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Morphological comparison: big cats & brown bears; originally posted by Ursus Arctos
Topic Started: Jan 9 2012, 07:18 PM (6,413 Views)
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This entire thread is old and outdated. I wrote it years ago, when I first started reading journal articles. I have learned much since then. I will eventually begin work on updating it.
See the thread muscle info: strength and flexibility, as well as pages 3 and on of carnivore limb robusticity study if interested in much more educated interpretations. Or better yet, read "Muscle Architecture in Relation to Function" by Carl Gans (you can find it as a free download via google), as it explains why many interpretations are wrong. Also, bite info is questionable to-more accurate 3d bite force estimates have not supported the results of 2d estimates regarding big cats vs bears in biting ability.
-Ursus




This is the post I promised Peter I would make.
Rather than simply reposting the old post, or copying large parts of it, I figured it would be most helpful to simply make a new post.
The old one was primarily made to refute irrational claims by a certain poster-such as "bears are simple"-and thus was somewhat geared towards attacking this poster's credibility. These remarks obviously aren't necessary, and the post would be much better at providing info if it is simply direct. This requires redoing the post.
As (I think) a comprehensive post was desired, adding more sources and info (some of which I didn't have at the time) requires typing new comments anyway.

The post will be divided into two sections, each of which will all be divided into two subsections.
The organization is as follows:
Postcranial morphology
-Grappling ability
-Cursorial ability
Cranial morphology
-Bite force
-Canines

Postcranial morphology
Grappling ability
First of all, elbow flexibility (from “Locomotor Evolution in the Carnivora (Mammalia): evidence from the elbow joint”, by Ki Andersson):
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The PC2 values are of the trochlear notch's depth; the depth of the elbow joint.
The lower the value for PC2, the shallower the notch. The more shallow the notch, the more flexible the joint is.
Specifically, the values for elbow flexibility is the degree to which the animals can supinate and pronate their forearms. Basically, the lower the PC2 value, the greater the flexibility with which an animal can rotate it's paws to hold, push, etc, an animal with which it is grappling.
Much more information on this a little later, including pictures of the trochlear notch.

Olecranon:
Some articles measured simply the length of the olecranon, while others (like Valkenburgh) measured the distance between the end of the olecranon and the center of rotation, so this can lead to some discrepancy, especially when differences in joint sizes are large.


Now, an explanation as to what the relative olecranon length is (taken from Van Valkenburgh's article "Skeletal Indicators of Locomotor Behavior"):
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The triceps is the primary (or only I think) extensor of the forearm; if two animals have triceps muscles of equal strength, and one had an olecranon 20% longer relative to the rest of the ulna, that animal would be able to extend it's forearm at the end of the ulna with 20% greater force, but it would extend 20% slower.
Now, one obvious issue here is that, for a plantigrade bear, after the end of the ulna is the wrist and the paw. For a tiger or other digitigrade animal, the metacarpals are also part of the length of the limb. This means that if both have equal relative olecranon lengths, the brown bear would have the greater leverage at the paw.

Relative olecranon length is normally looked at to indicate ambushing behavior or digging abilities. Animals like badgers have relatively very long olecranons to aid in digging.
Among normal terrestrial (rather than fossorial) animals longer olecranons are associated with ambushing behavior, as it increases acceleration when coming out of a crouched position.

In the study "Forelimb indicators of prey-size preference in the Felidae" (also by Van Valkenburgh) relative olecranon length was associated quite strongly with a preference of relatively larger prey. This suggests that longer olecranons help in subduing and grappling with bigger, stronger animals, and that thus greater ability to extend the forearm aids in grappling.
-The fact that the large prey specialists were heavier than the medium prey specialists, who were heavier than the small prey specialists, however also suggests the possibility that this was simply a consequence of size. As muscle strength scales with area, and body mass with volume, the larger cats would need greater mechanical advantage (and/or larger muscles) to compensate for their larger size in order to be able to stalk and then accelerate as they ambush as effectively.

Here then is the data from “Skeletal Indicators of Locomotor Behavior”:
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Boris Sorkin's measurements (from “Ecomorphology...bear-dogs...”; data on brown bears and pantherines same in each):
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The values (here rounded after only a few decimal places because copying and pasting from the calculator creates some stupid tags on openoffice that I then have to go through the trouble of deleting):
Ursus arctos gyas male: 62/358= 0.173

Ursus arctos horribilis male: 46.5/281.5= 0.165

Panthera tigris altaica female: 69/269.5= 0.256

Panthera tigres ssp. male: 55.5/214= 0.259

Panthera leo, both sexes: 52/261.8= 0.199

Panthera onca, both sexes: 45/192.6= 0.234

Panthera pardus, both sexes: 40.8/188= 0.217


Here is the data I read from the “article I read quiet some time ago”:
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It was called “Forelimb ratios of 22 North American carnivores”, or something like that.
As it states, the value for OL is simply the log, so it is easy here to determine the ratios:
Male brown bear: 0.16405897731995392752
Male cougar: 0.18071741260109270729
The cougar is fairly modest compared to the pantherines in the olecranon length according to Van Valkenburgh's data.

