Feeding Behaviour and Feeding Motorics in Subadult European Pond Turtles, Emys orbicularis (Linnaeus, 1758)

The European Pond Turtle is a predominantly aquatic species, generally assumed to feed exclusively under water by using hydrodynamic mechanisms. We analysed the kinematics of the aquatic food uptake and food transport by using high-speed videos with 500 fps. The analyses revealed that subadult E. orbicularis use compensatory suction for food uptake, but the food transport is performed by a combination of compensatory and inertial suction mechanisms. In contrast to other aquatic and semi-aquatic testudinoids studied to date, the static maximum gape phase (MG-phase) was not an obligatory element of the ingestion and transport gape cycles of the European Pond Turtle. Our results show that the aquatic food uptake kinematics were rather uniform, which might indicate a feed-forward controlled motor program. In food transport cycles, our experimental specimens showed individual kinematical variations. In the European Pond Turtles terrestrial feeding seemed to be challenging. Recently it was reported that the adults of this species are able to fulfill the whole feeding process including food uptake, food transport, pharyngeal packing and swallowing on land. We tested whether subadult European Pond Turtles can feed on land as well. During our investigation we did not detect any of the subadult European Pond Turtles to attempt terrestrial food transport. Very rarely the turtles grasped food offered on land by their jaws, but dragged it immediately under water for further manipulation and swallowing.