Bear Strength

[Roberto]

(10-30-2019, 02:18 PM)johnny rex Wrote:

(10-06-2019, 10:11 AM)Polar Wrote:

(09-05-2019, 05:15 PM)johnny rex Wrote:

(02-02-2019, 07:07 AM)GrizzlyClaws Wrote: Dog got pinned several times by a Black bear cub.

Bears can be said as natural born wrestlers. Just look at how male bears fight with each other. Those "paw swipes that break bones" stories maybe are just exaggerations, bears tend to use their forelimbs to hold and wrestle prey or competitor to the ground not swiping hard.

Those might not really be exaggerations. Depending on where they hit, a bear's super-dense paw may actually break the shoulder, chest, or pelvic area of a weaker big cat since they have greater radial robusticity and bone density than the feline. Radial robusticity (think of a wide-framed man throwing a hook) increases impact from the side with greater hip rotation.

If you mean "a weaker big cat" like a sick lion or tiger, smaller big cats such as a jaguar, a leopard, etc. yes maybe. Is there any book or source that said bears have greater bone density?

yeah, actually there is:

The following study details carnivore limb bone lengths and widths, which we can use to infer both limb and overall body robusticity.



Credits to Reddhole or Leopjag

Source: Bertram and Biewner, "Differential Scaling of Limb Bones in Terrestrial Carnivores and Other Mammalia", Journal of Morphology: 204 157-169: 1990



For years posters have debated the overall strength of individual species. Commonly people post pictures of individual animals that purport to show that one species is stronger than another. Unfortunately, these picture comparison are unscientific in that the individual animals could have thick fur, the pictures can be taken at flattering or unflattering angles, or the photos may be photoshopped.



A more scientific approach involves limb bone dimensions. Scientists have found that limb lengths and widths (especially humerus or upper arm bone and femur or upper leg bone) correlatate strongly with body mass. Of the two, limb bone width is generally the better measure because wider bones can support more body mass. Thus, an animal with relatively wider bones is usually a stockier and therefore more powerful animal (although individual muscles may not be).


This study details humerus, femur, radius (forearm bone), and tibia (lower leg bone) lengths and two measures of width - anterioposterior diameter (AP diameter) and mediolateral diameter (ML diameter). Another study in which Ursus and I have posted extracts before found that animals that run fast (cursors and ambushers to a lesser extent) tend to have relatively wide AP diameters in their limb bones compared to animals that run at lower speeds or less often (i.e bears, mustelids, etc.). Here is the relavant extract:


[img]https://i.imgur.com/SURl5dY.jpg" class="lozad max-img-size" alt="" title="">

*This image is copyright of its original author

For example, the cheetah has relatively robust limbs if we use AP diameter, but rather gracile limbs if we use ML diameter. As a result, I think ML diameter is the better measure because it leaves out limb bone thickening due to high speed running.



The humerus and radius robustness measures are also interesting from a grappling perspective. Animals that grapple with heavy prey tend to develop a relatively more robust humerus and radius to handle the high stresses involved in handling large prey. In fact humerus and radius robustness were two key morphological traits of cats that kill large vs,. small prey in the feline grappling study I posted a few months back.


The study used several mature adult specimens with roughly equal numbers of each sex when possible. I do not think sexual dimorphism should play much of a role since another study of feline limb bone dimensions did not show much change in relatively limb robusticity between sexes of each species.

*This image is copyright of its original author

Another thing to note is that animal limb bones become slightly more robust as they get larger all else being equal. The trend is not too significant until animals reach about 100-300 KG.


Below is the raw data. Also, note we can calculate radius/humerus and tibia/femur (i.e. mechanical advantage of the forearm and lower leg - lower values mean stronger forearms and more stable rear legs all else being equal) from this data.

*This image is copyright of its original author

*This image is copyright of its original author

Here are some general observations - mostly based off of ML diameter of the humerus (i.e. ML diameter of humerus/humerus length) unless otherwise noted.


1) The bears are extremely robust, even the smaller species, which should not have extreme thickening of the limb bones that larger species do. Most have humerus's as or more robust (based off of ML diameter) than any big cat.



Sun Bear: 9.6%

Sloth Bear: 11.67%

Black Bear: 9.7%

Giant Panda 9.7%



2) Lion and Tiger


Lion: 8.92%; 12.78%



Tiger: 8.57%; 11.37%



The lion has a more robust radius and tibia based off of ML diameter while the tiger's radius and tibia is more robust based off of AP diameter.



As most already know, the tiger has the lower (i.e. more advantageous) radius/humerus and tibia/femur ratios. Reply