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Ursid Bite Force Studies
#1
Ancient bear had the strongest bite

By Ella Davies
Reporter, BBC Nature

[Image: _56455048_fossil-crop.jpg]
Scanning the skull revealed meaty secrets 

The largest bear that ever lived also had the strongest bite of any land mammal, say scientists.

Agriotherium africanum was a giant short-faced bear that became extinct five million years ago.

Reconstructions of the carnivore's skull revealed that it was well adapted to resist the forces involved in eating large prey.

By comparing the skulls of several species, scientists also found polar bears to have surprisingly weak bites. 

The findings were published in the Journal of Zoology.

Dr Stephen Wroe from the University of Newcastle, Australia and his team used CT scanners to create 3-D images of bear skulls. They scanned six species, ranging from a giant panda to a reconstructed fossil of A. africanum.

Using the computer generated models created by student Chris Oldfield, the researchers investigated how the skulls stood up to the forces that mimicked killing and feeding behaviours.

"Our analyses show that Agriotherium africanum had an enormously powerful bite - considerably greater than for the largest of living big cats, or any living bear," said Dr Wroe.

The extinct bear exerted the highest bite force with its large canine teeth. Of all the bears the team examined, its model showed the least strain through the skull when the researchers simulated the forces of biting an item of prey.

"Our analyses show that it had the most powerful bite of any known terrestrial mammal determined thus far," Dr Wroe told BBC Nature. 

[Image: _56454822_skull-stress-in-bite-at-can.jpg]
A comparison in skull stress for bears biting with their canines (a) A. africanum, (b) Asian bear, © black bear, (d) brown bear, (e) giant panda, (f) polar bear and (g) polar bear. Pink shows an area of high strain, while dark blue areas show no strain.

Results for another short-faced bear, the giant panda, were also notable; the animal's skull appeared to be well adapted to high levels of stress.

This might seem surprising for an animal with a diet strictly limited to plant material, but Dr Wroe pointed out that the panda had a large "grinding area" to chew through tough stalks of bamboo. 

In comparison, A. africanum had the smallest grinding area of the bears analysed.

The researcher said that A. africanum may have been a "hypercarnivore" with an unparalleled level of meat in its diet for a bear. 

"There has been considerable debate over the diet of A. africanum and other short-faced bears. Some have argued that these bears were more carnivorous than most living bears," said Dr Wroe.

"There can be no doubt that this beast had the power to kill almost anything it could get a hold of - it could also have chased any other predators off their kills; hence it could also have been a very effective scavenger."

"Its skull was well adapted to resist the forces that would have been generated under such extreme loads."

Fat-sucker 

The study also revealed that the polar bear was a surprisingly "poor performer".

"It has a really surprisingly weak bite for its size - arguably the weakest among living bears," Dr Wroe told BBC Nature.

He pointed out that these huge carnivores tended to target relatively "easy-to-kill", blubbery prey, such as seals.

"It might be more correctly categorised as a specialised 'fat-sucker' than a real meat eater," he said.

The skull comparisons revealed that the polar bear had much shorter blade-like teeth for ripping flesh than the supersized A. africanum.

These extinct giants lived in Africa at the end of the Miocene epoch and into the Pleistocene - five million years ago - and measured up to 2.7m in length.

http://www.bbc.co.uk/nature/15559929



Finite element analysis of ursid cranial mechanics and the prediction of feeding behaviour in the extinct giant Agriotherium africanum

C. C. Oldfield1, C. R. McHenry2, P. D. Clausen1, U. Chamoli3, W. C. H. Parr3, D. D. Stynder4, S. Wroe3,*
Article first published online: 20 OCT 2011

DOI: 10.1111/j.1469-7998.2011.00862.x

© 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London
Issue Journal of Zoology
Journal of Zoology
Volume 286, Issue 2, page 171, February 2012

Abstract
Historically, predicting ursid feeding behaviour on the basis of morphometric and mechanical analyses has proven difficult. Here, we apply three-dimensional finite element analysis to models representing five extant and one fossil species of bear. The ability to generate high bite forces, and for the skull to sustain them, is present in both the giant panda and the gigantic extinct Agriotherium africanum. Bite forces for A. africanum are the highest predicted for any mammalian carnivore. Our findings do not resolve whether A. africanum was more likely a predator on, or scavenger of, large terrestrial vertebrates, but show that its skull was well-adapted to resist the forces generated in either activity. The possibility that A. africanum was adapted to process tough vegetation is discounted. Results suggest that the polar bear is less well-adapted to dispatch large prey than all but one of the five other species considered.

