Many people see only a blur of variation when they look at a reptile or amphibian. But scientists have found that clusters of these creatures, adapted to specific ecological niches, are distinct. These are the species.
Despite their unique adaptations, most reptiles are at risk. Climate change threatens lizards in tropical biomes, and snakes in arid habitats.
In the wild, snakes spend 70% of their lives solitary and focus on tracking down, killing, and digesting their living prey. They have good eyesight and can taste air particles using their forked tongues, which they use to lick the air for moisture, odors, and other chemicals, a behavior called “tasting.”
Snakes are a unique group of reptiles, as they tend not to aggregate at denning sites or mating areas. There is a general tendency for some species to congregate in seawall caves at parturition time, but this may be a result of the availability of safe places for females to lay their eggs rather than an instinctive urge.
The bodies of all snakes are supported by a system of ribs that is flexible enough to accommodate their long lengths, and they breathe through lungs located in their slender bodies. Their skin is covered with rough horny layers of scales or bony plates, and it is composed of keratin, the same substance that makes up the hair, nails, and claws of mammals and birds. The scales are arranged in distinctive patterns, which are used for taxonomic purposes. They shed their skin regularly to maintain good health.
Most snakes are able to regulate their internal body temperature by the way they move and by adjusting the amount of light they receive. In addition, they can enter a special state of inactivity, or brumation, that allows them to survive extreme winter temperatures by storing energy and slowing their heart rate.
Lizards, which are a suborder of reptiles called Squamata, are a diverse group that range from the tiny geckos and skinks to the giant Komodo dragons. They are distinguished by a unique skull morphology, including one jaw bone that corresponds to the mammalian malleus and incus – this allows them to hear high-frequency sounds that mammals cannot.
They are a key part of the food chain in many ecosystems, helping to control rodent and insect populations and providing important ecological services, such as nutrient cycling. However, some reptiles are also of major concern to humans because they are venomous or present threats to human health, such as salmonella.
Most lizards have a closed circulatory system with a three-chamber heart, comprising two atria and one variably-partitioned ventricle. This system gives them more control over their blood flow, allowing them to shunt deoxygenated blood from the body to the lungs when needed.
Their ability to camouflage and remain still for long periods of time helps lizards avoid predators. But some lizards need to take more active measures to stay safe, such as the desert horned dragon, which can release a toxic smoke from its nostrils when threatened by an enemy. The tail of some lizards is also designed to break off, giving the lizard the chance to escape its enemies’ grasp.
Turtles, tortoises, and terrapins are placed in the order Testudines (Chelonia). This group is one of four groups of living reptiles. They all share certain key characteristics, such as a body covered in scales or scutes and laying shelled eggs. They also have lungs and are ectothermic, meaning that they depend on the environment to regulate their body temperature.
The Integrated Taxonomic Information System breaks the turtle species into two suborders: Pleurodira and Cryptodira. The distinction comes from how the turtles retract their heads into their shells. The clade of side-necked turtles, which pull their heads in sideways, is Pleurodira, while the clade of hidden-necked turtles, which draw their necks straight back into their shells, is Cryptodira. There are 363 species of turtles, found on every continent except Antarctica.
These omnivorous animals prey on aquatic plants, snakes, fish, frogs, worms, and other turtles. Male and female turtles mate with a mating ritual that varies by species. Some turtles fight for the right to mate, while others seduce their potential mates by intertwining their tails so that their openings in their shells line up perfectly.
The deterioration of wildlife habitats around the world is the greatest threat to turtles, which can be difficult to survive in disturbed areas. For example, off-road vehicles destroy desert tortoise habitat, and urban rain runoff can carry toxic chemicals into lakes, rivers, and streams where turtles live.
Crocodiles, also known as crocodylia, are semi-aquatic reptiles that live both in and out of water. They are found throughout the tropics in Africa, Asia, Oceania and North America. These powerful predators are renowned for their camouflage and ambush hunting skills, but also possess great speed and strength, particularly in the water. Their streamlined bodies and webbed feet reduce the amount of water resistance they create when swimming.
They are the most powerful carnivores in their natural environments and occupy the top of their food chains. They hunt by ambushing prey and dragging them underwater to drown. They use their strong, powerful jaws and teeth to eat fish, birds, mammals, frogs, crocodiles and other reptiles. They can even bite through bone.
There are 13 species of crocodiles, including both freshwater and saltwater varieties. They are very adaptable, living in both wet and dry climates, but favor wetlands. These animals are cold-blooded and can not generate their own body heat, so they depend on sunlight to keep warm. In addition, they can go into a state of deep sleep, or aestivation, to conserve energy.
The snouts of these creatures vary in length and shape from family to family, with some being narrower than others. Species are identified by the proportion of the snout and the number, shape and arrangement of the scales. They are also distinguished by the thick bony plates on their backs and by the presence of a small, short tooth on the end of their snouts, which they use to break open eggs.