Being slow swimmers, they were an easy catch, even for whalers in frail wooden boats that were equipped with only handheld harpoons. Besides, unlike other whales, right whales float when they are killed because of their extraordinary amount of blubber.
Turklāt atšķirībā no citu sugu vaļveidīgajiem dienvidu gludvaļi savas ārkārtīgi biezās tauku kārtas dēļ pēc nogalināšanas uzpeld ūdens virspusē.