Comparing Cats: A Discussion of Similarities & Differences

[SpinoRex]

The clavicles(or collar bone) of lions and tigers

The clavicle, also known as collar bone or clavicula is the bone that connects rib cage and arm (from Sternum to Scapula), serving as strut. The Deltoid, the Trapezius, the Pectoralis Major as well as several muscles of the throat are attached to it. Bigger muscles attached to the clavicle necessitate overall larger clavicle size which will, in return, limit flexibility of the arm. That means strength and flexibility of the arms develop inversely and that animals with larger clavicles likely have stronger pectorals and shoulders while animals with smaller clavicles are more flexible.


The results regarding lions and tigers are suprprising on the one hand but as expected on the other hand. The study included 9 lions (5 males, 1 female and 3 unsexed specimens) and 7 tigers (6 females and one unsexed). 

When compared to lions' clavicles that of tigers are smaller as well as more straight/not as bended.

*This image is copyright of its original author

*This image is copyright of its original author

Here's the average sizes of the claviculae measured:

*This image is copyright of its original author

Not only was the lion's clavicle a third longer (78.6 mm/58.8 mm=1.3367), it was also broader at midshaft, overall and relatively to maximum length ((6.8 mm/78.6 mm)100=8.65% for lions vs (4.7 mm/58.8 mm)100=7.99% for tigers), at the acromial end (overall; 11.6 mm/10.1 mm=1.1485) and at the sternal end (overall and relative to maximum length; (6.1 mm/78.6 mm)100=7.76% for lions vs (2.7 mm/58.8 mm)100=4.59% for tigers). At sternal end the lion's clavicle was even broader than that of the fossile cats.

*This image is copyright of its original author

Now, the difference is biased by different genders. While almost all the lions were males, all the (known) tigers were female. However, the differences were way too large to be linked only to sexual dimorphism:

*This image is copyright of its original author

Between average sized adult males and average sized adult females the difference in bone size (length, at least) is about 10-15%, depending on the bone. Assuming this, the male tiger's clavicula would, on average, still not be as large and thick as that of the male lion (and it was mentioned that the only female lion's clavicle still belonged to the largest of the sample.) That suggests greater strength in the lion's Pectoralis Major as well as in the deltoid (on fair bone sizes, latter may be rather equal, though) while the tiger has an advantage in flexibility of shoulders. Even if the claviculae of lions and tigers were equally long and equally broad, the lion's muscles still would likely be stronger as it provides a larger surface area due to it being curved meaning higher muscle attachment area. Reply