[Image: oPfqedd.jpg]

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.2011.00862.x/full


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Journal Reference:
Grandal-d'Anglade, Aurora. (2010). Bite force of the extinct Pleistocene Cave bear Ursus spelaeus Rosenmüller from Europe. Comptes Rendus Palevol - C R PALEVOL. 9. 31-37. 10.1016/j.crpv.2009.10.003. 

Abstract
In this paper, I have made a theoretical calculation of the Cave bear’s bite force (BF) following
the “dry skull method” and I present for the first time BF data that can be of interest to
elucidate the mechanisms underlying the dietary choice of the Cave bears. In the skulls
studied, males show higher BF than females in absolute terms, but more similar with regard
to their body mass, which partly compensates for the smaller size of the females. The whole
sample studied shows lower BF in the upper carnassial than those of large cats, similar to
the one calculated for the Giant panda and higher than that of Polar bear.
[Image: wildcat10-CougarHuntingDeer.jpg]
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#2
Red Dog Wrote:
Quote: Here is the actual data below. It lists skull length, jaw-canine distance, temporalis and masseter musculature, lever arm lengths on these two jaw muscles, bite force and body mass. The panda appears to have a powerful bite because it has lots of jaw musculature and very long lever arms connected to them. Its snout is not short. The sun bear seems to have a good amount of jaw musculature and fairly long lever arms connected to them, but a very short jaw.

[Image: BearBiteForceData002Correction.jpg]

This figure may be a bit misleading for the brown bear as it lists average values (and the average brown bear skulls are not that large). Here is a graph of the above values - cross-sectional musculature, the lever lengths giving the jaw muscles mechnanical advantage, and the jaw length - for all of the individuals sampled:

[Image: BearCranialData003.jpg]

Here is another graph listing the bite force of all the specimens. It appears that very large brown bears have bite forces close to pandas.

[Image: BearCranialData004.jpg]
[Image: wildcat10-CougarHuntingDeer.jpg]
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#3
Here is another graph listing the bite force of all the specimens. It appears that very large brown bears have bite forces close to pandas.
A very large brown bear with greatesr/condylobadal? skull length under 40 cm?
Here is something wrong with that.
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#4
I believe the panda has a crushing bite while the polar bear has a slicing bite. Since the polar bear has the sharpest teeth of all bears, it might have the highest carnassial pressure of all bears in terms of canines.
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#5
Except for Oldfield et al (2012), the other studies posted here all used the 2D dry skull methods and thus they're not considered to be reliable by modern standards.

Even Oldfield et al (2012) has some issues regarding inconsistencies of their specimens measurements and body mass estimations. Thus, their conclusions may be a bit questionable.

Also, calling out the Polar bears for being a 'weak fat-suckers' while over-hyping Agriotherium as the ultimate apex predator is a bit of a stretch. In reality, it seems to be the opposite. Polar bears have been documented taking on absolutely huge preys. On the other hand, Agriotherium has forelimbs un-suited for grappling, Canines' root surface area are also small which suggests the Canines are not adapted for restraining struggling preys. Read this paper:
"Results show that in absolute terms, canine and carnassial bite forces, as well as root surface areas were highest in A. africanum. However, when adjusted for skull size, A. africanum’s canine roots were smaller than those of extant solitary predators. With teeth being the limiting factor in the masticatory system, low canine root surface areas suggest that A. africanum would have struggled to bring down large vertebrate prey. Its adjusted carnassial root sizes were found to be smaller than those of extant hard object feeders and the most carnivorous tough object feeders, but larger than those of extant omnivorous ursids and Ursus maritimus. This and the fact that it displayed its highest postcanine root surface areas in the carnassial region (rather than the most distal tooth in the tooth row) suggest that A. africanum consumed more vertebrate tissue than extant omnivorous ursids. With an apparent inability to routinely bring down large prey or to consume mechanically demanding skeletal elements, its focus was most likely on tough tissue, which it acquired by actively scavenging the carcasses of freshly dead/freshly killed animals. "
Tooth Root Morphology in the Early Pliocene African Bear Agriotherium africanum (Mammalia, Carnivora, Ursidae) and its Implications for Feeding Ecology

