Spying on Whales: The Past, Present and Future of the World’s Largest Animals. Nick Pyenson

or how often and where these skeletons are likely to appear on the seafloor.

      A whale’s size would seem to play an important role for a unique ecosystem that is fundamentally tied to its carcass. After all, a larger dead body should provide more opportunities for whalefall specialists. It turns out that size doesn’t make too much of a difference where whalefalls are concerned, and the reason why we know has to do with the fossil record. As a graduate student, I had the good fortune to come across a fossil whale skull that had been collected a few decades prior, from rocks exposed on Año Nuevo Island, off the coast of central California. These rocks represent extremely deep-sea sediments about fifteen million to eleven million years old, and I didn’t think much about the fossil’s context until I was cleaning the skull in the fossil preparation lab at Berkeley’s paleontology museum and came across tiny clamshells nestled in crevices of the skull. They clustered together, almost lifelike, and I decided to pry one off for a closer look, after first documenting their arrangement. A mollusk specialist confirmed a possibility that had entered my mind: they were chemosymbiotic clams belonging to a family that specialized in whalefalls. In short, the fossil I had been preparing belonged to a fossil whalefall.

      Fossil whales with whalefall mollusks affixed to them had been found before and, while unusual, they weren’t earthshaking discoveries on their own. But what was different was that this skull belonged to a whale that would have been barely eleven feet long in life. Tiny baleen whales—much smaller than those today—were common during the Miocene, but the remarkable aspect of this find was that their small body size did not prevent the whale-fall from reaching the peak phase of sulfur-loving invertebrates. In other words, size doesn’t really determine the community that colonizes a whalefall ecosystem. If not, then what does? That’s still not clear, although it may be something about the lipids locked in the bones that controls which species can colonize the carcass, along with the stages of whalefall succession.