Balaenoptera bonaerensis is among the smallest rorqual species. Mature males average 8.36 m in length and weigh 6.85 tons, but they can reach a total length of 9.63 m and a weight of 11.05 tons. Females are slightly longer with a mean total length of 7.57 m and a maximum measured length of 10.22 m. On average, B. bonaerensis is slightly longer than all forms of B. acutorostrata. Similar to common minke whales, Antarctic minke whales are dark grey on the back with a pale ventral side. The main recognition character that allows for the distinction of Antarctic minke whales from common minke whales is the absence of a white patch on the flippers in Antarctic minke whales. The rostrum is narrow and pointed. The dorsal fin is hook-shaped and located about two-thirds the length of the body from the anterior. Baleen plates are black on the left side and on the posterior 2/3 of the right side, while the remaining baleen plates are white. The baleen plate filaments average about 3.0 mm in diameter. Antarctic minke whales have larger skulls than common minke whales.
Range length: 6.32 to 10.22 m.
Average length: Males: 8.36; Females:8.89 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger