Floating poop reveals secrets of whale evolution
Fecal samples reveal that whales herbivorous guts help them digest crustaceans
And analysis of what bacteria were present and what they could do led to a surprising insight into how gigantic whales make such a successful living from eating tiny aquatic crustaceans. They found that the whales, though now carnivorous, were using a suite of capabilities evolved when their ancestors were terrestrial plant-eaters.
They were using these systems, evolved to break down difficult to digest plant material, to break down the hard exoskeletons of their shrimp-like prey - material ordinarily discarded by most predators. This likely means the whales get about 10% more calories from their food than other animals get from the same diet - a bonus that likely helps explain how they grow so large.