Lizards and snakes ... oh, my! The American Museum of Natural History is the ideal showcase for live squamates and their remarkable adaptations for survival, including projectile tongues, deadly venom, amazing camouflage, and sometimes surprising modes of locomotion.
The exhibition includes four species of geckos in a case equipped with cameras located in two different viewing stations that allow onlookers to zoom in on the creatures. There also is a Web camera mounted on the Water Monitor case, enabling virtual visitors around the globe to observe the daily life and routine behavior of one of the largest living species of lizard on Earth.
"'Lizards & Snakes: Alive!' brings science to life by inviting visitors to meet and mingle with some of the world's most exotic and fascinating creatures," notes Ellen V. Futter, president of the American Museum of Natural History. "These small--and sometimes terrifyingly large--ambassadors from the natural world teach us about the glorious diversity of life, the fragility of natural systems, and our own responsibility to study and steward life on Earth."
"'Lizards & Snakes: Alive!' dispels many mistaken notions," points out exhibition curator Darrel Frost. "For instance, snakes are not slimy and are just an [incredibly] successful group of lizards that have lost their legs. Visitors to this exhibition will learn about the amazing diversity of squamates--a group composed of roughly 8,000 known species of lizards and snakes--and how they have evolved into many shapes and sizes and have come to live in so many habitats."
"Our fascination with lizards and snakes starts early and endures throughout life," adds Michael Hager, executive director of the San Diego Natural History Museum. "'Lizards & Snakes: Alive!' is a great family exhibition where curiosity about nature is nourished. Teaching careful observation and learning about fascinating strategies for survival are key ingredients in the development of careers in science."
The exhibition examines many aspects of squamates, including differences in hunting techniques. One group, the "sight hounds"--consisting of about 1,400 species, including iguanas and their relatives--like humans, relies mostly on vision, not smell, to find their dinners and mates, and uses their tongues to capture food. The "nose hounds'--a large group containing monitors, skinks, and snakes--on the other hand, employ a highly evolved chemo-receptive system that collects chemical clues from the environment with forked tongues and delivers them to special sense organs on the roofs of their mouths. Another focus is how snakes, among the most evolutionarily successful vertebrates on Earth, have compensated for the absence of limbs with thermal vision, complex venom-delivery systems, constriction, and expandable jaws that give them the ability to swallow prey many times larger than their own heads.
"Lizards & Snakes" also offers numerous interactive stations, inviting museum-goers to listen to recorded squamate sounds, test their knowledge about these creatures, explore the inner workings of a rattlesnake on the hunt, and view videos. An activity center for children encourages youngsters to, among other things, match lizards to their habitats, assemble squamate skeletons, touch skin casts, enjoy puzzles, and play science-related games.
Fossil specimens and casts are on view as well. Among the highlights is a fossil cast of Megalania, the largest-known terrestrial squamate, which attained lengths of up to 30'. This ancient relative of today's Monitor Lizards lived in Australia during the Pleistocene era (from 1,600,000 to 40,000 years ago).
Text panels throughout the exhibition discuss a range of topics, from different methods of catching prey to various forms of defense to squamate relationships. A 16' x 2' panel displays a cladogram--a diagram that groups animals by common ancestry. It notes that scientists still do not know where snakes belong in the tree of life, underscoring the dynamic nature of science. Close-up photography and high-definition video also reveal the extraordinary world of squamates.
"Lizards & Snakes: Alive!" is on view at the American Museum of Natural History, New York, through Jan. 7, 2007. The exhibition then can be seen at the Fernbank Museum of Natural History, Atlanta (Feb 10, 2007-Aug. 12, 2007) and the San Diego Natural History Museum (Oct. 16, 2010-April 3, 2011).
HALL OF REPTILES AND AMPHIBIANS
The American Museum of Natural History's Hall of Reptiles and Amphibians offers a rich context to present the exhibition, "Lizards and Snakes: Alive!" Located on the Museum's third floor, it explores details of the anatomy, defense, reproduction, feeding behavior, life histories, locomotion, and global distribution of reptiles and amphibians, the first vertebrates to live on land. Visitors can view a great range of these animals' physical forms, from the tiniest toads to fearsome crocodilians, and learn more about their diverse habitats and lifestyles.
