Don’t judge a whale’s gut microbiome by diet alone

Baleen whales totally skimp on their veggies, feeding on schools of fish and krill, but the whales share gut microbes with both meat eaters and vegetarians, researchers report September 22 in Nature Communications. 

Researchers combed through poop samples from baleen species, searching for DNA that might hold clues to the types of microbes that inhabit their guts. That turned up genetic codes for proteins helpful for digesting meat, suggesting that whale guts house some similar microbes to those found in fellow carnivores.

But other whale gut microbes looked more like those found in cows, hippos and other land herbivores. That’s probably because, like cows, whales have multiple stomach chambers — inherited from their land mammal ancestors. This unusual digestive structure impacts the microbial populations that help whales gradually digest chitin, a carbon compound in tiny crustacean skeletons (a small fraction of the whale diet), the researchers suspect.

The findings add to evidence from giant pandas that evolutionary history and diet both shape the microbes that live in animals’ guts.