turtle

Turtle is a common name for reptiles in the order Testudines (also called Chelonia). Turtles are distinguished by a permanent shell that protects the body. The shell consists of a dorsal carapace and a ventral plastron, formed by plates of bone fused to the ribs and spine. The outer surface bears scutes made of keratin. Turtles are air-breathing vertebrates with a wide range of sizes and life histories and are found in a variety of habitats, from deserts to oceans.

Most turtles fall into three broad groups: sea turtles that spend most of their lives in saltwater, freshwater turtles that inhabit rivers, lakes, and swamps, and tortoises which are primarily terrestrial. The term turtle is used differently around the world; in some regions it refers specifically to aquatic species, while in others it encompasses all members of Testudines.

Diet varies by species and life stage. Some turtles are herbivores, feeding on aquatic vegetation, while others are omnivores or carnivores, consuming invertebrates, fish, or jellyfish. Reproduction involves laying eggs on land; females often return to nesting sites, where eggs are buried in the substrate. Incubation times and hatchling survival vary, and temperature can influence sex determination in many species.

Conservation status also varies. Numerous turtle species are threatened by habitat loss, pollution, hunting, and bycatch in fisheries. International treaties and national protections aim to reduce harvesting and protect critical habitats, while conservation programs work to protect nesting beaches, manage habitats, and support captive breeding and release efforts.