted into power on a platform of conservation, science, and foreign investment. Drastic action was needed; by this time, 90 percent of the island’s original forests had been cut down. Ravalomanana had more national parks established, and tourists and scientists alike came to see the natural scenic beauty, the amazing biodiversity, and the array of lemurs, helping to improve the damaged economy.

However, the decline of the global economy significantly hit Madagascar in early 2009. Tourism had declined, people were starving, and organized crime went on the rise. When Ravalomanana leased half of the cultivatable land to a Korean company, the capital city’s major, Andry Rajoelina, rallied opposition against Ravalomanana; consequential mob-related chaos resulted in around 200 deaths as foreign scientists fled the country. When Ravalomanana resigned, Rajoelina became president in March of 2009. The turmoil greatly affected tourism, hurting the economy even more.

Rosewood logging was made legal at the beginning of this year, leading to the logging of thousands of tons of rosewood. Although the ban on rosewood logging was reinstated on March 25 in response to global outcries, logging, mining, slashing-and-burning of forests to create rice fields, and hunting remain significant threats for the biodiversity of the island. Many protections need to be put in place to ensure that these animals and plants will be alive in the near future.

For a close-up experience with some animals native to Madagascar, visit the Santa Barbara Zoo, which harbors not only Madagascar hissing cockroaches but several highly endangered black and white ruffled lemurs (Varecia variegata), most of them born at the Zoo during the past few years.

For more on the amazing biodiversity on Madagascar, see Jason Ali and Matthew Huber’s article in Nature on Mammalian biodiversity on Madagascar controlled by ocean currents, the Smithsonian’s recent article on the Silky Sifaka, the WWF’s recent article on a newly discovered population of giant mouse lemurs, the Smithsonian’s National Zoological Park’s website on Lemurs, the website of WildMadagascar.org, Wikipedia’s article on Madagascar, or Joseph F. Merritt’s book Mammalogy: Adaptation, Diversity, and Ecology.

Biology Bytes author Teisha Rowland is a science writer, blogger at All Things Stem Cell, and graduate student in molecular, cellular, and developmental biology at UCSB, where she studies stem cells. Send any ideas for future columns to her at science@independent.com.