I honestly don't know what to say in the face of inconsistent data; the best I can come up with is to go with the majority (brown bears having relatively short olecranons).
One curious fact is that long olecranons are commonly associated with animals adapted towards digging (such as badgers), and while the brown bear has a few adaptations towards the purpose (including front claws much longer than rear claws, and the shoulder hump) this would mean that the olecranon apparently is not one of them.
It has now been several days with no further replies, meaning until I (or someone else) gets a reply, or someone finds more data (Peter, perhaps you could make some measurements if you get to look at a few ulnas from these species at a museum?), the best recommendation I can have is to simply reject Valkenburgh's data.

Here is a summary of the description of the olecranons of a few animals (if requested I can post the actual quotes) in the article “Morphofunctional analysis of the postcranium of Amphicyon major from the Miocene compared to U arctos P leo and C lupus”, by Christine Argot:
The bear's olecranon looks shorter (I don't think they were measured) than that of the other animals thanks to “the proximal extension of the lateral lip of the anconeal process”.
Amphicyon has a noted medial protrusion of the olecranon which is much more emphasized in the bear than the other two carnivore species, but its “relationship to the development of a specific muscle is not clear”.

Relative length of the deltopectoral crest:
The deltoid and pectoralis muscles attach to the humerus on the deltopectoral crest (a crest that forms for increasing surface area for muscle attachment, similar to the sagital crest). Along with a relatively longer crest implying more muscle (which would also be implied by a more pronounced crest), the further the end of the crest is from the joint, the more mechanical advantage the muscles that attach their will have.
These muscles are crucial to the ability of a feline to subdue large prey (crucial to grappling ability):
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From "Ecomorphology of the giant bear-dogs Amphicyon and Ischyrocyon" by B. Sorkin.
Data from that same article:
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And data from "Ecomorphology of the giant short-faced bears Agriotherium and Arctodus" by the same author:
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Data on the big cats from the first:
American lion: 236.3/373.3=
0.63300294669166889901

