About Reptiles

What is a reptile?

Historically, there were four recognized orders within the class Reptilia: order Testudines (turtles and tortoises), order Squamata (amphisbaenians, lizards and snakes), order Crocodylia (crocodiles, alligators and gharials) and order Rhynchocephalia (tuataras; unique to New Zealand). However, we now know that birds (order Aves) are closely related to dinosaurs and crocodilians, and that crocodilians are more closely related to birds than they are to snakes, lizards and turtles. This means that order Aves is actually nestled deep within the historic class Reptilia, and that based on taxonomic orthodoxy birds are, in fact, reptiles. Despite this, most people continue to use the word “reptile” to refer to what we historically classed as reptiles (turtles, amphisbaenians, snakes, lizards, crocodilians and tuatara), and the Canadian Herpetological Society also uses the name in this historic context.

Like mammals, birds, amphibians and fish, reptiles are vertebrates (animals with a spinal column). Reptiles have dry, non-permeable skin covered in scales or bony plates. Although some reptiles live in aquatic environments (e.g. turtles, sea snakes), they all breathe air through lungs. Reptiles are ectothermic (commonly referred to as cold-blooded), meaning they do not generate their own body heat, but rather, their internal body temperature depends on the surrounding environment. Like birds, reptiles have amniotic eggs, which have a protective membrane, yolk and outer shell. However, some species of snakes and lizards do not lay eggs, but instead the female retains the amniotic egg (embryo and a basic placenta) during development and gives birth to live young.

Reptile diversity in Canada

As of July 2018, there are 10,793 known species of reptiles: 6,512 lizards, 3,709 snakes, 351 turtles, 196 amphisbaenians, 24 crocodilians, and 1 tuatara species (The Reptile Database 2018), and new species are discovered each year. Despite its northern latitude and cool climate, Canada has a reasonably high diversity of reptiles, with 10 extant turtle species (excluding some of the transient Sea Turtles), 33 extant snake species and 5 extant lizard species. Some species, such as the Common Gartersnake, are further broken into multiple subspecies across Canada, which are not reflected in these numbers.

Ecology and behaviour

Since reptiles are ectothermic, they regulate their body temperature through behaviour, such as basking in the sun to warm up or seeking shelter in the shade to cool down. Therefore, reptile behaviour and activity is largely dictated by environmental conditions. Metabolic activity and energy levels are dependent on temperature; reptiles are relatively slow and inactive when they are cold and are most active when they are warm. Reptiles have an optimal body temperature at which they are able to function most efficiently, and they have to maintain sufficient body temperature to digest their food, incubate young, and forage for food or escape from predators. In Canada’s cooler climate, having to spend long periods basking to maintain high body temperature can limit how much time reptiles have for other behaviours, such as foraging and mating. However, since they do not expend metabolic energy to maintain their body temperature, reptiles have much lower energy requirements than mammals or birds of similar size, and can go long periods of time without eating (sometimes months, in the case of large snakes).

Canada’s snakes and lizards avoid freezing temperatures during the winter by hibernating underground below the frost line (in mammal burrows, tree root hollows, rock crevices or other cavities), while turtles hibernate at the bottom of rivers, lakes or wetlands, beneath the ice. Since their body temperature drops to that of the surrounding environment, which may be as low as 1-2°C in the hibernation site, metabolic rate slows dramatically, allowing reptiles to survive for months with no food and very little oxygen. Turtles are able to obtain what little oxygen they require from the water by absorbing it through the lining of their mouth and cloaca. During the active season (e.g. when they are not hibernating), reptiles are most active during warm weather, when they can easily maintain optimal body temperatures.

Where do they live?

Reptiles are adapted to living in a wide diversity of habitats, from cold northern climates to deserts and everything in between, as well as freshwater environments and oceans (polar regions excluded). Despite the diversity of habitats they occupy, all reptiles require access to areas that receive direct sunlight or are sufficiently warm enough to maintain an appropriate body temperature. All extant turtle species in Canada are aquatic, living in freshwater ponds, lakes, rivers and wetlands, and the ocean, in the case of sea turtles that frequent Canadian coasts. Although they spend most of their time in water, turtles use terrestrial habitats for nesting or moving between aquatic habitats. Some freshwater species, such as the Wood Turtle, may spend the majority of the active season on land. The Eastern Box Turtle, which was historically found in southern Ontario but is now extirpated from Canada, is entirely terrestrial and lives in woodlands. Most snakes and lizards are terrestrial and inhabit a wide variety of environments ranging from forests to grassland to deserts. However, some snake species, such as the Queensnake and Common Watersnake, are semi-aquatic and forage primarily in lakes, rivers and wetlands.

Reproduction

All reptiles in Canada have internal fertilization, meaning that males and females must copulate for fertilization to occur. Mating occurs during the active season, with the specific timing (e.g., spring or summer) varying between species. Reptile eggs are more resistant to drying out than amphibian eggs and can be laid on land, which has allowed reptiles to colonize and thrive in dry environments far from water. However, most reptile eggs will drown if submerged under water for extended periods of time. Female turtles lay their eggs on land in nest cavities that they excavate in sand, gravel or other soft substrates, typically close to the water. Sea turtles, which inhabit Canadian waters for parts of the year, migrate south to nest on beaches in tropical regions. Snakes and lizards lay their eggs in sites that are protected from predators and the elements, such as under rocks, logs or vegetation, in rotting logs or underground in animal burrows. Female hog-nosed snakes, however, also use their upturned snout to excavate nest sites in sandy habitats. Females of live-bearing snakes and lizards are able to protect the developing young inside their body and ensure optimal temperature and humidity for development. This strategy helps these species survive in colder climates, since females can reduce the incubation time of their eggs by basking.

Most species of snakes do not demonstrate parental care, leaving the eggs or young to fend for themselves; female rattlesnakes, however, remain with their young for a few days to a week after birth, protecting them from potential predators. Some female lizards display parental care and remain with their eggs until they hatch in late summer, protecting them from predators and turning the eggs to ensure optimal moisture levels.

What do they eat?

Most turtles in Canada are omnivorous, feeding on vegetation as well as a variety of animal prey, such as invertebrates, fish, frogs, and carrion. However, some turtles have very specialized diets, such as Northern Map Turtles, which use strong jaws to crush and eat mussels and snails, and Leatherback Sea Turtles, which follow warm currents into Canadian waters to forage for jellyfish. Most of Canada’s turtles feed in the water, where the flow of water into the mouth helps draw food inwards. Lizards feed on a variety of invertebrates, such as insects, spiders and earthworms, which they actively hunt with their keen senses of sight and smell. Some lizard species have specialized diets, such as the short-horned Lizards, which feed primarily on ants. All snakes are carnivorous, although the type of prey and how it is captured varies. Canada’s snake species prey on a wide range of animals, including insects, slugs, worms, fish, frogs, toads, salamanders, small mammals, birds and their eggs, and other snakes. Some species consume a range or prey, while others are specialists and have a much narrower diet preference. For example, the Common Gartersnake will eat almost anything it can swallow, while the Queensnake is a specialist, feeding entirely on freshly-moulted crayfish. Most snake species in Canada actively search for their prey, although some species, such as the rattlesnakes, employ a ‘sit and wait’ tactic. Some snake species consume their prey alive (e.g., gartersnakes and watersnakes), while others employ venom (e.g., rattlesnakes) or constriction (e.g., rubber boas and ratsnakes) to kill prey before swallowing it. Snakes have highly elastic ligaments between their jaw bones, enabling the mouth to stretch open wide enough to swallow prey that is much larger than their head.