The baleen of a Pygmy Blue Whale
Image: Ken Walker & Simon Hinkley
Source: Museum Victoria
Question: What is the difference between baleen and toothed whales? Exactly what is baleen?
Answer: Baleen whales are passive filter feeders with no teeth. Instead of teeth they have flexible plates of dense bristles (called baleen slats) attached to their upper jaws. Baleen is a unique material made of keratin – the same substance as human fingernails.
When they feed, baleen whales fill their mouths with sea water and use their powerful tongues to push the water through the baleen plates and out of their mouths. The baleen acts as a filter: as the water passes through the baleen, tiny organisms living in the sea water are trapped against the bristles and then swallowed. These small food items are mostly plankton, krill and small fish.
Toothed whales, on the other hand, are active predators that each much larger prey. They use their teeth to catch and hold their prey and generally swallow it whole.
The presence and absence of teeth and baleen is not the only difference between the toothed and baleen whales. Baleen whales are generally large in size with huge jaws, despite their tiny prey items. In fact the Blue Whale, a baleen whale that feeds almost exclusively on krill, is the largest animal alive today. The toothed whales are generally smaller and have smaller, more streamlined jaws. The other major difference between the two groups is that baleen whales have two external blowholes whereas toothed whales only have one.