Semi-aquatic turtles – biology

Semi-aquatic turtles can be also called pond turtles. I think that these names can be used interchangeably in this case, because they both reflect the characteristics of their lifestyle and environment. This also seems correct because the name “aquatic turtles” seems best reserved for those species that do not use the land for sunbathing or searching for food. Only females leave the water for the time of laying eggs – just like sea turtles.

They won’t survive without water

Pond turtles love sunbathing. This allows them to absorb thermal radiation, which is necessary to raise their body’s temperature, get energy for active food search and regulate metabolic processes. They can also move smoothly on land and they do it for reproduction, seeking new habitats and food. However, they are so strongly connected with the aquatic environment that staying outside for too long leads to dehydration.

Senses of semi-aquatic turtles

Without any doubt, pond turtles have extremely well developed senses of sight, smell and hearing. This is essential for locating food, avoiding predators and also important in finding the right partners during the breeding season. All freshwater turtles have a thin, transparent third eyelids that cover their eyes when submerged, to enable them to see effectively underwater. The smell, on the other hand, is highly developed thanks to the vomeronasal organ (or Jacobsen organ), which is located in the turtle palate. Its task is to detect and identify fine fragrance particles floating in the air and water. Turtles do not have an outer ear, instead they have a tympanic membrane (eardrum). The inner ear is surrounded by a bone structure. Turtles hear low frequency sounds best, both  water and to a lesser extent on land.

Systematics

Semi-aquatic turtles are mainly species grouped in the Emydidae family, which also includes our native pond turtle, Emys orbicularis. This family includes the following types;

    Chrysemys

    Clemmys

    Deirochelys

    Emys

    Glyptemys

    Graptemys

    Malaclemys

    Pseudemys

    Terrapene

    Trachemys

Semi-aquatic turtles also include representatives of Geomedidae and probably the most popular and easily available domestic Chinese pond turtle – Mauremys reevesii.

Dawid Krótki