Comparative Analysis of Spatial Hearing of Terrestrial, Semiaquatic and Aquatic Mammals

Abstract

The comparative analysis of own experimental researches of accuracy and mechanisms of orientation in acoustic space of the Black Sea bottlenose dolphins, north fur seals and dogs were accomplished depending on parameters and environment of sound distribution. From all of the probed representatives of marine mammals dolphins differ the most exact indexes of sound source localization (1.5-2o). Fur seals localization possibilities in water are substantially less to such the dolphins in 1.6-1.8 time in a horizontal plane and in 5-9 times, sometimes more in a vertical plane. The accuracy of localization of sound source by fur seals in a horizontal plane in air (3.5-5.5o) a few exceeds such in water (6.7-7.5o) and appeared substantially better, than for dogs (7-11o), but in 1.5-2 times worse, than in water in a vertical plane . The mechanisms of acoustic orientation depend on the type of animal, his ecology, parameters, conducting path, sound path environment, features of sound path structures. For all speeches the direction of acoustic signal arrival encoding is carried out by means of space-frequency filtration and interaural differences. Peculiarities, accuracy and mechanisms of acoustic orientation of high level progress animals are investigated during many years by different authors using various methods. We have been already working on this theme over 30 years, in particular carrying out experimental researches (using behavioral response techniques operant conditioning with food reinforcement) of main characteristics of hearing, including space hearing, of aquatic and semiaquatic mammals – bottlenose dolphins and pinnipeds big-eared and real seals (northern sea fur-seal and Caspian seals). The results of our researches and survey of summary of other authors’ works are cited in our articles (Babushina, 1979, 1997, 1998, 1999, 2000, 2001 a, b, c; Babushina et al., 1991; Babushina & Polyakov, 2001, 2003, 2004; Babushina & Yurkevich, 1994 a, b; and others). All investigated mammals’ representatives showed excellent abilities to take their bearings in space by means of hearing: to discover successfully acoustic signals, with high enough accuracy (but for every species – with its own one) to determine the place of the sound source, to define operating factors of signals, delicate structure of composite sounds, to use all functional possibilities of acoustic analyzer for solution of complicated experimental problems. Perhaps, at first it was a success for us to carry out multi-aspect, complex researches of peculiarities and mechanisms of mammals’ acoustic orientation with different adaptive modifications of peripheral structures of hearing organ. It was determined, that main physical principles of sound source localization, using