Comparing grappling ability of extant Ursids

[Silver]

Hello there, im new to this forum as my first thread ill post an study for grappling ability of extant bears, I got this from domain of bears so credit goes to person who first posted it there

Among the hunting strategies employed by members of the order Carnivora (Mammalia), two, stalk and ambush and sustained pursuit, are particularly prevalent among larger species of the order. It has been difficult to identify morphological traits that support this distinction and ecological observations have shown that most carnivorans adopt a continuum of strategies, depending on available habitat and prey. In this paper, the shape of the distal humerus articulation is analysed, with the aim of exploring the use of the forelimb in prey procurement, and as a guide to such behaviour among fossil carnivorans. The results suggest that manual manipulation and locomotion are conflicting functions. Elbow-joint morphology supports a division between grapplers (i.e. ambushers) and nongrapplers (i.e. pursuers). Joints of the former are characterized by being relatively wide and the latter, by being relatively narrow and box-like with pronounced stabilizing features. At intermediate and large body sizes, carnivorans show a pattern suggesting mutually exclusive feeding strategies that involve either grappling with prey or sustained pursuit. The former allows for large body sizes, such as pantherine felids and ursids; the latter includes species of only moderate size, such as hyenids and canids. Elbow-joint morphology is closely linked to phylogeny, but the morphology of the cheetah converges with that of nongrapplers, showing that strong selective forces may override the phylogenetic component. Two taxa of giant mustelids from the Miocene were analysed to test whether this sort of analysis is applicable to carnivorans of the past. The African Late Miocene species Ekorus ekakeran has a joint morphology comparable to that of modern-day nongrapplers. Two joint morphologies were found in the North American Late Oligocene-Early Miocene Megalictis ferox.

The first morphology is comparable to that of modern pantherine cats and the second forms an intermediate between grapplers and nongrapplers that is not present in the modern carnivoran fauna."

Reading through the abstract you will realize that the author divides the species in two groups: grapplers (ambushers) and nongrapplers (pursuers). A grappler's forelimbs are characterized by wide and strong stability features which are helpful at tackling large game. The author determined a value for measuring the ability to subude, manipulate or excavate food items, a so called "PC2-Value", here is a personal comment from the author himself:

"Scoring intermediate or low on PC2 are carnivorans that use their forelimbs to subdue, manipulate or excavate food items. Among these are ursids, mustelids, procyonids and felids. Although not being full grapplers, intermediate scores on PC2 characterize small canids. Small canids and small grapplers do not, however, overlap and all canids score higher than other carnivorans of the same body mass."

This means that a lower PC2-value is signalizing better dexterity/flexibility in a species' forelimbs and the ability to adapt itself to problematic angles or problems in general that might occur when manipulating/subduing their prey item. Unfortunately they excluded the Asian black bear and the sun bear in this study, so I will just rank the other six species from lowest to highest (note that a lower value means being superior in this case):

1. Polar Bear: -7.999
2. Brown Bear: -7.045
3. Spectacled Bear: -6.517
4. Giant Panda: -6.034
5. American Black Bear: -5.521
6. Sloth Bear: -4.447

Other Species:

Lion: -0.531
Jaguar: -1.713
Leopard: +1.072
Cougar: +1.633
Grey Wolf: +10.470
Spotted Hyena: +8.006
Wolverine: -1.356
American Badger: -0.859

Heres the source:https://www.researchgate.net/publication/228546271_Locomotor_Evolution_in_the_Carnivora_Mammalia_Evidence_From_the_Elbow_Joint Reply

[Verdugo]

I posted these data some times ago on a different forum, perhaps I could copy them to here.

1. Differential scaling of the long bones in the terrestrial carnivora and other mammals
   
Humeri AP and ML Robustness:
American Black bear (i'll just throw ABB here for the sake of comparison): AP: 10.96%; ML: 9.71%; Total: 20.67%
Brown bear: AP: 11.76%; ML: 10.84%; Total: 22.6%
Polar bear: AP: 11.95%; ML: 9.83%; Total: 21.78%

In this study, Polar bear is more robust in AP while Brown bear is more robust in ML. Overall robustness of Brown bear is higher than that of Polar bear.

