Shark teeth offer clues to preventing extinction of threatened genus in Stanford Doerr School of Sustainability study

STANFORD, Calif. (KGO) — If you ever come face-to-face with the wrong kind of shark, there’s something you probably want to avoid. Just a hint: they’re long and really sharp.

But now, researchers at Stanford say those same razor-like teeth are offering critical clues about how threatened species may be different from their non-threatened relatives.

“There’s a lot of function in the shape of a shark tooth, because that’s really where the shark meets the world,” said Jonathan Payne, Ph.D. He is a researcher and senior fellow at the Stanford Doerr School of Sustainability.

He said subtle differences in tooth shape and characteristics can indicate key traits, ranging from body type to what the shark ate during its lifetime.

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“And because sharks have cartilage skeletons rather than bony skeletons, in the fossil record, the only part of the shark that’s really hard and preserves well is the teeth,” Payne said.

Lead author Mohamad Bazzi, Ph.D., compared 1,200 samples from roughly 30 species, including bull sharks and oceanic white tips.

All are members of a genus considered threatened by international experts.

But Bazzi said species with the most unique characteristics and feeding habits appeared to face the highest risk of extinction.

“And, what our analysis showed,’ he said, “is how extinctions act, not merely to reduce the number of species, but also the variety of species.”

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They say the greatest pressure on the shark populations is global overfishing. And if the pattern continues, it could result in the most common species becoming even more common, while the specialists disappear.

It’s unclear what consolidation could mean for specific ecosystems. But researchers point to the unintended consequences of events, such as the overhunting of sea otters off the California coast, which helped fuel a purple sea urchin population boom blamed for decimating local kelp forests.

“We also have more charismatic, if you like, large-bodied and pelagic species with apex predator roles, risking going extinct, such as the oceanic whitetip and the bull shark. These species, of course, help ocean ecosystems stay balanced and healthy. And their demise, we hypothesize, could have ripple effects in the environments that they live in,” Bazzi said.

They’re hoping the study will add urgency to international efforts aimed at protecting endangered shark species. Looking at past history, researchers believe conservation efforts and strict monitoring of overfishing could begin to stabilize shark populations, potentially over the course of just a few decades.