European Rabbit (Photo Diliff, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0&gt;, via Wikimedia Commons)

Dear Readers, teeth are one of those things that are taken for granted until they rebel, at which point they become the most important things in the world. Is there anything more infernal than bad toothache? And who looks forward to a trip to the dentist? I’m fortunate enough to have my father’s teeth (and I can hear him in my head saying ‘isn’t it about time you gave them back?), which means that I have exactly one filling, and that put in by a lunatic evangelical dentist over forty years ago when I lived in Dundee. Well I remember him asking me if I had a relationship with Jesus while I had a mouthful of dental swabs. But anyhow, I was amused to have come across a trio of tooth stories in New Scientist in the past week or so, so here we go!

First up, rabbits apparently eat their own teeth in order to supplement the calcium that they need to grow new ones. Rabbits eat a very coarse diet, and their teeth are constantly wearing down – if they get too short, the rabbit can’t eat anymore. So, it seems that their teeth produce a fine calcium dust as the rabbit chews, and this is absorbed back into the rabbit’s body and digested much more easily than calcium supplements. It seems like a very sensible way to recycle a precious mineral, and who knew? Maybe not rabbit keepers, some of who have been feeding their rabbits calcium supplements that it turns out are unnecessary, and could, indeed, cause kidney stones.

Wild Bottlenose Dolphin from https://whalescientists.com/barataria-bay-bottlenose-dolphins-march-2022/

Next up, there is some speculation that dolphins can hear with their teeth. For a long time, scientists have wondered why dolphins have so many teeth – most of them aren’t used for chewing, and in addition they sit very loosely in the jaw. Scientist Ryo Kodera, of Tsurumi  University in Japan, suggests that the teeth might act as antennae, helping the dolphins to echolocate under water. The cochlear nerve, which processes sound, extends right into the lower jaw in dolphins, suggesting that vibrations felt in the teeth could be passed on to the brain. The teeth also sit in spongy, porous sockets which are connected by a thick bundle of nerves.

Other scientists are sceptical about this, but that is their job – Kodera acknowledges that there needs to be further research in future. At any rate, it seems that that beaming ‘smile’ of Flipper the dolphin might be about more than just healthy teeth.

Sabre -toothed cat (Smilodon fatalis) reconstructed at the Natural History Museum in London (Photo John Cummings, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0&gt;, via Wikimedia Commons)

And finally, why were sabre-toothed animals so successful, and why are there none today? When we think of such carnivores, we tend to think of the canonical sabre-toothed tiger, but actually these teeth evolved at least five times in different groups of animals. There were sabre-toothed reptiles some 270 million years ago, a sabre-toothed marsupial related to the extinct thylacine, and, of course, those cats.

Scientist Tahlia Pollock, of the University of Bristol, investigated the teeth of no less than 95 carnivorous mammal species including 25 sabre-toothed ones. The teeth were categorised, and then each set of teeth was 3D printed, and plunged into a block of gelatine that mimicked animal flesh.

The sabre teeth could puncture the block with 50 percent less effort than any other kind of teeth, and the Smilodon (pictured) had the most extreme teeth of all. However, there is a trade off to weaponry of this kind – the teeth were prone to breaking off, and some of the specimens found in the La Brea tar pits had lost teeth while they were alive.

Sabre-toothed predators were really designed to hunt giant prey, such as mammoths or giant sloths. But when these started to die out, the sabre-toothed animals were likely to have been outcompeted by carnivores with smaller teeth which were better adapted to smaller, more numerous prey, such as deer or rabbits.

So, today the sabre-toothed animals are gone, and instead we have smaller predators with smaller teeth to hunt smaller prey. Though if you’ve ever seen a tiger yawning, you might consider that the teeth are not that much smaller.

Links below:

https://www.newscientist.com/article/2464105-rabbits-may-eat-their-own-teeth-to-boost-their-calcium-intake/

https://www.newscientist.com/article/2461513-dolphins-may-use-their-teeth-to-hear-underwater/

https://www.newscientist.com/article/2463406-why-sabre-toothed-animals-evolved-again-and-again/