269
chapter twelve
Visual and hydrodynamic flow perception
Frederike D. Hanke and Guido Dehnhardt
12.1 The big picture challenge
Marine mammals are generally very mobile species. Whereas some species undertake
large-scale movements, most marine mammals move on small scales within, for example, a home range. These movements are required for successful foraging or breeding.
Consequently, marine mammals regularly experience sometimes even tremendous
changes in the environment, and these changes occur when moving horizontally but also
vertically during dives. However, under all conditions, the animals have to rely on their
senses as interfaces between environment and behavior. While they generally assist orientation, the senses help to collect important information about general features of the
environment, predators, prey, or mating partners. Although an individual’s senses most
likely interact to form a multimodal representation of the environment (Dehnhardt 2002),
it may happen under certain conditions that only a few or, in the most extreme case, only
one sensory system is providing reliable information.
Among the senses, vision is of paramount importance from a human perspective. In
contrast, in marine mammals, the role of the visual system for underwater orientation is
controversially discussed. Many authors have speculated that vision cannot play a major
role underwater due to low light levels that seem to dominate the visual environment of
marine mammals. Low light levels are encountered at night but also when diving to deep
waters even during the day when marine mammals experience perfect light conditions
Contents
12.1 The big picture challenge ................................................................................................. 269
12.2 Knowledge by order .......................................................................................................... 276
12.2.1 The visual system: Adaptation to low light levels ............................................ 276
12.2.2 Basis for optic flow perception ............................................................................. 277
12.2.3 The vibrissal system: Adaptations to the aquatic medium ............................. 279
12.2.4 Basis for hydrodynamic flow perception ........................................................... 279
12.3 Toolbox ................................................................................................................................ 281
12.3.1 Operant conditioning ............................................................................................ 281
12.3.2 Psychophysics ......................................................................................................... 281
12.3.3 Particle image velocimetry ................................................................................... 283
12.3.4 Challenges associated with the investigation of senses underwater ............. 283
12.4 Unsolved mysteries ...........................................................................................................284
Glossary ........................................................................................................................................ 285
References ..................................................................................................................................... 287
chapter twelve
Visual and hydrodynamic flow perception
Frederike D. Hanke and Guido Dehnhardt
12.1 The big picture challenge
Marine mammals are generally very mobile species. Whereas some species undertake
large-scale movements, most marine mammals move on small scales within, for example, a home range. These movements are required for successful foraging or breeding.
Consequently, marine mammals regularly experience sometimes even tremendous
changes in the environment, and these changes occur when moving horizontally but also
vertically during dives. However, under all conditions, the animals have to rely on their
senses as interfaces between environment and behavior. While they generally assist orientation, the senses help to collect important information about general features of the
environment, predators, prey, or mating partners. Although an individual’s senses most
likely interact to form a multimodal representation of the environment (Dehnhardt 2002),
it may happen under certain conditions that only a few or, in the most extreme case, only
one sensory system is providing reliable information.
Among the senses, vision is of paramount importance from a human perspective. In
contrast, in marine mammals, the role of the visual system for underwater orientation is
controversially discussed. Many authors have speculated that vision cannot play a major
role underwater due to low light levels that seem to dominate the visual environment of
marine mammals. Low light levels are encountered at night but also when diving to deep
waters even during the day when marine mammals experience perfect light conditions
Contents
12.1 The big picture challenge ................................................................................................. 269
12.2 Knowledge by order .......................................................................................................... 276
12.2.1 The visual system: Adaptation to low light levels ............................................ 276
12.2.2 Basis for optic flow perception ............................................................................. 277
12.2.3 The vibrissal system: Adaptations to the aquatic medium ............................. 279
12.2.4 Basis for hydrodynamic flow perception ........................................................... 279
12.3 Toolbox ................................................................................................................................ 281
12.3.1 Operant conditioning ............................................................................................ 281
12.3.2 Psychophysics ......................................................................................................... 281
12.3.3 Particle image velocimetry ................................................................................... 283
12.3.4 Challenges associated with the investigation of senses underwater ............. 283
12.4 Unsolved mysteries ...........................................................................................................284
Glossary ........................................................................................................................................ 285
References ..................................................................................................................................... 287