Development of small size data logger to observe marine animals

By using a data loggers attached to a marine animal, it is possible to obtain information directly about behavior and physiology of the animal. Here, the authors describe these data loggers. Because the data logger must not hinder the animal, it should be as small and lightweight as possible. Depending on the sensors that are built-in, the data logger is capable of recording the following variables: (a) environmental temperature and the animal's body temperature; (b) the water depth; (c) swimming speed; (d) illuminance; (e) acceleration; (f) terrestrial magnetism; (g) EKG; and (h) image. The authors successfully obtained data on swimming depth, water temperature, core body temperature, swim velocity, heart rate and other processes from marine mammals, diving birds, reptiles and fishes.