Inertial navigation as a basis for animal navigation

Abstract

The phenomenon of animal navigation has thus far not been completely explained in physiological terms, although it now appears to be well established that several species utilize celestial aids in their navigation. The remarkably successful development in recent years of self-contained Inertial Navigation Systems for automatic indication of position and for the control of motion of man-made vehicles (missiles, airplanes, submarines) suggests the necessity of a reconsideration of some aspects of the problem of animal navigation in the light of these developments. The basic principle of inertial navigation is that of determination of direction, and of distance travelled, by means of a double integration with respect to time of acceleration, due regard being made for the fact that the motion is carried out with respect to a spherical, rotating earth. Certain inertial systems of a hybrid type utilize celestial navigation as a supplementary aid; for this purpose automatic star-tracking devices are employed. From a close examination of published experimental results it cannot be said that an explanation on an inertial basis of animal navigation is in accord with all of the available experimental evidence obtained from animals, but a number of experimental results that have previously appeared to be puzzling are found to be consistent with the possible existence of a physiological inertial system of either a pure or hybrid form. Accordingly, further investigation of the problems of animal navigation from the standpoint of inertial navigation, a possibility that has in effect long been considered, appears merited. Some additional specific experimental tests, including ones in orbiting earth satellites, are proposed. At least, from the principles of inertial navigation, a full definition and possible explanation in physiological terms of the often-used but ill-defined term, “sense of direction”, and of its logical complement, “sense of distance”, can be advanced. These two senses, which are complementary and interrelated, may be considered as integrated ones, based on a primary “sense of inertia”, for which the specific sensory receptors in vertebrates are the vestibular organs.