Lion: 188.3/290.2=
0.64886285320468642316

Leopard: 121.6/194.4=
0.62551440329218106996

Cave lion: 167.8/286.7=
0.58528078130449947681

Siberian tiger: 191.1/308.3=
0.61985079468050600065

Panthera tigres sp: 160/253.6=
0.63091482649842271293

Male lion: 201.5/315.6=
0.63846641318124207858

Lioness: 174/278.4=
0.625

Lioness: 175/264.8=
0.66087613293051359517

Siberian tigress: 208/314=
0.66242038216560509554

Female Panthera tigress sp: 185.5/303.4=
0.6114040870138431114

Female Panthera tigress sp: 180.5/303.2=
0.59531662269129287599

Ursus arctos gyas male: 335/444=
0.7545045045045045045

Ursus arctos gyas female: 237/324.3=
0.73080481036077705828

Ursus arctos ssp: 291/383=
0.75979112271540469974

Ursus arctos horribilis male: 243/336=
0.72321428571428571429

Ursus arctos syriacus male: 235/300.5=
0.78202995008319467554

Lion average: 0.64330134982911052423
Tiger average: 0.6239813426099339593
Brownie average: 0.75006893467563333047
The brown bears from this sample had ~16.5% greater mechanical advantage than the lions and ~20% more than the tigers. This means that if they all had equally powerful deltoid and pectoralis muscles, the brown bear would be able to move the end of it's humerus with 16.5% and 20% more force respectively. This is however most likely not the case; judging by pictures, some brown bears appear to have the most massive of these muscles for their size, and are on average quite impressive (in most other species, it is only the exceptionally powerfully built individuals that develop shoulder humps, such as the tiger Madla).
Here is a picture of the humeri from the “Ecomorphology....Arctodus” article:
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You can clearly see the relatively extreme prominence of the crest further down the humerus of the brown bear. While the crest of the tiger is small past about around the ~50% point before it ends, the brown bear's is large for heavy muscle attachments up until just before the end of the crest. It is also great that you can actually see the shape of the elbow joints of the tiger and brown bear.
For comparison, the distal end of the humerus of a wolf from the same angle (taken from Ki Andersson's elbow morphology study; the same as the source for the PC2 values):
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More information from the same source (Andersson):
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The trochlear flange of the tiger does look bigger than that of the brown bear (or at least, straight rather than bent away), although the overall PC2 value was still lower for the bears. I'm under the impression here that bears sacrificed yet further stability for increased elbow flexibility compared to pantherines (who did so compared to hyenas/cursorial canids). It also sounds like the stability the pantherines retained is stability relevant to grappling with prey though. Without more information, I don't think we can interpret this further than that.
A quote covering prey-killing abilities of Arctodus compared to Ursus arctos, from B. Sorkin's “Ecomorphology of...Arctodus”:
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The first paragraph has just been covered, while the second would complement the data on elbow flexibility, discussing strength with which they could pronate their forearms, and strength with which they can control their wrist/paws.
The above picture comparing the humeri is the figure 11 quoted above. Here are a couple of pictures taken from wikipedia labeling the medial epicondyle:
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I think that of the brown bear looks a little larger than that of the tiger.
From “Morphofunctional...” by Christine Argot:
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Brown bears evidently have some advantages, however:
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This suggests lion>brownie in rotational ability of the paw.

When considering the mechanical advantage of the movement of the humerus, the other limb segments must (again) be considered, although in this case it is perhaps less relevant (as I doubt these animals will be holding their arms straight while trying to grapple). From Sorkin's study:
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I have however seen values of up to 0.9 for brown bears, although I think these were generally smaller bears. The metacarpals would then also have to be considered, and again, these are not a part of the bear's limb, while they do add additional length to the limbs of the felines.

Some info from “Morphofunctional...” by Argot suggests the muscle attachments of some muscles related to the rotation of the humerus are stronger in lions (and wolves) than in the brownie:
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Info on size of forearm flexing muscle attachments from the same source as above:
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From “Building a Mammalian Superpredator” by Stephen Wroe:
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In my opinion the most interesting value above is “Rt/Re”.
This value is for the mechanical advantage of the bicep muscle. If two animals have equally powerful biceps, and one has a higher Rt/Re value, it will be able to flex the end of it's radius with greater force. This also once again means that when it comes to flexing, the relative force at the paws is overestimated for felines (as they have an additional length of limb segments).
The values are log(x+1), where x is the actual ratio. Therefore, to find x, we must simply do 10^value - 1.
So the values are:
Sun bear: 0.17219536554813046614559376200578
American black bear: 0.17489755493952954172206776512684
Brown bear: 0.15611224219209884832575567525884
Lion: 0.16680961706096251647088848858969
Jaguar: 0.2078138351067801926325889031707
Leopard: 0.16949939101987098193722100197643

Bears and big cats appear to be overall fairly similar in this value, but all these large felines have greater mechanical advantage of the biceps than the brown bear, suggesting that they may have greater pulling ability given equally sized biceps (if the extra length of their additional limb segments doesn't deflate the functional value).

Some other information above that is interesting when it comes to the forelimbs includes RI/HI (radius/humerus, more data to go along with that from Sorkin above), and RI (robusticity index: body weight/body length).
One can see here that the brown bear used in this study had a longer radius relative to the humerus than either of the two earlier ones from Sorkin's data; in the above it was 0.923.
Info on the calculation of the robusticity index:
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I am not convinced by the accuracy of the robusticity index, as it seems like their may be some room for mistakes. Personally, I do not find trichosurus, the brushtail possum, to be significantly more robust than other animals in it's size range (as the data suggests the case is).
However, among the articles I looked through, I only found two with information on tiger body length and body mass as well as that of bears. While the first suggested bears were far heavier for their given body length (brown bear weighed much more with shorter head-body length), that source's data seemed also open to question. At the very least because the figures for brown bear weight were seasonal averages; for our purposes I'd thin spring or summer figures (when they have relatively low body fat) would be best. The other was Van Valkenburgh's data from “Skeletal Indicators of Locomotor Behavior”, included in the olecranon section above, which contains log head-body lengths as well as log body weight. The body weight values there were, again, taken from literature.
Therefore, I'll leave off any judgments/conclusions here until someone finds the time to compare data on length and mass of the animals. Only body length (excluding head and neck) would probably be most ideal for comparisons (I don't think neck length should impact robusticity values).
Mc3/Hl (metacarpal length/humerus length) could be used to estimate the extra length of the feline's extra limb segment.
That of the lion is 0.368, meaning that the metacarpals add on an extra 36.8% the length of the humerus onto the end of the limb.
Some time later I may try and use this data to more accurately compare actual mechanical advantage of both animals, but considering the relatively high number here, it seems like bears would then end up with quite an edge.
Actually, I think this means I really do have to go back quite badly because such a difference will have a huge impact on the results. As of the November 11, 2010, edit of this post I have not.

