All three
animals come under the class of reptiles, in the taxonomic order of
Testudines or Chelonia. They all have the major characteristics of
reptiles as they are cold-blooded, have scales, breathe air, and lay
eggs on land.
The distinction between them comes mainly from what living habitat
they are adapted for, though the terminology differs slightly in
certain countries. In Australia, other than marine sea turtles, they
are all called tortoises. In the United States, the term ‘turtles’
is given to chelonians that live in or near water.
In general there are a few commonly accepted distinctions between
turtles, tortoises, and terrapins. Turtles may be completely
aquatic, like sea turtles, which rarely come up onto land, except to
lay eggs. Other types of turtles are semi-aquatic and live by fresh
water ponds or lakes. They tend to swim, but also spend a lot of
time on land, basking in the sun and occasionally burrowing in the
mud. Turtles have adapted to an aquatic life and are streamlined for
swimming with webbed feet, or in the case of sea turtles, long
flippers. Turtle are omnivores. Depending on the type of turtle,
they may eat jelly-fish, small invertebrates, sea sponges, and other
sea-vegetation. In the case of fresh water turtles, they may eat
plants, insects, and small fish.
Tortoises are almost exclusively land-dwelling, usually with stubby
feet, and are not good swimmers. They occasionally enter water to
clean themselves off or drink water, but can easily drown in the
deep or in strong currents. Their bodies are adapted to living on
land and have high domed shells and column shaped feet much like
elephants. They also sometimes have sharp claws for digging .
Tortoises are mostly herbivorous and primarily eat low-lying shrubs,
cacti, grasses, weeds, fruit, and other vegetation.
The term terrapins is sometimes used for turtles that are
semi-aquatic and live near brackish waters or swampy regions. They
are sort of like a mix between a turtle and tortoise, as they spend
most of their time divided between water and land. They are also
usually small and have a hard-shell that is shaped somewhere between
a turtle’s streamlined one and a tortoise’s rounded dome shaped one.