Quality of Diet Decides Survival of Whales and Dolphins

The food consumed by whales and dolphins is what decides their survival.  High-energy prey make for high-energy predators in the marine world. The quality of diet plays a crucial role in conservation, according to a study.

This study was conducted by the researchers from the Universities of British Columbia and La Rochelle, in France.

"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."

In order to prove the hypothesis, the researchers compared the diets of 11 species of whales, dolphins and porpoises in the Northeast Atlantic Ocean. They noticed a remarkable difference in the qualities of prey consumed that could not be explained by the different body sizes of the predators. 

The aim at carefully noticing 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," said Trites. "The two have co-evolved."

According to Jerome Spitz, the study's first author, the research will help better assess the impact of resource changes on marine mammals.

"Species with high energy needs are more sensitive to depletion of their primary prey," said Spitz, a postdoctoral fellow at ULR in France, who completed the research while a visiting scholar at UBC. "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."

This study was published on Nov. 21 in the online journal PLOS ONE.