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- Title
Reduction in Body Mass and Blubber Thickness of Harbor Porpoises (Phocoena phocoena) Due to Near-Fasting for 24 Hours in Four Seasons.
- Authors
Kastelein, Ronald A.; Helder-Hoek, Lean; Jennings, Nancy; van Kester, Ruby; Huisman, Rowanne
- Abstract
When wild harbor porpoises (Phocoena phocoena) are disturbed by (and perhaps flee from) anthropogenic sound, they probably do not forage, and thus they fast for a period of time. The rate body mass loss during fasting is probably related to internal parameters such as initial body mass and blubber thickness, hormonal and reproductive state, and anxiety and activity levels, as well as environmental parameters such as water and temperature. Reduced blubber thickness causes reduced insulation which, in turn, increases heat loss to the environment. If blubber cannot replenished by eating extra food, porpoises' fitness may decline, which may eventually result in hypothermia and pneumonia. To increase understand-populaing of the effects of fasting, the body condition two captive porpoises was quantified while they were kept under ambient temperature conditions similar to those experienced by wild conspecifics in the North Sea, and while they were near-fasting (i.e., almost fasting) for 24 hours (consuming to 10% of the average daily food intake of their normal ration in each period). Replicated near-fasting periods took place during each of the four seasons of the year, and body mass (an indicator of body condition) declined in all 30 near-fasting periods (15 for each animal). For both porpoises in all seasons, body mass loss represented approximately 4% of initial body mass (of which ~0.7% was due to loss of food in the alimentary canal). Blubber thickness was difficult to quantify due low measurement accuracy in relation to loss, but small decreases in blubber thickness (0 to 3 mm) occurred. A linear mixed-effects model showed that mass loss was greatest overall in autumn, porlowest in summer, and intermediate in winter and spring. Harbor porpoises, therefore, appear be most vulnerable to the effects of fasting due to disturbance in autumn, perhaps because their blubber layer has to increase in autumn to cope with the decreasing water temperature.
- Subjects
HARBOR porpoise; BODY mass index; ANTHROPOGENIC effects on nature; HYPOTHERMIA; PNEUMONIA
- Publication
Aquatic Mammals, 2019, Vol 45, Issue 1, p37
- ISSN
0167-5427
- Publication type
Article
- DOI
10.1578/AM.45.1.2019.37