Krill Feeding Study Reveals How Blue Whales Become So Big
A new study found that the reason behind how blue whales maintain their big sizes can be explained by an efficient krill feeding strategy. The key is to conserve their oxygen reserves and overall energy from previous feeding episodes.
The manner with which animals are able to balance their energy gain and loss remains to be a challenging point of study for ecology experts. Large animals, particularly whales have long been believed to feed on abundant tiny krills during the entire day, no matter how the preys are grouped in the waters. However, in a new study by a team of researchers from the National Oceanic and Atmospheric Administration (NOAA) Fisheries, Oregon State University and Stanford University, a sophisticated approach to krill feeding by the whales was discovered.
The authors used digital acoustic recording archival tags (DTAGs) to see how blue whales behave and make their decisions while feeding on their preys. To perform their investigations, the researchers compared the foraging patterns of 14 tagged and 41 formerly tagged blue whales off a California coast. By combining the data from both groups that measured the density of krill (the animals' only prey) in the ocean, the researchers were able to come up with an analysis.
The findings of the study, published in the journal Science Advances on Friday, Oct. 2, showed that when the one-inch krills were widespread in the water or are less dense, the blue whales would pass up on frequently feeding on it so as to conserve energy for later use. However, when the density of the krill increased, the blue whales were found to "lunge-feed," or consume more prey and obtain energy per dive.
"Blue whales don't live in a world of excess," said Ari Friedlaender, study co-author and a principal investigator with the Marine Mammal Institute at Oregon State University's Hatfield Marine Science Center. He added that the choices that these species make are vital to their survival.
Friedlaender also compared the findings to when a person puts a hand inside two packs of pretzels, of which one is full and the other has fewer contents. More pretzels may be grabbed from the full bag in one go, compared to the less loaded bag
The researchers were also able to quantify the krill threshold of the blue whales. According to Elliott Hazen from NOAA Fisheries and co-author of the study, blue whales go on with their foraging activities at higher rates if there are approximately 100-200 krills per cubic meter. If the number is less than that, the blue whales opt to conserve energy and save it for later.
The findings of this study have given a new insight into the feeding specializations of the enormous blue whales. The newly-discovered information may pave the way for better protective measures for these species, which the International Union for Conservation of Nature considers endangered.
Photo: Oregon State University | Flickr