There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
While I too noticed that Panthera leo usually has slightly longer and wider bones than Panthera tigris, I do not agree on the statement that bone density is higher in the latter then in the former. It is also not clear what it is meant by bone density. Generally density of bones are compared from the ratio of their wet mass to their wet volume measured while fully submerged in water for at least 15 minutes. Bone density can also be ascertained by their mechanical properties and by the bone mineral composition. In a study I did long time ago on skeletal properties of carnivore limb long bones, I concluded that Panthera leo appears to have slightly higher either cortical area and principal moments of inertia then Panthera tigris. This is compatible with the higher bone stresses occurring in fast locomotion of a more cursorial species. Therefore lion bones appear to likely be more then just slightly more robust as the higher external robustness in all compartments (proximal and distal epiphysis and diaphysis) is also corroborated internally.
An investigation performed in the past also revealed the ratio of the skeletal mass to total body mass computed for an adult captive female lion in excellent condition to be around 12,5 %. The ratio between musculature and total lean body mass (bones and muscles), the way it is normally computed, for the aforementioned female lion was 62.5% (59.2% if computed on total mass including fat) This value is higher then in any other mammal species on which I am aware of all the dissection details and how it has been calculated, but among these species Panthera tigris is not included. I would also expect the value higher for a wild specimen in comparable excellent physical condition. A sub-adult captive male lion evaluated as rachitic and below average size has been measured having a muscle mass percentage of 55.0% after dissection, still a value higher then the one of very most mammals. Typical range of musculature over total body mass in felids is 56-59 % and in mammals 44-50 %. Therefore Panthera leo lies very much in the upper end of felid range.
I already reported in my previous post just issued on a different thread (today I am unusually productive for the Forum) that in one of my past studies I computed the lumbar vertebral column section to the presacral vertebral column length in Panthera tigris to be 33,8% on average. I computed that same ratio in Panthera leo at 32,7%. Cervical area of tigers is also proportionally slightly shorter then in lions on average (ca. 25.5 % vs 25.9%). The thoracic section averages longer in Panthera leo then in Panthera tigris (less then 41,4 % vs 40,7 %). I computed an average scapula ratio to the presacral vertebral column in Panthera leo at 24,42 % and 23,25 % in Panthera tigris, but the grestest length of processus articularis appears to be slightly longer in the tiger then in the lion (24,7 % vs 23,6 %). The brachial index in lions is higher then in tigers while the crural index is pretty much the same. Tigers appear to have proportionally longer hind limbs to fore limbs then lions. The relative length of the oleocranon process in Panthera leo is longer implying higher leverage for the triceps. The front paw is proportionally wider in the tiger, but because the lion on average has longer metacarpals (and metatarsals) in absolute terms. I can carry very much on highlighting skeletal differences, although always marginal or very marginal, but I stop here.
We also know Indian and Amur tigers to have slightly longer head-and-body length and slightly shorter skull then lions while the latter are slightly taller at the shoulder on average (not only proportionally). Chest girth appears larger in Panthera tigris tigris but accounting for Ngorongoro Crater adult male lions estimated at 212 kg on average based on chest girth, reversing my formula (a thoroughly computed one) it would imply an average chest girth of nearly 1300 mm on live animals after expiration (as normally measured) and therefore pretty much as the highest Indian tiger averages computed from hunting records (all animals obviously dead and therefore at least some possibly affected by post-mortem inflation). Forequarters (particularly the distal elements) and hindquarters of big male tigers generally appears stockier then those of most big male lions. Chest of female lions generally appears proportionally wider then chest of female tigers in pictures and circumference of the largest and bigger lion population seems to cautiously confirm this feeling.
I believe modern Indian tigers are slightly bigger on average then modern African lions because of a combination of different elements including prey size, density and typology, habitat characteristics, sociality, and interspecies and intraspecies competitions. The difference in average body mass is marginal and in my opinion around the rounded figure of 10 % (it can also be 5 %, 12 % or 15 % I do not much care as it depends from which data one includes) or so comparing either the populations as a whole or the largest / heaviest ones for each (for instance northern India and Nepal tigers with Ngorongoro Crater lions). It is just because the difference is so marginal, debatable and manipulable that size of lions and tigers has been vigorously discussed and will still heatedly be discussed for ages with little or no chances to find a common and peaceful agreement. Also because for any reliable actual weight of a very big tiger thrown in the scene, one can always find a similarly reliable weight of a lion individual comparable to the former. The story will likely never ends.