At the entrance, onlookers encounter a Galapagos Tortoise specimen and a gape-mouthed American Crocodile across from a similarly toothy American Alligator, affording an opportunity to compare their anatomy. Deeper in, highlights include a group of 10' Komodo Dragons, with one specimen stretching its jaws across the belly of a wild boar. The group of Komodo Dragons, the largest and most ferocious lizards in the world, was brought to the Museum from a 1926 expedition to the Indonesian island of Komodo. These predatory--yet endangered--hunters can weigh as much as 200 pounds.
Additional specimens include a 25' Reticulated Python prepared to strike a wild chicken, or junglefowl. In another case are two Leatherback Sea Turtles, the world's largest turtle, one of which is laying eggs in the sand. Leatherback Sea Turtles must come to land to nest, but otherwise live their lives in water. Females come ashore at night in the late spring or summer to deposit some 80 to 100 eggs above the high-tide line. Large skeletal specimens are used to explore features of reptilian anatomy further.
The diversity of reptiles' reproductive strategies is featured in an exhibit that details such behaviors as territoriality, courtship, and mating. Highlights include two Western Diamondback Rattlesnake specimens mounted in a "combat dance" that typically occurs during breeding season. During such dances, males try to throw loops around one another and then firmly press or throw opponents to the ground.
There also is information on venomous snakes and specimens found in the U.S.--including the Eastern Diamondback Rattlesnake, Copperhead, and Cottonmouth--and beyond, such as the Fer-de-Lance, Puff Adder, Indian Cobra, and Habu. World maps show the distribution of venomous land and sea snakes. Most American species either lack venom or have venom that basically is harmless to humans. Nonetheless, this exhibit allows visitors to learn about the chemistry of venom and how to avoid snake bites.
Rhinoceros Iguana (Cyclura cornuta) occur on Hispaniola and neighboring islands where they live mostly on cactus fruits, flowers, and other plant matter. Courtship occurs during a single two-week period each year, during which the male waits patiently for the female to emerge from her burrow so he can attempt to impress her by bobbing his head and displaying his strength. This drama may repeat itself over the course of several days before he wins her over.
Collared Lizards (Crotaphytus collaris), which live in the central and western U.S. and northern Mexico, run on powerful hind limbs. In short bursts, they are about as fast as humans in full sprint. These lizards gape and flash the black lining of their throats when threatened.
Green Basilisks (Basiliscus plumifrons), found in Central America, sprint across the surfaces of streams when startled. They accomplish this with the help of fringes that increase the surface area of their toes and by churning their legs to create pockets of air to avoid being pulled down into the water. To manage a feat like this, a 175-pound human would have to maintain a speed of 65 mph.
Chuckwallas (Sauromalus ater), found in Mexico and the southwestern U.S., wedge into small crevices and expand for a tighter fit when threatened.
Western Fence Lizards (Sceloporus occidentalis) or one of its relatives--about 130 species in all--can be found in nearly every habitat in North and Central America.
Cuban Knight Anoles (Anolis equestris) live on branches of mango and palm trees in Cuba. Their large heads deliver a powerful bite that can subdue a wide variety of prey, including frogs, but they also eat fruit such as figs. Like other anoles, they can change color from brown to green and back; these creatures turn green for their aggressive displays.
Eastern Water Dragons (Physignathus lesueurii) and their relatives have permanent teeth fused to their jaws, unlike most lizards, whose teeth periodically are replaced. Indigenous to eastern Australia and southern New Guinea, they live in trees near water and will drop from great heights into water when disturbed.
Frilled Lizards (Chlamydosaurus kingii), to look menacing, expand a thin fold of skin that pops out around their necks like an automatic umbrella. The frill, which usually hangs like a cape, can be one foot across when erect.
Veiled Chameleons (Chamaeleo calyptratus), native to the southwestern Arabian Peninsula, have special cells in their skin that facilitate rapid and complex color-pattern changes, used to communicate with other individuals and for camouflage.
Madagascan Giant Day Geckos (Phelsuma madagascariensis), along with other geckos, can hang from ceilings and sleep on tree trunks without falling. Their secret is in the millions of tiny hair-like structures on their broad toe pads. These are so small they use molecular-level forces to adhere to surfaces, even those as smooth as glass.
Common Leaf-tailed Geckos (Uroplatus fimbriatus) have the distinction of having more teeth than any other amniote (terrestrial vertebrate). Their fringes, coloration, and flattened body help conceal them from predators in the rain forests of Madagascar.
