Low fat or high fat diet
The study began in 2004 with four one-month-old newly weaned female harbor seals, the animals most susceptible to changes in prey availability. In 2005, the researchers added four more newly weaned one-month-old females to the study.
For marine mammals, most energy is provided by fat and protein, Polasek said. And fat is the easiest to convert to energy and blubber. Herring is one potential source of fat for harbor seals, she said. After weaning, pups must learn to effectively fish and accumulate sufficient fat stores for the winter, but changes observed in the distribution, composition or abundance of fish may make it harder to ingest and store enough fat. The study aimed to find out what effect the fat content of the harbor seals' diets has on their ability to survive and reproduce.
At the beginning of the study, the pups weighed between 21 and 33 kilograms (9.5 to 15 pounds). The researchers placed four of the seals in the high fat diet group and four in the low fat group. Both groups received an identical base diet, including pollock, squid, and capelin, all of which contain less than 4% fat. The remainder of the diet was herring.
The low fat group received herring that contained less than 6% lipids, while the high fat group received herring that was 16% lipids. (Herring have a higher fat content in winter before laying their eggs, but lose about one-third of their fat after releasing their eggs.)
Except for the fat content of the herring, the nutrient content was the same for both groups, Polasek explained. The researchers monitored the animals in the low fat group to ensure fat inta
Source:American Physiological Society