The Umwelt concept of Jakob von Uexküll considers animals as subjects that inhabit their own subjective universe which is determined by the animal's sensory perception and cognitive abilities. Dolphins present an interesting species to investigate its Umwelt because cetaceans underwent a drastic change in lifestyle in the course of evolution because these mammals returned from a terrestrial life back into the water. Although bottlenose dolphins are intensively studied there are still many knowledge gaps. Here we studied some aspects of the dolphins' Umwelt by asking: (1) how their nocturnal acoustic Umwelt is arranged; (2) what the production of vocal copies can tell us about the dolphins' perception of their environment; (3) whether they are able to perceive tastes (4) or odours; (5) whether they are sensitive to magnetic stimuli. We found that the dolphins' nocturnal Umwelt was characterized by a temporally patterned vocal activity that also included vocal copies of sounds that the dolphins had heard during the day. This is a striking separation between auditory memory formation and vocal copy production and the copies might be a vocally expressed nocturnal rehearsal of day events. Thus, vocalizations can serve as possible indicators of events or objects that are meaningful to the dolphins. Regarding dolphins' perceptive abilities, we found that they were sensitive to both gustatory and olfactory food-related stimuli. They might use this ability to locate and/or evaluate prey. Further, dolphins responded to a magnetic stimulus, suggesting that they are magnetosensitive, what could be useful for navigation. So far, chemo- and magnetoreception have not been considered seriously as potentially functional in dolphins. The results obtained during this thesis fill some of the gaps that still exist in the knowledge of the dolphin's Umwelt and therefore contribute to a better understanding of this species. Moreover, they illustrate that even already intensively studied species may still hold important facets of their biology to reveal and that research should broaden the view and remain unbiased when studying a topic.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-00987730 |
| Date | 11 December 2013 |
| Creators | Kremers, Dorothee |
| Publisher | Université Rennes 1, Université européenne de Bretagne |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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