Is it true that the larger the ridge on the back of an animal's skull, the stronger the jaws?
Typically, yes. The temporalis muscle, one of the main muscles responsible for chewing, attaches to the sides of the skull. The bigger that muscle is, the more space it needs to attach and a large sagittal crest is a good indicator of an animal with exceptional mastication muscles. But there are other factors to consider when trying to determine the strength of an animal’s bite.
have especially large sagittal crests and very strong jaws to go with them but they don’t necessarily have a bite force that translates to being the strongest for their size in the animal kingdom. I read one study recently that said that fishers have a very similar bite force to that of red foxes and lynx, even with that enormous crest.
Gorillas, hippos, hyenas, and bears have some of the strongest jaws for mammals and I believe salt water crocodiles have the most powerful of all. But look at hyena and bear
skulls. They do have noticeable sagittal crests (kodiak, polar, and grizzly bears even more so than this black bear) but they also have large, strong teeth, thick zygomatic arches which are also where jaw muscles attach, an overall very dense bone structure, and massive neck muscles. All of that adds up to a devastating, bone-crushing bite.
What I like most about sagittal crests is how helpful they can be in identifying the sex of an animal. Male fishers like the one above can get huge crests, as do male sea lions, male gorillas, and males of many other species. Generally, the males of most species are larger and stronger than the females. Their bodies produce testosterone, a hormone that encourages the growth of larger muscles and with those larger muscles, like the temporalis, they’ll need bigger bone structures, like sagittal crests, to support them. How else are they gonna show off how fit and fiiine they are for the ladies (and the competition!)?
Below are a couple of examples.
Female raccoons (and subadult males but you can usually tell age by bone sutures) have smooth craniums while males typically have small sagittal crests. The fellow on the right here has one of the largest crests I’ve come across on a raccoon.
You can tell the gender of canid skulls similarly. Females can have smooth craniums but often they do have a fairly well-developed sagittal crest (dogs have very strong jaws) but it is never quite as pronounced as it is on male animals.
Here’s a pair of very large domestic dog skulls. The top I know for certain is from a male Rottweiler but the lower one’s history is unknown. But, based on the shape of the skull (not as wide through the eyes, smaller sagittal crest), I would bet that it came from a female dog.
These two skulls came from a male and female Carolina Dog. A friend of mine used to raise them and after these two passed he was kind enough to let me have their skulls.
These skulls are very similar in appearance but again, pay attention to the shape of the skulls. The female has a slightly smaller sagittal crest than the male and the male’s skull is wider and more robust in appearance.
Sexual dimorphism is apparent in the skull shape of many other species as well. The size of a sagittal crest is definitely one of the biggest giveaways on lots of carnivores and many omnivores. Not so much with herbivores but they often have handy-dandy tells like antlers and horns.
So there you go, Anon. Way more information than I’m sure you wanted, but hopefully it was helpful! Thanks for the ask!