Introduction to Reptiles

Physical features

• Reptiles are ectothermic, meaning they regulate their body temperature using external sources. For example, they might burrow underground in hot environments or bask in sunlight in cool environments. Some species enter a state of torpor or brumation if their environment will be cold for an extended time.

• Their skin is covered in either scales or scutes, which keep their bodies from drying out, even in dry environments. Their scales are not separate structures (like fish scales), but instead are connected in a "sheet" which is the outermost layer of skin. This layer of skin is occasionally shed and replaced as the individual grows. In some species, it flakes off in chunks. In snakes, and some lizards, it is usually shed in one piece.

  • • When snakes shed their skin, it will usually come off in one piece. Shedding starts at one end of the body as the skin pulls away from the skin, like we might take off a sock. An individual will scrape against objects like branches and rocks to begin peeling off the dry skin and once it comes loose, the snake essentially just slithers out of the old skin. What's left behind is inside-out.

Diet

• Wild – All snakes and crocodilians are strictly carnivores. Most lizards are insectivores. Most turtles are omnivores, although the majority of tortoises are strict vegetarians.

• Zoo – Carnivorous species are fed mice, chicks, or rabbits that have been humanely euthanized, frozen for at least 72 hours, then thawed. Insectivores are fed a variety of live, and in some cases freeze-dried, insects and other invertebrates (crickets, roaches, fruit flies, mealworms, superworms, etc.). Herbivorous species are fed salads comprised of mixed greens (e.g., kale, collard greens, romaine lettuce) and fresh produce (squashes, sweet potatoes, carrots, seasonal fruits, etc.). Dietary items may be dusted with supplemental calcium or other vitamins depending on the species or individual's needs. Most species are not fed every day. Feeding schedules are dependent on the size of the animal, the season (i.e., their energy needs), the size of their previous meal, and the natural history of the species. Some species may go a month or longer between feedings.

Reproduction

• Most reptiles make nests or dig holes to lay eggs, but about 20% of Squamata species (snakes and lizards) bear live young.

• Some species (alligators, crocodiles, some tortoises, and some snakes) stay to guard the nest, but most reptiles leave the nest once the eggs are laid.

• Hatchlings are independent from the start and must find their own food. However, in many reptile species, the young may stay with or near one or more of their parents for a period of days to months, or even years in some species.

• Reproductive ages vary between groups and species.

  • • Crocodilians reach maturity between 4-15 years of age.

    • Most snakes reach maturity between 1-3 years of age.

    • Lizards reach maturity between 18 months to 7 years of age, depending on the species.

    • Testudines reach maturity between 5-25 years of age.

Interpretive Information

• There are more than 10,000 known species of reptiles.

• The heaviest reptile is the saltwater crocodile, which can weigh up to 2,000 pounds.

• The smallest reptile is the so-called "nano chameleon," Brookesia nana, from Madagascar with a body length of only about half an inch. This species was recently described in 2021.

• The longest snake is the reticulated python, but the heaviest is the green anaconda.

• The largest lizard is the Komodo dragon, though the crocodile monitor of New Guinea is considered the longest.

• The largest and heaviest Testudine is the leatherback sea turtle, reaching up to 8 feet in length and weighing up to 1,800 pounds.

• Crocodilians and snakes grow throughout their entire lives, a condition known as "indeterminate growth." However, while they continue to grow, they slow down considerably as they age, which is why we don't see 100 foot long snakes.

• Many reptiles can go long stretches of time (months or even years) without eating. Crocodilians and many lizards can do this thanks to extra fat stored in their tails. Reptiles also conserve energy (burn fewer calories) to keep warm, since their environment usually keeps them at the right temperature. For this reason, they don't need to consume as much as similarly-sized endothermic animals, like mammals, for their bodies to operate.

• Snakes and lizards lack eyelids and have a clear scale (called a spectacle) that covers and protects the eye from damage. This can make it difficult to tell when they are sleeping.

• Many lizards and snakes rely on their sense of smell to locate food and/or mates. They use their tongue to catch scent particles which are processed by the vomeronasal organ (also known as Jacobson's organ).

Updated August 2022