Lined Leaf-tailed Geckos (Uroplatus lineatus) are solid yellow by day and chocolate brown with yellow stripes at night. Like closely related species, the females hold their eggs with their hind legs until they harden, and then hide them in the leaf litter.
Henkel's Leaf-tailed Geckos (Uroplatus henkeli), both male and female, have dramatically different color patterns. The males are yellow with large brown spots and the females are beige-gray with fine speckling.
Crested Geckos (Rhacodactylus ciliatus), known only from New Caledonia, 1,000 miles east of Australia, had been thought to be extinct until they were rediscovered in 1994. Unlike most geckos, they will eat fruit.
Tropical Girdled Lizards (Cordylus tropidosternum), found in eastern Africa, are protected by two layers of heavy-duty body armor. They give birth to live young as opposed to laying eggs like many of their relatives.
Blue-tongued Skinks (Tiliqua scincoides) scare away predators by sticking out their brightly colored tongues and hissing. These relatively slow-moving skinks bear live young as opposed to laying eggs like many related species.
Gila Monsters (Heloderma suspectum) are one of only two highly venomous lizards. Venom is channeled through special grooves in their teeth and, when mixed with saliva and the blood of their prey, kills or disables victims. Their venom has components that are being studied for diabetes treatment.
Water Monitors (Varanus salvator), indigenous to southeastern Asia and Indonesia, are consummate omnivores, able to eat even toxic Marine Toads without ill effect. One of the most economically important squamates, millions are killed each year for their meat and hides.
Green Tree Monitors (Varanus prasinus), native to Australia and New Guinea, spend most of their time in trees. They climb easily, gripping with their long toes and claws and using their long, flexible tails as a sort of fifth limb.
Emerald Tree Boas (Corallus caninus), found in the Amazon basin, have multiple highly sensitive heat-sensing organs that they use for 3-D thermal imaging of prey. They are strikingly similar--in color pattern and in the way they drape themselves on branches--to the Green Tree Python from Australia and New Guinea.
Amazonian Tree Boas (Corallus hortulanus), like the Emerald Tree Boa, grab and hold their prey with long teeth while squeezing their victims with their constricting coils. Some of these snakes have more than 200 teeth, which regenerate continually throughout their life.
Gabon Vipers (Bitis gabonica) have huge fangs, almost three centimeters long in adults, that rotate to a flat position when the snake's mouth is closed. When the snake gapes to strike, the bone to which the fangs are attached rotates, erecting the fangs. Because of their colorful pattern, they virtually are invisible on the forest floor.
Eastern Green Mambas (Dendroaspis angusticeps) are slender, fast-moving snakes that live in the treetops, where their vivid green color is good camouflage. Eastern Green Mambas are highly venomous but not as aggressive as often reported. They eat rodents, bats, and birds.
Red Spitting Cobras (Naja pallida), found in eastern Africa, are able to spit venom into the eyes of potential predators from as far away as six feet. Little is known about them except that their diet consists primarily of frogs.
Campbell's Milk Snakes (Lampropeltis triangulum campbell) are harmless and stay safe by imitating the coloration of the highly venomous Coral Snake.
Burmese Pythons (Python molurus) have beautifully patterned skin that helps them blend into the shadows of the forest floor but also threatens their survival. Pythons are hunted for their hides, which are used to make clothing and accessories. Females are more at risk; larger than males, they can reach up to 23' in length.
FACTS ABOUT SQUAMATES
* Squamates are a diverse group of legged and legless lizards, including snakes. There are nearly 8,000 species.
* They vary drastically in size and weight: the smallest living squamate, the Virgin Islands Dwarf Sphaerodactylus, is about one inch long and weighs less than one-tenth of an ounce, while the largest living squamate, the Komodo Dragon, has been known to reach about 10' in length and weigh more than 350 pounds.
* The longest known squamate, a fossil called Mosasaurus, was about 56' long and probably weighed around 35,000 pounds.
* At almost 30' long, the fossil of the giant Madtsoia indicates it was big enough to have eaten a horse.
* Squamate fossils have been found on every continent.
* Chameleons have tongues longer than their bodies that can shoot out at an insect at speeds of up to 16' per second; their turreted eyes can look in two different directions at once.
