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.
02-11-2015, 02:10 PM( This post was last modified: 02-11-2015, 07:25 PM by WaveRiders )
1)
The bone density testing that you are referring is a bone mineral density test (BMD). The mineral composition of a bone obviously affects its strength, but it is the way the bone material is distributed macroscopically that makes the difference in the mechanical properties unless the animal suffers of osteoporosis or other bone sickness. The size, shape and proportion of the bone section to its length dominate the overall mechanical properties of a bone. One parameter easy to evaluate is how a bone is heavy relative to its volume (macroscopic density) and this is done in the way I highlighted, meaning measuring its wet mass and wet volume.
2)
I specifically referred to captive lions only in the study concerning the ratio of the skeletal mass to body mass and in the ratio of muscle mass to lean/total body mass The animals were a captive adult female lion in excellent condition and a rachitic subadult male lion.
Most of the qualitative and quantitative data/info I released refer to wild lions and wild tigers otherwise, consistently for both species, to wild/captive lions and wild/captive tigers.
The majority of the qualitative info I highlighted has been investigated to a different extent, even quite deeply, by many published studies other then my study and they all substantially suggest very similar and rather consistent conclusions which is also mine.
The data on the ratio of the vertebral column section and scapula length to the presacral vertebral column length and the ratio of the greatest length of processus articularis to the scapula length are unpublished data from my study. In this case I also used captive lions and captive tigers to increase the sample size of both species. I am not comparing cranial and dental characters where it is well known for over a century the significant effect of captivity and that therefore only wild specimens must be used. There are going to be effects of captivity on postcranial skeletal formation and characters too, but I used the same proportion of wild and captive individuals for both species. Using wild specimens only for both species the conclusions do not appear to change as the trends seem to be confirmed, but it is clear that it would be better to investigate the matter using more individuals for both species. The problem is that there are few data available of definite wild individuals and few complete skeleton of wild individuals available for measurements from Museums and other Institutions unless travelling all around the world to find and measure as many as possible. The process to study and measure a complete skeleton is long, complex delicate as you can imagine.
In any case bear in mind that it is always a close call between tigers and lions cranial and postcranial parameter comparisons.
As a further note I highlight that the tiger may have an overall edge in the distal forelimb elements radius and ulna. It is a very close call with some parameters suggesting more robustness in the tiger others in the lion. The relative length of the oleocranon process to the ulna length may actually be longer in Panthera tigris then in Panthera leo. Overall I would suggest the tiger has a slight edge in robustness of the radius/ulna compartment as well as in the solidity of the front paw (proportionally longer in the lion). As I wrote before instead basically all robustness parameters of humerus, femur and tibia from external dimensions and cortical area appear higher in the lion then in the tiger.
In terms of heart mass to total body mass and lung mass to total body mass ratios data from published studies appear to suggest the lion has an edge over the tiger. These trends and the higher overall relative robustness of the limb long bones of the lion compared to those of the tigers (with likely exception of the radius and ulna) appear to me consistent, as I wrote before, with the higher endurance demands and the higher bone stresses occurring in fast locomotion of a more cursorial species like the lion is compared to the tiger.
3)
If you meant that what at the end makes an average Indian/Nepal tiger somewhat heavier then an average African lion is primarily a slightly longer body length (exacerbated by the slightly longer skull in the lion) is a fair conclusion. This is however the final effect. I instead highlighted what could have caused the evolution to follow this direction. Bear also in mind that Indian/Nepal tigers appear more sexually dimorphic then African lions and that sexual dimorphism in tigers is highest in the two largest forms (Indian sub-continent on one side and Manchuria, Amur-Ussuri region on the other side).
I believe the convergence at a particular average body size for both species is also partly due to the evolutionary pressure coming from their polygynous mating system which is the same among the Felids but emphasized from being applied to the two largest species as well as the two apex predators of their respective ecosystem (the brown bear is not a pure predator). However the social system of lions and tigers is different and there are an evident sexual character difference of the male lion compared to the female lion (the mane perhaps limiting or not requesting a too high sexual dimorphism for a social carnivore living in open woodlands and savannah). As highlighted in my previous post there are also different evolutionary pressure from the preferred habitat characteristics, the large prey size that tigers are able to consistently hunt alone, prey density and typology, and from the extent of interspecies and intraspecies competition in relationships to the social system. Most of the African open woodlands and savannah is a significant tougher habitat then the Indian jungle. Lions are social carnivores (to a different extent among population depending from density and other general parameters) because that is the way they can increase individual success and because they can better compete against clans of spotted hyenas and packs of wild dogs in areas where the density of these animals is high. African lions could have evolved becoming much bigger, as it occurred, likely for different reasons too, in Eurasia and North America during the Middle and Upper Pleistocene, but increasing body size has a cost and the African/Asian lion could not afford it.
4)
Without recurring to my data, just check the average and maximum chest girth of Indian/Nepal tiger females from historical and recent data and compare those figures to average and maximum provided by Smuts et al. (1980) for Rhodesia and Kalahari female lions 4 years old and older and the maximum for Kruger NP female lions 4 years old and older. It appears that those female lions has a clear edge over Indian female tigers exceeding possible sample bias.