Edited by Ursus arctos, Aug 21 2012, 02:27 AM.
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Info on the shoulder morphology:
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It is very hard to say how much of this is really a comparison relative to the non-bear animals, and how much it is simply a fact-I'm sure lions have powerful deltopectoral muscles, etc. This is why it is important to look at the discussion section:
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“The scapula of A. major exhibits such a fossa, as well as a wide scapular neck, much more similar to that of bears than to any other carnivore” makes it sounds like the scapular neck is wider in bears and Amphicyon than the modern lion (still no idea how it compares to Smilodon).
I don't see any info comparing the size of the spinati, other than mentioning that the infraspinous fossa is bigger than the supraspinous fossa in bears, while they're roughly equal in lions and wolves.
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Although I guess relative to the length of the scapula, that of the bear has the largest spinati-although these images are not to scale (so for all I know the scapula of the bear could be shorter for it's size). Although that brown bears have among the largest shoulder muscles is already well known I'm sure, considering even average specimens generally having a distinctive shoulder hump only developed by the more impressive specimens of other species (although some other factors do accentuate the appearance of the hump in brownies, it is primarily shoulder muscle).
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The brown bear's joints didn't have to move in a parasagital plane, I assume, in contrast to the lion?

Hind limbs (from “Functional-adaptive features and paleobiologic implications of the postcranial skeleton of the late Miocene sabretooth borhyaenoid Thylacosmilus atrox (Metatheria)”, by Christine Argot):
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Unsurprisingly, the hips of bears allows them to rear up much better than the hip of felines.

Spine:
From “Morphofunctional analysis of the postcranium of Amphicyon major from the Miocene compared to U arctos P leo and C lupus”, by Christine Argot.
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In head-rotating ability, Amphicyon and P. leo > U. arctos.
I'm not sure about other capabilities; according to the poster Dinocrocuta those areas of the skull colored red:
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Are areas for neck muscle attachment (brownie on left, American lion on right), where in general bears seem to have a large advantage. I'm not sure about the function of that flange though.

Thoracolumbar vertebrae means dorsal vertebrae; it just combined the words for thoracic (the vertebrae with ribs) and lumbar (the ones that bend, and often aid when a quadruped runs).
Some more info from the article's discussion section:
P. leo has 13 thoracic vertebrae and 6 lumbar vertebrae.
U. arctos has 14-15 thoracic vertebrae and 5 lumbar vertebrae.
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The spines of felines have more powerful muscles to aid in acceleration and running speed, as well as greater mechanical advantage, while that of bears lacks flexibility at those angles.

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The above picture from “Ecomorphology...Arctodus” by Sorkin.
Muscle attaches to the spines coming out of the vertebrae; from these pictures it is easy to notice the different angle of the spines in the brown bear, tiger, and wolf. In the brown bear the spines are laterally projecting, while in the tiger and wolf they're angled much closer in the antero-ventral direction.
An explanation from “Building a Mammalian Superpredator” by Stephen Wroe:
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While the antero-ventrally angled spines allow for powerful bending of the spine in the antero-ventral direction to power explosive acceleration, the laterally directed spines of the brown bear allow for powerful lateral bending of the spine, such as can be seen in this video after the 30 second mark where the fight begins (especially at ~0:36, and then a little later at 0:42 when one bear finally brings the other down). This ability combined with the hip and foot adaptations that allow for standing on the hind legs allow for the integration of a large number of different movements into a single powerful push to throw the other animal over.
The shorter spines of the bear imply that the side to side bending isn't as powerful as the ventral flexing of the spines of modern felines (or the extinct Smilodon)-but they're in a much more useful direction.
The lower LV/TV values (relatively shorter lumber vertebrae) of bears also increases stability on hind limbs.