Yeah the ultimate predator, more like the ultimate scavenger. Polar bear is the only true 'ultimate predator' among the Ursidae. It's because of Oldfield (2012) that Polar bears suddenly have the reputation of being weak and unimpressive, which they're totally not deserved.
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#6
Thanks for that information. It somehow confirms my hidden suspiscion.
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#7
(03-18-2019, 03:12 AM)Old Tibetan Blue Bear Wrote: Thanks for that information. It somehow confirms my hidden suspiscion.
What are your hidden suspicions exactly? I may be able to help you solve some of them. Polar bear is my favorite extant Carnivoran so i did quite a bit of research on it. I'm actually intending to make a thread that will address some of the myths regarding this bear. However, i'm a bit tight on schedule atm. I personally think it's paradoxical how the largest and most powerful of all extant terrestrial carnivores is considered to be weak and unimpressive by many people. Except for having slightly weaker skulls than your average bears, there is not anything else about the Polar bears that are particularly 'weak'. And no, Polar bears are not lb 4 lb weaker than Grizzlies (post-cranial wise), they're are actually quite equal. Polar bears are pretty much what you would expect from a bear, they're not any stronger than a typical bear, they aren't any weaker either.
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#8
Quote:Except for having slightly weaker skulls than your average bears, there is not anything else about the Polar bears that are particularly 'weak'.

While I agree with your statements on the postcranial anatomy of the polar bear (and that they're not unimpressive overall), polar bear skulls are (far) more than just "slightly" weaker than normal. Polar bear skulls experience up to 5 times as much peak stress as the brown bear's skull when bone volume is similar and bite force is more or less equal (the polar bear ended up biting slightly harder in Slater et al. (2010), which is approximately consistent with Oldfield's results).
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#9
@Verdugo, the polar bear is my favourite land predator and animal too. My hidden suspiscion was that the short faced bear having poor grappling ability ( compared to other bears and felines) and has overestimated jaws strength (since its canine roots are not suitable to talking struggling prey as mentioned in your source). Your source also confirms polar bears taking down large prey (e.g. I posted a video on what a female polar bear's jaws can o to a beluga). Polar bears have the best slicing bite of all bears.
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#10
Quote:Bears are generally omnivorous animals, and will eat pretty much whatever is available. Although they look fairly fearsome, and do, of course, eat meat, they also consume a relatively large amount of plant material, such as berries, leaves, grass, nuts, and so on. This is useful, especially for a large animal, since they are unlikely to go very hungry for long, and plants are always more readily available than animals.


The polar bear (Ursus maritimus) is, of course, an exception. Unlike all other living bears, they feed exclusively on meat, and really don't eat plants at all. They are, to use the technical term, hypercarnivores, more similar in this respect to cats than they are to their own relatives. Nor do the differences end there. Most obviously, they are adapted to bitterly cold environments, and, indeed, they soon get heat stroke if taken to places that most other bears would be perfectly happy - anything much above 10°C (50°F) makes them uncomfortable. Not only that, but they are also much better swimmers than other bears, and have claws that grip into the ice when they walk.

Given these differences, you might think that polar bears represent an early branch from the lineage that led to all the other bears, one that adapted itself to both an extreme environment and a (for bears) unusual diet. But that turns out not to be the case, with polar bears having diverged from their closest living relatives, the brown bears, long after that line split from the other species.

 Polar      Brown     Sun Bear     Black
 Bear       Bear                   Bears
   |          |          |           ^
   |          |          |           |         Sloth Bear
   ------------          -------------             |
        |                      |                   |
        |                      |                   |
        ------------------------                   |
                   |                               |
                   |                               |
                   ---------------------------------
                                  |
                                  |  


Rather more surprising, perhaps, is just how recently this happened. Genetic analyses show that the first polar bears evolved no more than 0.7 million years ago, which really isn't very long in evolutionary terms - in contrast, most other species of bear diverged around 5 million years ago. In fact, its quite probably a lot less than 0.7 million years. The oldest known skeleton of a polar bear is only around 130,000 years old, which is sufficiently young to retain a good deal of DNA.When that DNA was analysed earlier this year, it seemed to show that the animal in question was so incredibly close to brown bears that it probably lived at around the time that the two diverged, and would therefore have been one of the first members of its species - a rare find, indeed.

