Researchers from the University of British Columbia and University of La Rochelle, in France found that marine predators' survival hinges on the quality of their diets and this plays an important role in conservation.
"The conventional wisdom is that marine mammals can eat anything," said co-author Andrew Trites, a marine mammal expert at UBC.
"However, we found that some species of whales and dolphins require calorie rich diets to survive while others are built to live off low quality prey - and it has nothing to do with how big they are," Trites said in a statement.
The team compared the diets of 11 species of whales, dolphins and porpoises in the Northeast Atlantic Ocean, and found differences in the qualities of prey consumed that could not be explained by the different body sizes of the predators.
The key to understanding the differences in their diets was to look at their muscle performance.
"High energy prey tend to be more mobile, and require their predators to spend more energy to catch them. The two have co-evolved," Trites said.
Jerome Spitz, the study's first author, said the research will help better assess the impact of resource changes to marine mammals.
"Species with high energy needs are more sensitive to depletion of their primary prey," said Spitz.
"It is no longer a question of how much food do whales and dolphins need, but whether they are able to get the right kinds of food to survive," Spitz added.
The study was published in the journal PLOS ONE.
