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Green and black poison dart frog. (Photo by R. Butler)
OTHER GROUND ANIMALS
REPTILES
The most abundant vertebrate predators of the forest floor are reptiles, namely snakes and lizards. Best known of forest snakes are the giant constrictors, pythons of the Old World and Australasia, and boas of New World, but many of these are arboreal, aquatic, or relatively small. The majority of the snakes of the forest floor are small to medium sized, nocturnal, and mildly poisonous. They eat a range of amphibians, mammals, small birds, and insects. Very few of these species pose a threat to humans, although some are notorious for inflicting bites. The fer-de-lance viper of the New World, cobras of the Old World, and bushmaster of the New World are well-known examples.
There are several notable snakes of the rainforest with strange habits or characteristics. For example, the mole viper has long fangs that protrude beyond the corners of its mouth, while the African egg-eating snake, with its detachable jaw hinge, is specially adapted to feeding exclusively on bird eggs. This snake species is equipped with lower vertebrae that have an enamel-like coating and penetrate the esophagus to act as a saw-like structure. Although its head is about the size of a human finger, the African egg-eating snake can swallow eggs larger than that of a hen. One African snake species, sometimes labeled the "two-headed snake," has a tail that resembles its head, and a head that resembles a tail. In addition, to further confuse predators, the snake moves its tail in a manner that mimics the way most snakes move their heads. Thus if attacked, the tail (resembling the head) is the most likely target and the snake is much more likely to escape.
The komodo dragon of folklore would seem to be one of the largest, more formidable beasts on earth. However, in reality, many of the "facts" about the Komodo dragon are exaggerated. First of all, the komodo dragon is a lizard belonging to the group of 31 species of lizards known as monitors, found in the Old World. Secondly, the komodo dragon does not reach 30 feet (9 m) as reported by many, but the largest recorded specimen was just over 10 feet (3 m) in length—still an impressive size. The komodo dragon is found on a few scattered islands in Indonesia south of Celebes. With a belly full of deer, one may reach 500 pounds.
Chameleons, discussed in "Chapter 4: The Canopy" are actually most active near the ground. There are some 135 species of chameleons found in Africa, half of which are endemic to Madagascar (Malagasy chameleon pictures). These solitary lizards are well adapted to their surroundings with their well- known ability to change color, along with their large eyes which can be moved independently, and their meter-long tongue. Interestingly, chameleons often do not change color to match their surroundings, but instead to convey emotions, defend territories, and communicate with mates. At the height of the breeding season, colors are spectacular, as males try to impress females. At night, in a relaxed state, chameleons turn pale, almost white.
Another group of lizards from Madagascar is the fringed, leaf-tailed, or uroplatus geckos (pictures) which are incredible camouflage artists. Some species look exactly like bark, while others resemble moss when they flatten themselves against their surroundings. When discovered, uroplatus geckos respond by throwing their mouths wide open, showing the bright orange-red interior, and erecting their tails.
Geckos are found worldwide and are quite famous for their abundance and loud call. Numerous species are kept widely as pets, while house geckos are found in virtually every house in the tropics, where they feed on house insects.
AMPHIBIANS
Amphibians are common on the forest floor, although not as abundant as those of the trees. Among the best known of rainforest amphibians are the tiny but brilliantly colored poison dart (arrow) frogs (members of the Dendrobatidae family). These striking but slow-moving frogs secrete powerful toxins from glands on their backs and use their color to advertise their toxic composition to potential predators. The potency of the toxin varies according to the species, and rainforest dwellers have been using these skin secretions for centuries to poison the tips of their blowdarts. The most toxic frog known is the yellow-gold Phyllobates terribilis, of Western Colombia, which is said to be fatal if held in the hand. Indians need only rub and arrow tip across the frog's back and the arrow is good for a year. Other poison arrow frogs must be roasted to extract their poison. The skin secretions of poison arrow frogs have human healthcare applications as evidenced by the story of Epipedobates tricolor and ABT-594/epidatidine.
Not all rainforest frogs are so brilliantly colored. In fact more amphibians take the opposite approach to defense: camouflage. Several species throughout the world, including the horned toad and two unrelated frogs in Brazil, look like dead leaves and when disturbed stretch out their back legs and become totally still for 30 minutes.
Amphibians are on the decline worldwide—more than 20 are known to have gone extinct this century. Several notable species including Costa Rica's Golden toad (Bufo periglenes) and the Gastric Brooding Frog (Rheobatrachus silus) of Queensland, Australia, have disappeared in recent decades. Scientists are puzzled over what is responsible for species loss among amphibians; some speculate that environmental degradation [habitat loss, climate change, increased UV levels from ozone depletion] has weakened populations to the point of making them more vulnerable to parasites, chytrid funges, ranavirus, and deformities. Because amphibians have highly permeable skin and spend a portion of their lives in water and on land, they are sensitive to environmental change and can act as the proverbial canary in a coal mine, indicating the relative health of an ecosystem.
A photo sampling of rainforest herps (reptiles and amphibians)
Extinct goat was "similar to crocodiles"
(11/16/2009) It sounds like something out of Greek mythology: a half-goat, half-reptilian creature. But researchers have discovered that an extinct species of goat, the Balearic Island cave goat or Myotragus balearicus, survived in nutrient-poor Mediterranean islands by evolving reptilian-specific characteristics. The goat, much like crocodiles, was able to grow at flexible rates, stopping growth entirely when food was scant. This adaptation—never before seen in a mammal—allowed the species to survive for five million years before being driven to extinction only 3,000 years ago, likely by human hunters.
DNA uncovers nearly extinct Siamese crocodiles in captivity
(11/15/2009) The Critically Endangered Siamese crocodile, once believed to be extinct in the wild, received some uplifting news this week. DNA testing of 69 rescued crocodiles at Phnom Tama Wildlife Rescue Center (PTWRC) in Cambodia found 35 purebred Siamese crocodiles.
Reptiles underrepresented on the IUCN Red List
(11/04/2009) Currently there are an estimated nearly 9,000 reptiles in the world, while the International Union for Conservation of Nature (IUCN) Red List has assessed all of the world's described mammals, birds, and amphibians, reptiles have yet to be fully assessed, leaving herpetologists with an unclear picture of how reptiles are faring in the world. Currently, 1,677 reptiles have been assessed (less than 20 percent of the total number of reptile species known) with 293 added this year.
The Yangtze River may have lost another inhabitant: the Chinese paddlefish
(10/22/2009) In December of 2006 it was announced that the Yangtze River dolphin, commonly known as the baiji, had succumbed to extinction. The dolphin had survived on earth for 20 million years, but the species couldn't survive the combined onslaught of pollution, habitat loss, boat traffic, entanglement in fishing hooks, death from illegal electric fishing, and the construction of several massive dams. Now, another flagship species of the Yangtze River appears to have vanished.
Scientists uncover mystery of how frog plague kills its victims
(10/22/2009) One hundred and twenty species of frogs are reported to have gone extinct since 1980 (although the number is likely even higher). While devastated by habitat loss, pollution, and climate change, a baffling disease may be the biggest factor behind the alarming extinctions of frogs. Called chytridiomycosis, the disease is caused by the microscopic fungus Batrachochytrium dendrobatidis which kills its tiny victims indiscriminately.
