Post by Infinity Blade on May 3, 2020 2:18:16 GMT 5
I found data regarding jaw biomechanics for Arctotherium angustidens (Soibelzon et al. 2014; you can download the PDF on Google Scholar).
I've provided screen captures from the paper down below.
Mandibular force profiles for two specimens, particularly the relative force (Zx/Zy) was 0.83 in one specimen and 1.11 in another at the position of the canine. If I remember correctly (from what Ursus arctos from Carnivora said on the subject), the lower the value, the better the mandible is at taking stress. So these are some rather impressive strengths at the canine.
However, bite force and bite force quotient are...surprisingly low.
All these bite force estimates were via the dry skull method, so I think it's okay to directly compare these values. Despite rather high bite forces in absolute terms (even at the canine), it doesn't seem to have bitten particularly hard for its size. Absolute bite force at the canine was measured to be >1,000 N (this being a dry skull estimate, the real life value was likely greater), which sounds impressive...until you remember that the giant panda, brown bear, and the polar bear bit even harder, if anything. This is despite the fact that A. angustidens is twice as large as the polar bear, over 2.5 times larger than the brown bear, and over 5 times larger than the giant panda. Granted, the giant panda has a particularly powerful bite for its size, but the brown bear and polar bear evidently do not. So this thing had a mandible that could take far more stress than its bite force could ever reach. The extent of tooth wear seen in Arctotherium's teeth suggest a diet of tough food items like dried meat, bones, or rough plant material.
I'm not entirely sure why Arctotherium had such physically strong jaws but a relatively weak bite. I think the authors of this paper make more of a deal out of the absolute bite force than they should IMO (considering how it compares relatively speaking), but they do mention the hunting methods of the modern spectacled bear (the only living member of the Tremarctinae) against large prey. This bear ambushes the prey, immobilizes it with the forelimbs, and eats it alive by starting at the back; the prey dies from shock and stress. Alternatively, the bear chases the prey item through rough terrain, hillsides, or precipices, prompting it to fall possibly to its death. The authors suggest that giant short-faced bears like Arctotherium could have used the same strategies. Intuitively, I would guess that's possible; eating prey alive after immobilization might not need a relatively strong bite (although, T. ornatus has a vastly superior BFQ than A. angustidens, especially at the canines), and provoking it to fall to its death certainly doesn't.
I've provided screen captures from the paper down below.
Mandibular force profiles for two specimens, particularly the relative force (Zx/Zy) was 0.83 in one specimen and 1.11 in another at the position of the canine. If I remember correctly (from what Ursus arctos from Carnivora said on the subject), the lower the value, the better the mandible is at taking stress. So these are some rather impressive strengths at the canine.
However, bite force and bite force quotient are...surprisingly low.
All these bite force estimates were via the dry skull method, so I think it's okay to directly compare these values. Despite rather high bite forces in absolute terms (even at the canine), it doesn't seem to have bitten particularly hard for its size. Absolute bite force at the canine was measured to be >1,000 N (this being a dry skull estimate, the real life value was likely greater), which sounds impressive...until you remember that the giant panda, brown bear, and the polar bear bit even harder, if anything. This is despite the fact that A. angustidens is twice as large as the polar bear, over 2.5 times larger than the brown bear, and over 5 times larger than the giant panda. Granted, the giant panda has a particularly powerful bite for its size, but the brown bear and polar bear evidently do not. So this thing had a mandible that could take far more stress than its bite force could ever reach. The extent of tooth wear seen in Arctotherium's teeth suggest a diet of tough food items like dried meat, bones, or rough plant material.
I'm not entirely sure why Arctotherium had such physically strong jaws but a relatively weak bite. I think the authors of this paper make more of a deal out of the absolute bite force than they should IMO (considering how it compares relatively speaking), but they do mention the hunting methods of the modern spectacled bear (the only living member of the Tremarctinae) against large prey. This bear ambushes the prey, immobilizes it with the forelimbs, and eats it alive by starting at the back; the prey dies from shock and stress. Alternatively, the bear chases the prey item through rough terrain, hillsides, or precipices, prompting it to fall possibly to its death. The authors suggest that giant short-faced bears like Arctotherium could have used the same strategies. Intuitively, I would guess that's possible; eating prey alive after immobilization might not need a relatively strong bite (although, T. ornatus has a vastly superior BFQ than A. angustidens, especially at the canines), and provoking it to fall to its death certainly doesn't.
