Reprints of the following papers are available upon request.
Also, comments or questions about the content of these papers are
welcome. You could even post comments here - seems like a while since
there has been a discussion on this list that was scientific
rather than equipment-related.
Mercado, E., III, Herman, L. M., & Pack, A. A. (2005). Song copying by
humpback whales: Themes and variations. Animal Cognition, 8, 93-102.
Male humpback whales (Megaptera novaeangliae) produce long, structured
sequences of sound underwater, commonly called "songs." Humpbacks
progressively modify their songs over time in ways that suggest that
individuals are copying song elements that they hear being used by other
singers. Little is known about the factors that determine how whales
learn from their auditory experiences. Song learning in birds is better
understood and appears to be constrained by stable core attributes such
as species-specific sound repertoires and song syntax. To clarify
whether similar constraints exist for song learning by humpbacks, we
analyzed changes over 14 years in the sounds used by humpback whales
singing in Hawaiian waters. We found that although the properties of
individual sounds within songs are quite variable over time, the overall
distribution of certain acoustic features within the repertoire appears
to be stable. In particular, our findings suggest that species-specific
constraints on temporal features of song sounds determine song form,
whereas spectral variability allows whales to flexibly adapt song elements.
Branstetter, B.K. & Mercado, E., III (2006). Sound localization by
cetaceans. International Journal of Comparative Psychology, 19, 26-61.
Cetaceans (whales and dolphins) use acoustic cues to determine the
locations and identities of environmental stimuli within their
underwater habitats. Dolphins evolved unique auditory systems for
spatially differentiating ultrasonic signals, whereas the larger baleen
whales appear to have evolved different mechanisms for localizing lower
frequency sound sources. Many of the cues that terrestrial mammals use
to localize sounds in air are less well suited for localizing sounds
underwater. Nevertheless, cetaceans can localize sounds as well as or
better than most terrestrial mammals. Position-dependent spectral
filtering likely plays an important role in sound localization by
toothed whales, whereas phase differences between the ears may be
important for baleen whales. However, it is exceedingly difficult to
determine how filtering and phase differences contribute to spatial
hearing by whales and dolphins because, in contrast to terrestrial
mammals, the structures through which cetaceans receive sounds are
completely internalized (and thus invisible). Computational models of
cetacean auditory processing provide one viable approach to generating
testable predictions about the mechanisms cetaceans use to localize and
identify sound sources.
|