Why does my tortoise bite its shell

If a turtle falls on its back, its life is in danger. With her feet in the air, she is defenseless against enemies. Studies by Serbian researchers show that the largest specimens have the hardest straightening. Reptiles find themselves in such a predicament not only when children allow themselves a prank. Greek tortoises that live in the Balkans and Italy and grow to be 20 centimeters tall end up on their backs even when clumsy climbing in stony terrain, after fights with rivals - or when Ana Golubović arrives.

The biologist from the University of Belgrade and her team turned hundreds of turtles on their backs in order to study their strategies when erecting them. "Usually the animals try to hold on to a piece of plant or a stone and turn," she says. "In our experiments, however, they were lying on a flat piece of earth. They had to row hard with all extremities and rock back and forth until the claws found a hold in the earth." Of almost 500 animals, 58 percent of the females and 75 percent of the males managed this within ten minutes; then the researchers took pity. Successful reptiles took an average of three minutes.

For a further study, Golubović has now examined 118 particularly active turtles (Zoological indicator, online). The team was interested in what role the size and shape of the turtle played. It was found that a more domed shell helped the animals to straighten up, but that large turtles were more likely to have problems getting back on their feet. This particularly affects the females, which are larger than males in Greek tortoises. Nevertheless, growth is worthwhile because large females are more successful in breeding. Things are more complicated for males. Smaller animals are more mobile and are more likely to find a partner to mate. But larger ones are more likely to prevail in a fight with rivals - one strategy is to throw the other on their backs. In addition, larger males have a firmer stance during copulation, especially if they have slightly outward-facing horn plates on their hind legs. Golubović's results show that these prevent the animals from getting upright.