The Antarctic minke whale (Balaenoptera bonaerensis) is a baleen whale species that inhabits the frigid waters of the Southern Ocean. As a member of the rorqual family, these whales filter their food using baleen plates instead of teeth. They represent a significant component of the Antarctic marine ecosystem, particularly as krill predators. Understanding this species offers insight into the broader health and dynamics of one of the planet’s most unique and remote environments.
Physical Characteristics and Identification
The Antarctic minke whale has a sleek, streamlined body. Adults reach lengths of 8.5 to 9.0 meters, with some growing up to 10.7 meters, and can weigh up to 14 tonnes. Females are slightly larger than males.
Their coloration is dark gray on the dorsal (upper) side and white on the ventral (underside), with grayish streaks or lobes on their sides. A distinguishing feature, unlike its Northern Hemisphere counterpart, is the lack of a white band on its flippers, which are solid gray with a white leading edge. Their head is pointed with a prominent median ridge, and they have two blowholes. A moderately tall, sickle-shaped dorsal fin is located about two-thirds down their back. They also possess 22 to 38 abdominal pleats along their throat.
Habitat and Behavior
Antarctic minke whales are found exclusively in the Southern Hemisphere, from 10°S latitude south to the ice edges of the Antarctic continent. During the austral summer, these whales congregate in large numbers in Antarctic waters, particularly near the ice edge and among pack ice, where food is abundant. Some individuals break several centimeters of ice with their pointed snouts to create breathing holes.
As winter approaches, many migrate north to warmer temperate or tropical waters for breeding, though some remain in the Antarctic throughout the year. They are typically found alone or in small groups of two or three individuals. Larger aggregations of 10 to 15, or even up to 60 whales, occur in high latitudes during specific feeding or social periods. These whales are known for their curiosity, sometimes approaching stationary boats, and they perform breaches.
Diet and Feeding
The diet of the Antarctic minke whale primarily consists of Antarctic krill (Euphausia superba), abundant in the cold Southern Ocean waters. They also consume ice krill (Euphausia crystallorophias) in coastal shelf areas like the Ross Sea and Prydz Bay. Other small crustaceans and fish, such as Antarctic silverfish, Antarctic lanternfish, and certain amphipods, also include their diet.
They employ a lunge-feeding strategy to capture their prey. This involves gulping large volumes of water containing krill and then using their 200 to 300 baleen plates to filter out the prey. The baleen acts like a strainer, allowing seawater to pass through while trapping the krill. These whales can consume 2.7% to 4.0% of their body weight in food daily, equaling 83.7 to 325.5 kg of prey. They feed at high rates, sometimes lunging up to 100 times per hour under the sea ice, where krill aggregate.
Conservation Status
The Antarctic minke whale is currently listed as “Near Threatened” by the IUCN Red List, while other organizations classify them as “Least Concern” or “Not At Risk.” Historically, after larger whale species were overhunted, minke whales became a primary target for commercial whaling fleets in the Southern Ocean by the early 1970s, continuing until a general moratorium began in 1986. Although Japan ceased whaling in the Antarctic in 2019, they previously conducted “scientific research” whaling that included Antarctic minke whales.
Current threats to the Antarctic minke whale population include entanglement in fishing gear. Climate change poses a risk as it impacts their primary food source, krill, and alters their sea ice habitat. The melting of the Antarctic ice sheet directly disrupts their feeding grounds. Other challenges include ship strikes and ocean noise pollution, which can interfere with their communication and navigation. International agreements and organizations are involved in monitoring and protecting these whales.