The pygmy right whale is an enigma in the whale world. Not only is it the smallest of the characteristically large filter-feeding baleen whales, but it's also rarely sighted and seldom studied -- partly because of its inconspicuous nature and resemblance to minke whales. But new research led by UNSW Sydney analysing chemical clues hidden in the jawlines of pygmy right whales confirms what scientists have long suspected -- these majestic aquatic mammals behave quite differently to their much larger whale relatives. The research, published in Frontiers in Marine Science, suggests the pygmy right whale is one of the few whale species to forgo long-distance migrations to Antarctic waters and instead reside in the temperate waters near Australia throughout the year.
Studying an animal the size of a whale in a lab -- even a relatively small species like the pygmy right whale -- is challenging. Instead, scientists can analyse the composition of smaller tissues that keep detailed records of an animal's activity. For filter-feeding whales like the pygmy right whale, long, slender keratin bristles called baleen plates that hang from their upper jaw allow them to take in many small prey like krill -- but they also lay down chemical signals called stable isotopes that give researchers hints about their behaviour.
For the study, the researchers analysed the stable isotopes in the baleen plates of 14 Australian pygmy right whales. Each baleen plate, loaned from the South Australian Museum, contained up to three to four years' worth of data to assemble a picture of the pygmy right whale's diet and movements across nearly 40 years -- the most extensive study of the pygmy right whale diet and movement to date. The researchers also found some evidence the whales' feeding patterns were linked to oceanic changes that drive food web dynamics in the region, specifically upwelling events -- natural cycles bringing nutrient-rich water to the surface, resulting in increased krill availability in Australian waters. The researchers say their findings help lay the foundation for more research that can help us better understand the pygmy right whale.
