Abstract
Bio-logging technology has started from using mechanical Time Depth Recorder (TDR) to
measure simply dive depth and duration of marine mammals and birds. However recently it has
remarkably advanced as highly sophisticated animal borne observation system. Digital electronic
technology enabled us to develop highly sophisticated small data logger system by which we
could obtain integrated information on animal behavior, ecology, physiology and environment
from underwater, which are still invisible and inaccessible for us. Now we are able to add more
ocean observation sensors to the system such as optical sensors, and much more integrated in
formation on not only animals but also whole ocean phenomena will be obtained, which will
bring us new knowledge about ocean.