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Brownies have greater epaxial musculature. As these muscles are attached to the hips and the ribs, it seems as though these muscles would power the bending of it's spine from side to side.
A picture of the hips to get an idea of the degree of outward deflection of the anteroventral tip:
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Reddhole considers ml diamter of the humerus/humerus length to be a good indicator of how powerfully built an animal is.
Brown bear: 0.108
Lion: 0.0892
Tiger: 0.0857

Cursorial ability
Covering the spine info first, so that it doesn't have to be reposted as it is directly above: as the quote by Dr. Wroe states, the antero-ventrally oriented processes allowed for relatively explosive acceleration and greater top speed to aid in hunting prey. Relatively longer lumbar vertebrae also aid in running ability, allowing the flexing of the spine to provide a greater contribution to stride length (relative length of vertebrae segments data provided in the data from Dr. Wroe's “Building a mammalian super-predator”). In the same vein, lower RI (robusticity index) would then also suggest a more cursorial animal (longer spine compared to body weight). Wroe's data from “Building...super-predator” is also reposted again a little lower in this post.

PC2 values again:
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And the quote explaining relevance for cursorial ability:
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The more hinge-like the limb, the more efficiently the animal can run. Bone rather than muscle to provide stability also allows the forearms to be thinner (note: allows means potentially, not necessarily), aiding in running efficiency (consider ungulates who lack any pronating/supinating ability).

Limb proportions:
Limb proportions are much more useful for predciting cursoriality than they are for predicting relative grappling ability. For grappling ability the actual strength/mechanical advantage are crucial, and limb proportions often don't do that good of a job reflecting this. They do better reflect specializations in regards to running ability, such as stride lengths, however.
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The data from “Ecomorphology...Arctodus”.
The difference in tibia/femur is very large, and doesn't really come close to featuring any overlap between the bear's values and that of the lions or tigers.
It is also interesting to note that Arcotodus, a less cursorial animal than the modern brown bear also has less grappling ability for it's size; less cursorial does not mean a better grappler as that example demonstrates.
Dr. Wroe's “Building a mammalian super-predator” contains more info on proportions:
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Fl/Mt3 (femur length/metatarsal length; note that Van Valkenburgh's “Skeletal indicators...” also includes the femur-metatarsal ratio for those wanting to look further) has also often been correlated with cursorial ability. While this value may appear biased by the fact that bears are plantigrade rather than digitigrade, this fact alone very strongly suggests what the relative cursorial adaptations are of these species. The lower the value, the more cursorial the animal. As you can see, the fact the brown bear has the lowest value of the included bears, conforming with the fact that it is the fastest of the bears.
Lack of severe bias seems to be confirmed by the fact that despite being plantigrade bears do not have exceptionally high values compared to other families-after all, despite being plantigrade, bears are not exceptionally slow.
Mc3/Hl is similar (metacarpal length/humerus length), although as the more distal limb segment's length is divided by the more proximal one, here higher values means more cursorial. I have no idea what reasons may be behind this inconsistency in which length is divided by the other, but as it doesn't have any impact on the results I guess it doesn't matter.
Here the sun bear has a higher value than the brown bear, although the brown bear's Mc3/Hl is much higher than the slower black bear.
The felines also again have adaptations suggesting greater cursorial ability.
LV/TV is the relative length of the lumbar vertebrae column compared to the presacral vertebrae columb, and has already been mentioned at the beginning of the cursoriality section (and before in the grappling section, too). While the brown bear actually has the lowest value of the bears, the fact that the bear's spine doesn't contribute much to their running performance, as has already been mentioned when discussing the angle of the spines/processes, suggests that the longer lumber vertebrae of the other bear species doesn't aid in running speed.
Fa/Fm is described as mediolateral/anteroposterial femoral midshaft width. I think the description was a slight error: it would be Fm/Fa if it were mediolateral/anteroposterior.
A greater anteroposterior width compared to mediolateral suggests a more cursorial animal, meaning a higher Fa/Fm means more cursorial. The fact that the description was what was wrong is confirmed by comparing the values of the cursorial animals, such as the hyena and African wild dog with other animals. The brown bear again has the highest value among the bears, and interestingly has a higher value than the jaguar.
The Fa/Fm value measures resistance of the humerus to propulsive forces (which would act on the anteroposterior plane) versus other, more random, forces.

If it has been forgotten since it was mentioned the first time, Rl/Hl is radius/humerus. Here the brown bear is ahead of a couple of felines, although still behind the only pantherine also included by Sorkin. To bad Wroe didn't include measurements on the tiger. The brown bear is (again) the most cursorial of the bears.

One is free to un-transform the values for comparisons, although as of yet I haven't done that here. I will likely go back and edit in more in depth comparisons in the future.