2. Scaling Patterns and Ecological Correlates of Postcranial Skeletal Robusticity in Canis and Ursus: Implications for Human Evolution
   
Humeri robustness (mix-sex):
American black bear: AP: 11.10%; ML: 9.65%; Total: 20.75%
Brown bear: AP: 10.84%; ML: 9.97%; Total: 20.81%
Polar bear: AP: 12.32%; ML: 9.77%; Total: 22.09%

Similar to the study above, Polar bear is more robust in AP while Brown bear is more robust in ML. Overall robustness of Polar bear is higher than Brown bear

3. Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, Arctodus simus, Revealed by Traditional and 3D Landmark Morphometrics
   
Average humeri AP and ML robustness (measured by HAPW/HL and HMLW/HL respectively)

American black bear: AP: 11.50%; ML: 10.00%; Total: 21.5%
Brown bear: AP: 10.60%; ML: 9.80%; Total: 20.4%
Polar bear: AP: 12.50%; ML: 9.75%; Total: 22.25%

Similar conclusion to other 2 studies above, Polar bear is more robust in AP while Brown bear is more robust in ML. Overall robustness of Polar bear is higher than Brown bear

Overall, it does seem like Polar bears do have higher humeri AP robustness than Brown bears do while Brown bears have higher humeri ML robustness. High AP robustness would be more resistant to stresses from for-backward direction (AP direction) while high ML robustness would be more resistant to stresses from side to side (ML direction). Reply

[Verdugo]

I made this comparison some times ago on a different forum, I'll copy it here for backup.

   
I scaled several Carnivorans' humeri to similar length, so that their robusticity and muscle attachments points could be compared in relative terms.

Sources:
Ursus spelaeus
Ursus maritimus
Amphicyon ingens
Ursus arctos (Pleistocene)
Smilodon populator and Panthera tigris altaica
Arctodus simus and Ursus arctos gyas
Machairodus lahayishupup
Panthera spelaea Reply

[peter]

(08-14-2024, 01:08 PM)Verdugo Wrote: I made this comparison some times ago on a different forum, I'll copy it here for backup.


I scaled several Carnivorans' humeri to similar length, so that their robusticity and muscle attachments points could be compared in relative terms.

Sources:
Ursus spelaeus
Ursus maritimus
Amphicyon ingens
Ursus arctos (Pleistocene)
Smilodon populator and Panthera tigris altaica
Arctodus simus and Ursus arctos gyas
Machairodus lahayishupup
Panthera spelaea

Nice. Also like the sources (reliable). 

Anything known about the difference between bones of Pleistocene big cats and those of today? And what about today's bears and big cats? In what respects do they compare and in what respects are the differences most outspoken? Most likely reasons? Reply

[Verdugo]

(08-15-2024, 07:58 AM)peter Wrote: Nice. Also like the sources (reliable). 

Anything known about the difference between bones of Pleistocene big cats and those of today? And what about today's bears and big cats? In what respects do they compare and in what respects are the differences most outspoken? Most likely reasons?

Hi Peter, glad you enjoy my post.

I was not going comment anything about this comparison cause I made it quite some times ago and posted on a different forum. I posted it on WF primarily to backup it case it will be deleted on the other forum cause it did take me some efforts to make this, and also hopefully some folks at WF would appreciate it.

However, if you want my inputs... I can't comment too much on Pleistocene Big Cats cause I have not been researching on them for quite some times. I guess one thing that is quite apparent in this comparison is the robusticity of Pleistocene Big Cats, especially the Cave lion, in comparison to extant Pantherine such as Siberian tiger. The humerus's diaphysis of Cave lion is markedly more robust than that of extant Pantherine, being more or less comparable to those of large bears such Polar bear or Alaskan brown bear. Higher robusticity means that the bone has a higher safety factor and thus less prone to structural failures when under loads. Robusticity is a function of size, larger animals simply have relatively more robust bones to help them compensate for exponentially increase in mass due to square cube law. However, the humerus of Machairodus lahayishupup, while being more robust than that of extant Pantherine, is still less robust than Cave lion, even though Machairodus is a very large cat itself. Thus, I reckon the increase robusticity in the Cave lion is probably also related to the need of withstanding the stresses from grappling with larger prehistoric preys.

