Some fish-eating orcas have worn out teeth: Here's why

Worn-out teeth, also called tooth wear, are pretty common in cetaceans. Although there are many documented cases of tooth wear in captivity, worn-out teeth exist in wild whales. And especially those who eat a lot of fish, like herring-eating killer whales. In this post, we explain why eating some fish can damage wild killer whale teeth.

Eating sharks or sucking on small fish can wear out killer whale teeth – Credit: Anaïs Remili.

Shark scales cause some major damage

Extreme tooth wear (down to the gum) could be caused by the denticles (scales) and cartilaginous bodies of shark species like the sleeper shark. Indeed, researchers believe that some offshore killer whales in the Northeastern Pacific feed on sharks in the open ocean. Shark denticles are tiny flat V-shaped scales covered externally by a layer of a hard enamel-like substance called vitrodentine. This structure makes shark skin pretty rough and sand-paper. As a result, the constant rubbing of the scales against killer whale teeth sands them down until nothing is left! This phenomenon is not rare in offshore killer whales: several studies mentioned extreme tooth wear in stranded whales. Such bad teeth could cause infections in wild orcas if the gums get cuts.

Slurp! Sucking fish can destroy killer whale teeth

On the other side of the world, we can find killer whales with moderately to highly worn-out teeth in a different ocean. Norwegian killer whales like to munch on Atlantic herring; it is their main prey. Herring is a small fish: 20 to 38 cm (8 to 15 in), covered in scales. Killer whales have large mouths and between 40 and 56 interlocked teeth. Their sharp teeth are not made for chewing but for ripping and tear their prey before swallowing it in chunks. So how do Norwegian killer whales eat herring? They suck it! Literally, and because they slurp many of them, the scales rub against the whale’s front teeth and gradually damage them until they ultimately wear off (after many years, of course).

So what is safe to eat for good teeth?

Extreme tooth wear was not really observed in North Pacific resident killer whales because they feed mainly on larger fish like the chinook salmon (61 to 91 cm – 24 to 36 in), which they tear into large chunks before swallowing. Similarly, North Pacific transients and North Atlantic killer whales that feed on marine mammals have minimal tooth wear because they do not scrap scally prey against their teeth. Although no whale isn’t at risk of breaking a damaging their teeth accidentally, it seems that tearing the food rather than sucking it helps, and scales are riskier than mammal skin.

Sources and further reading

Loch, Carolina, and Paulo C. Simoes-Lopes. “Dental wear in dolphins (Cetacea: Delphinidae) from southern Brazil.” Archives of Oral Biology 58.2 (2013): 134-141.
Ford, John KB, et al. “Shark predation and tooth wear in a population of northeastern Pacific killer whales.” Aquatic Biology 11.3 (2011): 213-224.
Foote, Andrew D., et al. “Ecological, morphological and genetic divergence of sympatric North Atlantic killer whale populations.” Molecular Ecology 18.24 (2009): 5207-5217.

Thank you for reading! Did you learn something new? You can check out our other posts on killer whales:

Third newborn for Southern Residents: Killer whale baby boom

Anaïs Remili

Website

Anaïs is the founder of Whale Scientists. She is a PhD student at McGill University working on killer whale ecology and pollution. You can read more about her here.