I think shorter olecranons may be more associated with cursorial ability, as the animals that run down their prey tend to have relatively short olecranons (cheetah, grey wolf, African wild dog...the spotted hyena, like it almost always is when it comes to the upper arms-note that I'm referring to the mechanical advantage of the triceps when I saw upper arms here, even though the olecranon is part of the ulna-is a blatant exception).
Longer olecranons help with accelerating explosively from a crouched position when ambushing. It seems that in a short chase the extra acceleration from the greater force relative to muscle size is more important than the lower top speed of forearm extension.

Hind limb structure also shows that lions are more cursorial (From “Morphofunctional...” by Christine Argot):
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Cranial Morphology
Bite force

First of all, for anyone who likes to criticize the credibility of the bite force studies utilizing the “dry skull method” (such as those produced by Dr. Wroe, Per Christiansen, and some others), one should consider the fact that these are all peer reviewed articles using sound methodology. As far as I am aware, while it is very popular among posters who aren't fond of the results to challenge their credibility, it is preferred by researchers.
Tests, such as those often put in documentaries, were a bite force meter is handed to an animal are comparatively very lacking in credibility, due to a huge number of confounding variables, ranging from motivation of the animal to bite down, and the ability of it's teeth to bite down onto hard surfaces.
The very robust carnassials of hyenas, for example, are much better adapted to biting hard objects (such as bones) than felines, and also use some kinetic energy as well, to break them.

To summarize the dry skull method, they calculate the muscle cross section area of the various muscles that power the jaws, as well as the mechanical advantage of all these muscles (sometimes at more than one point; the 2007 article by Wroe calculated it both for the carnassial econes and the canines, for example). This allows for very accurate comparisons of the actual forces the animals are physically capable of biting with if need be.

Note that different studies can use different values for the amount of force the muscles produce relative to their muscle cross section area, so it is not recommended that one compare force estimates (in Newtons) between studies without first making sure the same value is used.
The studies by Wroe also, for convenience, calculate bite force quotients (BFQ). These are also not to be compared between studies, as these are values meant to compare the animals within the study, were a value of 100 is the average of the sample of included species (as with other quotients).
BFQ is also done so that when two animals are scaled to the same size (considering the 2/3rds allometric rate of muscle cross section area/body mass) the relative differences in their bite forces would be equivalent to the relative differences in BFQ. This means that if one animal has a BFQ of 127, and another 100, if both were the same size the first animal would bite 127/100= 1.27 times, or 27%, harder.

The biggest issue with the dry skull method is that their can sometimes be a great deal of individual variation; very mature, yet still prime aged, males will have much more impressive-wide-skulls than younger animals. This is true for bears, raccoons, and likely many other species as well (probably more true for animals that aren't extremely regular big game hunters). Bite force studies may have more respectable sample sizes than the tv documentary bite force meter studies.

From “Bite Club: comparative bite force in big biting mammals and the predatory behavior in fossil taxa”, by Stephen Wroe, Colin McHenry, and Jeffrey Thomason (from 2005):
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The above is bite force at the canines.
Comparing brown bears to pantherines of equal weight:
Tigers bite 63% harder.
Jaguars bite 76% harder.
Lions bite 44% harder.

From “Bite forces and evolutionary adaptations to feeding ecology in carnivores” by Per Christiansen and Stephen Wroe (from 2007):
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Comparing brown bears to pantherines of equal weights at the canines:
Tigers bite 31% harder.
Jaguars bite 19% harder.
Lions bite 25% harder.

Please note that brown bear bite forces don't simply go down with each new study (as Warsaw said sarcastically); this study was simply a bit of an anomaly by not saying brown bears are blown completely out of the water.

From “Bite force of the extinct cave bear Ursus spelaeus Rosenmueller from Europe”, by Aurora Grandal-d'Anglade:
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This study suggests that at equal weights to the brown bear the lion and tiger bite with about 100% more force.
It looks like cave bears have a similar bite force relative to size as brown bears; they're about 3 times heavier, meaning they should have around twice the bite force, similar to that of lions and tigers. 3^(2/3)= ~2.0.

Per Christiansen did a bite force study exclusively on bears (Evolutionary implications of bite mechanics and feeding ecology in bears); here are the results:
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It is clear that the difference in bite force produced by lions and tigers compared to brown bears is very significant.
When comparing one bear with another that is 50% larger, assuming both have a similar bite force for their size, the larger one will bite about 31% harder (1.5^(2/3)=1.31037...), in order to provide an idea about how truly significant even such a modest difference in bite force is (as between brown bears and tigers from Wroe's 2007 study).
A bear twice the size of another that has a similar bite force for it's size would bite just under 60% harder, and a bear three times larger would bite about 100% harder.
Depending on which of the above studies is accurate, this would then mean that a brown bear fighting a similarly sized tiger would basically be matched against the jaws of a bear either half again larger, twice his own size, or even three times heavier than himself!
As one can see, comparing the power of their bites is a mismatch.

