Physiological and behavioral thermoregulation in bottlenose dolphins (Tursiops truncatus) in Sarasota, Florida
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Michelle Marie Barbieri (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Ann Pabst
Abstract: The temperature differential (?T) between a body surface and the ambient
environment is one factor that influences heat loss. Organisms can affect ?T
physiologically, by controlling body surface temperature, and behaviorally, by choosing
the ambient temperature to which they are exposed. These physiological and behavioral
mechanisms of thermoregulation were investigated across seasons in a resident
community of bottlenose dolphins (Tursiops truncatus) in the Sarasota Bay, Florida
region, where water temperatures range annually from 11 to 33oC. Because the dorsal fin
is a highly dynamic thermal window, temperatures of this surface were measured on
wild, free-swimming dolphins using infrared thermography. Distribution of these yearround
resident dolphins was compared across seasons to assess whether or not local
changes in distribution reflect seasonal use of microclimates. Independent, continuous
measurements of water temperature at eight locations throughout the region were used to
describe the annual thermal profile of Sarasota Bay.
To calculate ?T, water temperatures measured during thermal imaging were
subtracted from dorsal fin surface temperatures. There was a positive, linear relationship
between dorsal fin surface temperature and water temperature, as mean ?T across all
seasons was similar. Dorsal fin surface temperatures appear to be modulated in response
to environmental temperature to maintain a steady ?T at the dorsal fin skin surface across
seasons. In winter, increases in insulation, both integumentary (i.e. blubber) and vascular
(via reduced perfusion and utilization of countercurrent heat exchangers) must account
for the protection of core temperature and stability of ?T. Water temperature throughout the Sarasota Bay region changed dramatically
across seasons and, overall, these patterns were similar throughout the study area.
Temperatures tended to plateau in both winter and summer, and change continuously in
spring and fall. Overlaid on this annual pattern of temperature change were short-term,
cyclical variations in water temperature, with peak frequencies at 11 and 19 days. The
amplitudes of these cyclical changes could vary between sites, creating regional
heterogeneity in water temperatures across the study area. The amplitudes of these
cyclical changes were more pronounced in winter than in summer at all sites; thus,
temperatures within the summer were the most stable of any season.
To assess dolphin distribution, individuals were classified based on age, sex and
reproductive status. Within a season, distribution patterns appeared to be specific to
particular dolphin classes. Though not always significant, differences between these
distribution patterns were more apparent in summer, spring, and fall, and less so in
winter. Water temperatures during summer were, overall, the least variable, and in the
transitional spring and fall seasons, water temperatures across the seven measurement
sites were most similar to each other. In contrast, during winter, when water temperature
oscillations could vary by up to 6°C over a period of 10-11 days, dolphin classes were
more similar in their distributions.
The relationship between dolphin distribution and water temperature was
investigated to assess whether or not a particular dolphin class was consistently observed
in warmer or cooler water temperatures, relative to any other dolphin class. In only one
dolphin class, and in only one season, was there a significant statistical relationship.
Adult males in summer were found to be distributed in significantly cooler water temperatures than all other classes. This result is interesting, as adult males have the
smallest surface area to volume ratios across which heat dissipation may occur, in
comparison to other dolphins, and it was found in summer, when water temperatures are
warmest and most stable. Thus, water temperature may be an important factor
influencing the distribution of adult male dolphins, but other biotic and abiotic factors
likely play an important role in dolphin distribution throughout the Sarasota Bay region.
Physiological and behavioral thermoregulation in bottlenose dolphins (Tursiops truncatus) in Sarasota, Florida
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Created on 1/1/2009
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
- Language: English
- Date: 2009
- Keywords
- Bottlenose dolphin--Behavior, Body temperature--Regulations, Bottlenose dolphin--Physiology
- Subjects
- Bottlenose dolphin -- Behavior
- Body temperature -- Regulations
- Bottlenose dolphin -- Physiology