Minke Whales Can’t Get Any More Mini If They Want to Get Enough Food to Survive, According to A New Study.
A recent scientific investigation of Antarctic minke whales has uncovered crucial information regarding the minimum size requirements for whales that use the lunge-feeding technique. This feeding strategy, famously utilized by the blue whale, is highly efficient and has contributed to its status as the largest animal on the planet.
Lunge-feeding whales utilize an impressive technique whereby they rapidly accelerate towards a patch of prey, engulf a vast amount of water, and then expel the prey by filtering it through the baleen plates in their mouths. This feeding strategy is primarily employed by the rorqual group of baleen whales, which includes notable species such as blue, fin, humpback, and minke whales.
The key to the success of the feeding strategy of whales lies in their remarkable ability to swallow vast quantities of water filled with prey. This ability becomes more efficient as their body size increases, allowing them to maximize their energy intake. For instance, the massive 80-ton blue whale can engulf a staggering volume of water, which is equivalent to 135% of its body mass. In contrast, a smaller 5-ton minke whale can swallow a volume of water that equals only 42% of its body mass. This disparity highlights the advantage that larger whales have over their smaller counterparts when it comes to feeding efficiency.
A new study, published today in the scientific journal Nature Ecology & Evolution, has revealed important insights into the foraging behavior of Antarctic minke whales. Researchers utilized non-invasive suction tags to monitor a group of 23 whales as they fed on Antarctic krill in the waters off the West Antarctic Peninsula.
The study tracked the whales’ daytime and nighttime feeding patterns, providing valuable information on their behavior. To facilitate analysis, the researchers drew comparisons with data from previous studies of humpback and blue whales, both of which are also known to feed on krill.
“When we calculate how much energy they use in foraging and what their overall intake should be based on their size, we find that minke whales are right at the threshold,” says first author David Cade, adding, “anything smaller than a minke could not achieve the foraging rates necessary to survive.”
Minke whales aren’t studied as much as other baleen whales because they are harder to find and tag.
“The data in this study represent more information on a poorly studied species than has ever been published previously and is helping us to better understand not only the species, but the role of baleen whales in marine ecosystems,” adds coauthor Ari Friedlaender. “With so little known about this species that is being impacted by climate change, the more we understand their ecology and behavior the better we can protect them.”
The study found that minke whales exhibit a significantly high feeding rate, particularly during nighttime. The whales were observed lunging at an interval of approximately 15 seconds. This behavior can be attributed to the fact that krill, a primary food source for minke whales, rises to the surface during the night and stays in deeper waters during the day. As a result, these marine mammals have to dive deeper during the day, which is a less efficient feeding strategy for smaller animals.
“During the day they feed at depths comparable to humpbacks and blue whales, but their foraging rates aren’t as high because they’re smaller,” Cade adds. “Their nighttime feeding rates are two to five times the day rate.”
In the darkness of the night, the minke whales, which are smaller and more agile compared to other whale species, are ideally adapted for tracking and catching small, dispersed clusters of krill near the water’s surface.
“When they’re surface feeding, they don’t have to hold their breath during dives and they can do lunges over and over again,” Cade adds. “Only at night can they get the really high feeding rates they need.”
The research also discusses the origins of a feeding strategy that relies on huge body size as well as problems about the development of baleen whales. It is believed that whales the size of the present-day Antarctic minke whales were the first to develop lunge feeding. This made it possible for whales with huge bodies, like blue whales, to evolve over the past 5 million years, when changing ocean conditions led to the formation of predictable areas with large patches of prey that lunge-feeding whales could use to their advantage.
“Minke whales represent one extreme, at the small end of the spectrum, for how filter feeding in ocean predators evolved,” Friedlaender adds. “Understanding both the maximum and minimum size constraints on baleen whale size really helps us understand how this group of animals has evolved and how they affect and are impacted by marine ecosystems.”
Image Credit: Paul Souders via Getty Images