Canines
Great info on skulls, including gape (the article says these values may be conservative, using pictures of yawning clouded leopards as a reference to suggest living animals are apparently able to obtain a wider gape than what was measured when opening a skull and trying to keep the joints alligned), and dimensions of both the upper and lower canines including length, anteroposterior width, and mediolateral width of canines came from “Bite forces, canine strength and skull allometry in carnivores (Mammalia, Carnivora)” by Per Christiansen and Jan Adolfssen:
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The upper canines of the lion and tiger were over 50% longer, and their lower canines about 35% longer.

The strength of the canines is also something crucial to consider:
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Bear and feline canines have similar strengths relative to their bite forces. This means both can bite with the same percent of their total vigor, although for the lions/tigers this would be far greater vigor and far more massive teeth. Thus, the statement “this would then mean that a brown bear fighting a similarly sized tiger would basically be matched against the jaws of a bear either half again larger, twice his own size, or even three times heavier than himself!” isn't entirely accurate: the canines will be even larger, and the bigger jaws can still bite just as freely.
This study by Christiansen didn't compare bite forces to size, but instead to the strength of the canines. Hence, this study having only been brought up in the canine section.
Here are those values, for reference (including cross section areas of the two primary muscles powering the jaws; info on the mechanical advantage of these muscles is provided in the first table I posted from that article):
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A different study by Christiansen, which focused on Ursids (Feeding ecology and morphology of the upper canines in bears (carnivora: Ursidae)), provided a lot of details on Ursid canines:
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He also, again, compared the bending strengths of the canines with bite force values (the ones he had calculated in his earlier article focusing on bear bite forces). If posters are interested I could post the lengthy descriptions, but their relevance to this thread are limited due to the lack of comparison with felines, and only between bears. A basic summary: pandas have relatively weak canines compared to their bite force, while sloth bears and sun bears have relatively strong canines relative to their bite forces. In the case of the sloth bear, this is largely due to having a relatively low bite force.

Finally, if there is anything in this post that you don't fully understand or needs clarifying, I would be more than happy to spend my time explaining, as otherwise I'd have wasted all of it on typing this post up!
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coherentsheaf
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This is an impressive amount of data, thank you for compiling it and explaining it in such a comprehensive way.
Since it seems relevant I will post my comparative plots between long bone dimensions and body mass between felids and ursids, bone abreviations as in the limb robusticty thread:

Extant felids range in weight from 1 kg (black footed cat) to 230kg(amur tiger) and ursids range from 20kg(female sun bear) to 700kg (large polar bear) giving an overlap from 20kg to 230kg.
The inverted power law would be long_bone_dimension=(mass/a)^(1/b).
Note this equation is possibly not an optimal equation, however a few geometric properties of the line in the log log plot show that it should be reasonably close for most datasets.
Since only the ratios felid/ursid should be important and they are variable with mass I plotted them in the range of 20-230.

HL:
http://imageshack.us/photo/my-images/202/hlursidfelid.gif/

HC:
http://imageshack.us/photo/my-images/40/hcursidfelid.gif/

HW:
http://imageshack.us/photo/my-images/341/hwursidfelid.gif/

FL:
http://imageshack.us/photo/my-images/717/flfelidursid.gif/

FC:
http://imageshack.us/f/708/fcfelidursid.gif/

FA:
http://imageshack.us/photo/my-images/193/fafelidursid.gif/

As a final note I would like to add: As far as I know bears have more body fat than felines, maybe we should adjust for that when comparing bite force and other traits..
Edited by coherentsheaf, Jan 31 2012, 01:30 AM.
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Ursus arctos
Autotrophic Organism

Thanks for adding.

I am planning on eventually revising the presentation and adding a lot more info, making it even more comprehensive.

The organization could use some work, but the explanations in particular need a lot. Whether I want it to simply exist as a list of extracted references about both species, or actually want it to explain and go beyond that is also something I would need to decide.

A lot of published, relevant, info wasn't included-there is a lot to dig through and find. Some articles are also very poorly translated, and going to be painful to try and add in a more readable, understandable, manner to the revised thread.

coherentsheaf
 
As a final note I would like to add: As far as I know bears have more body fat than felines, maybe we should adjust for that when comparing bite force and other traits..


