New Study Suggests Prehistoric Walrus Was a Fish-Eater

A new study on the fossil of a prehistoric walrus suggests that the animal was not a deadly killer, but more of a fish-eater.

The fossil of an ancient walrus, named Pelagiarctos, was first discovered in the 1980s in the Sharktooth Hill bone bed of California. Pelagiarctos lived some 15-18 million years ago during the middle Miocene period.

Earlier analysis of a part of the jaw bone and sharp pointed teeth of the walrus made researchers believe that the animal was a top predator, feeding on large prey like birds and marine mammals.

But the discovery of a more complete specimen, including a complete lower jaw and teeth, in the Topanga Canyon Formation near Los Angeles has suggested that the animal was just a fish-eater. When researchers analyzed the new specimen and the original fossils, they found that the teeth of the prehistoric species were not sharp enough to feed on larger prey. Instead, they suggest that the animal feasted on fish and other invertebrates.

"When we examined the new specimen and the original fossils, we found that the teeth really weren't that sharp at all - in fact, the teeth looked like scaled up versions of the teeth of a much smaller sea lion. This told us that the tooth shape is really just a consequence of Pelagiarctos retaining primitive teeth, rather than being a feeding adaptation," researcher Robert Boessenecker, from the University of Otago in New Zealand, told the PLOS ONE Community Blog.

Further, Boessenecker and his colleague Morgan Churchill of the University of Wyoming determined the body size of the walrus based on the size of the animal's lower jaw. They found that the walrus was large in size, similar to that of modern-day sea lions.

However, researchers point out that the body size of an animal does not have any correlation with its food consumption. Animals like modern-day walruses and sea lions, those belonging to the pinniped family, are known to feed on fish rather than large predators. This trend suggests that the ancient walrus was just a fish-eater and not a deadly killer, they told the Community Blog.

The findings of the study appear in the journal PLOS ONE.