Sharp claws helped ancient seals conquer the oceans

When catching and eating large prey, top predators use tools like sharp teeth and strong claws to tear apart their food. Such weapons are common in predators on the land, but in the water, animals like seals and whales are better known for having streamlined flippers that help them swim.

Clawed forelimbs likely helped ancient seals like Enaliarctos to eat large prey, just like the living northern seals. Credit: Illustration by Kai Hagberg.

New international research published today in Royal Society Open Science has shown that this isn’t always the case, with one group of marine mammals - the northern seals - still using their strong claws to tear apart their prey.

“We usually think of seals as having flippers for swimming,” said one of the study’s lead authors, Dr David Hocking, a Postdoctoral Researcher at the Monash School of Biological Sciences.

“But we’ve found that species like harbour and grey seals use their paws to grasp prey while feeding,” he said.

To learn more about how these animals feed, Dr Hocking collaborated with researchers from the University of St Andrews and the Alaska SeaLife Center to make detailed first-hand observations of how these animals use their teeth and claws.

“We found that the seals routinely tore prey into pieces small enough to swallow by stretching it between their teeth and claws,” said co-lead study author, Associate Professor Alistair Evans, also from the Monash School of Biological Sciences.

The team then compared the hand bones of modern seals to those from a 23 million-year-old fossil seal, Enaliarctos mealsi, which was discovered in California in 1975 and is now held by the Smithsonian Institution in Washington DC.

“We found that modern seals share many features in common with their early ancestors, including flexible finger joints and strong claws,” said Dr Hocking.

“This suggests that like modern northern seals, these early fossils seals would have been able to use their claws to help them hold prey”.

These behaviours may have been important when seals first started feeding in water, helping them to eat large prey at a time when they may not have been quite so well suited for aquatic life, according to Associate Professor Evans.

“Most modern seal species, including fur seals, sea lions and the Antarctic seals, have lost or reduced the size of their claws, possibly as their limbs became more important for swimming,” said Dr Hocking, “so it is interesting that one group of seals, the northern seals, have retained this ancient anatomy.”

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