Body fat levels vary depending on individual, population, time of
year, and year:
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Unfortunately we do not have comparable info on any big cat species. Body fat percentages of wild bears are of specific interest to researchers, due to the distinct physiological phases (especially hibernation) and associated yearly fluctuations.
For big cats, they normally use much cheaper and easier estimates of body condition (and often with bears as well).
-On that note, while we may associate low body fat with athleticism, the most impressive bears and big cats will, being the healthiest, probably have above average for their species at that given time.

The best I could find was a reference to a pregnant lioness (no info on whether wild or captive) with 13.1% body fat.
It is likely that in general lions have a little less body fat than brown bears even in midsummer.
Captive bears may be more likely to put on a lot of fat though.
Sample sizes were small that produced the equations for those graphs, so I would like to try and find more.

As far as bite forces go, there is something I need to update. It was pointed out to me by a poster that the weight estimates for the species may often be unreliable-for example, in Wroe's 2005 article the the brown bear was given a body mass far out of proportion of the skull size for the populations info was presented on. BFQ thus not representative in that case.

-Much more extensive analysis and comparisons needed all around.
Edited by Ursus arctos, Feb 2 2012, 01:25 AM.
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coherentsheaf
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@Ursus: I did not mean to compare their body fitness by adjusting for body fat. I was thining that the point of your comparison was to compare felids and ursids of comparable skeletal and muscular frame. In this case using total body mass would be like comparing a smal kid with a big backpack and a normal kid with a normal backpack and declaring the slim kid to have particulary slender bones for its size. Therefore it coud be hepful to adust for the body fat of both species.

Furthermore we often cannot be sure in what stage the bears in the studies were, which could skew data quite heavily, since least squares regressions tend to oervalue measurements that are far fromthe usual line.
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Ursus arctos
Autotrophic Organism

To be honest I am not entirely sure what the point was. Ultimately, the ideal would be to compare them at similar body mass.

Comparing them at similar skeletal frame would likely in general be better. It is much easier to do, understand, and follow.
Body mass isn't really related to many of the ratios-be they proportions or mechanical advantage.
Even when talking about indicators of relative muscle size compared to limb lengths (i.e. Epicondylar index) smaller lengths relative to body mass may then indicate greater leverage by a similar margin (assuming actual measurements of muscle attachment distances aren't available), as with the greyhound - pitbull comparison.

Quote:
 
In this case using total body mass would be like comparing a smal kid with a big backpack and a normal kid with a normal backpack and declaring the slim kid to have particulary slender bones for its size. Therefore it coud be hepful to adust for the body fat of both species.


I agree, for bears IMO it is important to note what time of year the body mass figures came from.

Even when bears do not have high body fat percentages proportions can differ.
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Update on my search for epicondylar index info, I haven't found or gotten leads on quantified info at the moment.
Picture lifted from Sorkin's 2006 article on the Ecomorphology of Giant Short Faced bears (can also be seen above):
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Relative to humerus length the width of the epicondyles, and size of the deltopectoral crest, in the brown bear are visually apparent-even if he did not provide any measurements of the former.

I have however found no shortage of articles to read, so no real problem on my end. Just another of the many informative measurements!
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Gregoire
Omnivore
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great comparison - two of the most dangerous group of species.
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brotherbear
Unicellular Organism
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Taipan says: This entire thread is old and outdated. I wrote it years ago, when I first started reading journal articles. I have learned much since then. I will eventually begin work on updating it.
*I have hopes that this future project has not been entirely forgotten.
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LionClaws
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I hope that those images haven't been lost forever...
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Taipan
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brotherbear
Dec 7 2016, 09:18 PM

*I have hopes that this future project has not been entirely forgotten.


This was a thread I transferred over from the old Carnivora (Proboards version) that was originally posted by Ursus Arctos.

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Ursus arctos
Autotrophic Organism

Those images were all hosted on imageshack and have therefore been lost.
The actual journal articles the screen shots were quoting still exist.

Apparently I planned on editing / revamping this four years ago.
I had more time then, and all these articles were fresher on my mind.

EDIT:
I made a few posts this last summer (you can see July, August, and September; just scroll to the long ones; those in Ask a Question & Get a Proper Answer and Polar Bear V Leogorgon kilmovensis in particular).


Bigger news as far as updates go:
Early this month I started messing around with the data from here, and started building a model relating peak strength vs strength over a range of motion in elbow-extension.
The big news is, within Felidae, it definitely looks like longer olecranon correspond to strength over flexibility.

I think I'll end up with something worth publishing, but if not it should still interest some posters here.
Hopefully I'll return to that later this month or in the first week of January.
Edited by Ursus arctos, Dec 21 2016, 04:55 AM.
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