What this means is that, after they first evolved, polar bears must have undergone a very rapid sequence of changes, quickly adapting themselves to their environment and new diet. Judging from the shape of their skulls, they must have changed at least twice as quickly as any other bear species did, and that's probably an underestimate.

How has the polar bear managed to adapt to a new diet in such a short time? Generally speaking, hypercarnivores such as lions tend to have strong skulls with powerful jaw muscles and large shearing teeth, suitable for slicing through tough meat and bone. This is much less true of bears, adapted as they are (in most cases) to a more omnivorous diet. But, compared with brown bears, polar bears have a long, rather sleek skull, which is even weaker than the heavy rounded skulls of their relatives. This is probably, at least in part, to make it easier for them to nuzzle through holes in the ice to catch seals.

Some recent stress analyses using the sort of computer models normally used in engineering design have shown that while the jaw muscles of polar bears are just as strong as those of normal bears, the skull itself is less able to take up the strain of a powerful bite. Granted, that's assuming the computer models are right, but even so, it does seem a bit odd. Similarly, while they do have less premolar teeth than many other bears (a feature they share with cats, for example), the teeth overall seem somewhat weaker than one would expect for a purely carnivorous animal.

One reason may be what the polar bears are eating. Their diet consists almost entirely of seals, which, unlike the antelopes eaten by lions, have a lot of soft blubber. If their food is less tough than the meat favoured by other hypercarnivores, they don't need such strong jaws, and the evolutionary change required to adapt to that diet may be less than it first appears. It may also help that, while animals like leopards and wolves regularly take down prey  larger than themselves, polar bears obviously don't. Seals just don't get that big!

There is, however, a clear downside to this rapid evolution and specialisation. As ice sheets melt, the habitat of polar bears is shrinking. But what's bad for them can be quite good for their relatives, the brown bears. Brown bears (Ursus arctos) are a diverse species, including both the grizzlies and Kodiak bears of North America, and the "common" brown bears of Europe and Russia, among others. They're pretty adaptable, and can eat a wide range of food, making them at home in dense forests, open woodland, or even tundra. As the polar bears' preferred environment shrinks, brown bears can move steadily further north.

The sort of things that brown bears eat are often tougher than seal blubber, and their teeth and bites are accordingly stronger. This means that, even if polar bears were to start eating such things (which isn't, perhaps, very likely in the first place), the brown bears would still do better. Brown and polar bears are still so closely related that they can interbreed to produce hybrids, at least some of which are apparently fertile. If that continues to happen, and the brown bears muscle in on the polar bear's territory, out-competing them for food, then it's the browns that will eventually win out, diluting the purebred polars into non-existence.
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#11
Quote:The sort of things that brown bears eat are often tougher than seal blubber, and their teeth and bites are accordingly stronger. This means that, even if polar bears were to start eating such things (which isn't, perhaps, very likely in the first place), the brown bears would still do better. Brown and polar bears are still so closely related that they can interbreed to produce hybrids, at least some of which are apparently fertile. If that continues to happen, and the brown bears muscle in on the polar bear's territory, out-competing them for food, then it's the browns that will eventually win out, diluting the purebred polars into non-existence.

The polar bear might have the weaker bite and skull can take less stress than a brown bear yet taking on and biting through a beluga and narwhale with skin that is 100 times thicker than the average mammal shows polar bears do have the best slicing bite of all bears. Its bite is still stronger than that of the sloth bear.
More info about bear jaws and teeth:


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#12
I never said a polar bear can kill pachyderms. All I said was the polar bear is able to slice through the skin of beluga, narwhale, and walrus not large whales and no it is definitely not a hippo, rhino, or elephant killer. Yet this topic is about bear jaw strength, if you disagree just say why.
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#13
(05-12-2019, 01:26 AM)OldGreenVulture Wrote:  ...beluga and narwhale with skin that is 100 times thicker than the average mammal...

^You wrote this. & I pointed out that 'pachyderms' are land animals of similar size, & they are per se, thick skinned.

AFAIR, U.maritimus uses its cranial/dental adaptations to suit its usual tasks in capture & butchery of seals.
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#14
Pachyderms are not your average land mammal. I guess I didn't elaborate on that:
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#15
So what?

Are beluga the average prey of U.maritimus, or indeed, are beluga even an average maritime mammal?
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