* Many geckos have a clear lower eyelid that is fused closed. They use their tongue to "wash" this "window."
* Many squamates have a third "eye." This hole in the skull between the eyes does not form images, but allows light to reach an organ in the brain, probably helping them respond to seasonal changes in length of day.
* The Emerald and Amazonian Tree Boas from South America have 3-D infrared vision to see their prey better while hunting at night.
* Many squamates have five toes on each hand and foot, while some have fewer, or none at all.
* Because the Banded Gecko's ears are positioned below its skull, you can shine a light on one side of its head and see it on the other.
* Snakes do not have real ears; instead, they pick up vibrations with their lower jaw to "hear."
* Humans and giraffes have seven neck vertebrae, while many squamates have eight. Some fossil lizards have as many as 19, including the fossil "relatives" of Platecarpus.
* The Common Leaf-tailed Gecko has over 300 teeth, more than any other amniote--a group made up of reptiles and mammals.
* Gabon Vipers have the longest fangs of any living snake: they can be nearly two inches tall.
Diet and Defense
* To scare potential predators, the Western Hooknose Snake draws air into a vent at the base of its tail and blows it out, causing a loud "pop."
* Reticulated Pythons can eat a human.
* Red Spitting Cobras can shoot venom into a person's eyes from as far away as six feet.
* The Gila Monster and the Bearded Lizard are the only two known venomous lizards; their relatives first possessed venom some 80,000,000 years ago.
* Some squamates--like Plate-carpus and the Campbell's Milk-snake--have rows of long, sharp teeth on the roofs of their mouths to help swallow prey and keep it from escaping.
* Venomous snakes do not always inject venom when they bite. These so-called "dry bites" actually are quite common.
* Some lizards have mildly toxic green blood that deters predators with its bad taste.
* Basilisks can run on water with the help of fringes that increase the surface area of their toes. By churning their legs to create pockets of air in the surface of the water, they seemingly defy gravity.
* A number of squamates can "fly." The Paradise Tree Snake flattens its body to create a more aerodynamic shape and is able to change direction in mid-flight.
* Some squamates can stick to glass, ceilings, and other smooth surfaces. The toes of geckos, anoles, and various skinks have toe pads with microscopic filaments that are so tiny they are able to form weak bonds with the molecules of these smooth surfaces.
SEEING THE SERPENT
The ability to spot venomous snakes may have played a major role in the evolution of monkeys, apes, and humans, according to a new hypothesis by Lynne Isbell, professor of anthropology at the University of California, Davis.
Primates have good vision, enlarged brains, and grasping hands and feet, and use their eyesight to guide reaching and grasping. Scientists have thought that these characteristics evolved together as early primates used their hands and eyes to grab insects and other small prey, or to handle and examine fruit and various foods.
Isbell instead suggests that primates developed good close-up eyesight to avoid a dangerous predator--the snake. "A snake is the only predator you really need to see close up. If it's a long way away, it's not dangerous."
Neurological studies by others show that the structure of the brain's visual system does not actually fit with the idea that vision evolved along with reaching and grasping, but the visual system does seem to be well connected to the "fear module," brain structures involved in vigilance, fear. and learning.
Fossils and DNA evidence show that snakes likely were the first serious predators of modern mammals, which evolved about 100,000,000 years ago. Fossils of snakes with mouths big enough to eat those mammals appear at about the same time. Other animals that could have eaten our ancestors, such as big cats as well as hawks and eagles, evolved much later. Venomous snakes evolved around 60,000,000 years ago, raising the stakes and forcing primates to get better at detecting them.
"There's an evolutionary arms race between the predators and prey," Isbell explains. "Primates get better at spotting and avoiding snakes, so the snakes get better at concealment, or more venomous, and the primates respond." Some primate groups less threatened by snakes show fewer signs of evolutionary pressure to develop better vision. For example, the lemurs of Madagascar do not have any venomous snakes in their environment and, in evolutionary terms, "have stayed where they are," Isbell reports.
In South America, monkeys arrived millions of years before venomous snakes, and show less specialization in their visual system compared with Old World monkeys and apes, which all have good vision, including color. Having evolved for one purpose, a good eye for color, detail, and movement later became useful for other purposes, such as social interactions in groups.
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|Publication:||USA Today (Magazine)|
|Date:||Sep 1, 2006|
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