With regards to Bears and extant Pantherines comparison, the humerus of Bears are markedly more robust than that of Pantherines, both at the diaphysis and especially at the distal epiphysis. Since robusticity is a function of size, and the bears in the comparison (Polar bear and Alaskan brown bear) are so much larger than the Pantherine (Siberian tiger), the greater robusticity of the diaphysis is expected. The wider distal epiphysis is probably to due to the fact that Bears generally have wider articular area which allows them to have more range of motion at the elbow such as pronation and supination. One thing that also stands out is the relatively longer and more pronounced (and rugose) deltopectoral crest in Bears in comparison to Pantherines. This suggests more distal attachments of muscles attached to crest such as deltoid, pectorales, cleidobrachialis, and thus higher mechanical advantage for force productions, at the cost of speed. While in Pantherines, the crest is moderate in length, suggests a balance system of both speed and force. Another thing that also stands out is the more developed lateral supinator ridge in Bears when compared to Pantherines. The ridge provides origins area for muscles related to flexing the elbow and supinate antebrachium. So I reckon these functions should be quite strong in Bears.

Also, I'm trying to be brief, of course there are a lot more to unpack with regards to anatomical comparison between Bears and Big Cats. However, I'm planning to post more Bears vs Bears comparison rather than Bears vs Big Cats cause there are already a lot of those on the Internet. Perhaps, I could make dedicated posts to compare Bears and Big Cats anatomy at some points if I'm feeling motivated, but probably not in near future. Reply

[Verdugo]

I posted these data with regards to Canines comparison between Polar bears and Brown bears on a different forum some times ago, will copy it here.

1. Canines:
See Per Christiansen (2008) Table 2 for data on the canines of several species of Ursid.
   
Here are some relevant comparisons that I would make:

a. Canines Crown Height: I use Canine Height / Skull Length to make body-size-adjusted crown height comparison
Polar Bear: 0.133
Brown Bear: 0.132

Summary: When body size is adjusted, the crown height of these two bears are comparable.

b. Canine Crown Bending Strength: I will compare bending strengths at two points, at the alveolus and at 45% of crown height.
I use the following calculation to make body size-adjusted canine bending strength:

Sml(Avl) * 10^4 / Skull Length^2: size-adjusted bending strength about medial-lateral axis at the alveolus.
I use squared Skull Length to adjust for square-cube law since strength values Sml and Sap are measured in mm^2. The 10^4 is added there to make the values not to 'decimal' (i hope that makes sense)

Polar Bear: 2.084
Brown Bear: 1.948

Sap(Avl) * 10^4 / Skull Length^2: size-adjusted bending strength about anterior-posterior axis at the alveolus.
Polar Bear: 1.515
Brown Bear: 1.335

Sml(45%) * 10^4 / Skull Length^2: size-adjusted bending strength about medial-lateral axis at 45% of crown height.
Polar Bear: 1.014
Brown Bear: 1.186


Sap(45%) * 10^4 / Skull Length^2: size-adjusted bending strength about anterior-posterior axis at 45% of crown height.
Polar Bear: 0.887
Brown Bear: 0.961

Summary: Polar Bear's canines are stronger proximally (at alveolus). Brown Bear's canines are stronger distally (at 45% of crown height). This is probably due to the fact polar bear's canines are thicker at the alveoli but then become sightly more tapered distally.

c. Canine Root Strength, determined by canine root surface area:
See Alejandro Pérez-Ramos et al (2018) Table 2.
   
The value Ca RA-sa is relevant to our purposes because it is size-adjusted.
Polar Bear 1: 0.40
Polar Bear 2: 0.43
Brown Bear: 0.38

Summary: when size is adjusted, Polar bears have thicker, an thus more reinforced canines root. Reply