AnonymousLlama428

NOTE: I am NOT an expert in any field, these are my own findings based on my own readings.

Sexual dimorphism is quite high among the pantherines, no doubt, and the cave lion is no exception. Indeed, it was once argued by some authors that two distinct races of lion, one large and one small, inhabited Europe during the Pleistocene, until it was shown that the morphological and size differences seen between these two apparent races fit comfortably into the known osteological and dental sex differences observed in extant lions, and was shown by Turner (1985), who concluded that they were at least as sexually dimorphic as modern lions[1].

However the statement that cave lions were more dimorphic than African lions, and the aformentioned figures, seems to have originated from Baryshnikov & Boeskorov (2001)[2]. Using mass equations developed by Jefferson (1992) using tooth measurements, they calculated the mean body mass of the Eastern cave lion (the population east of the Urals, aka. Panthera spelaea cf.vereshchagini, though this distinction is unsupported by genetic evidence) being 194kg for males, and 154kg for females - big, but actually approximately the same mean mass as the Southern African lion populations[3]. The cave lions living west of the Urals (Panthera spelaea cf. spelaea) on the other hand, grew much bigger - the smaller size for the eastern lions is largely attributed to the harsher environment[1]. The percentage difference in mass calculated for these lions ((1-(female weight/male weight))x100) is 21%, this contrasts with the apparent 15% of Modern African lions. Apparently, according to Understanding the Late Pleistocene: Cave LionThe Cave Lion
(Panthera spelaea spelaea)
Taxonomy and Relationships:

Cave lions, also known as Northern or steppe lions, lie within the big cat genus of Panthera along with the extinct American lions (P. atrox) and also lions (P. leo), leopards (P. pardus), snow leopards (P. uncia), jaguars (P. onca), and tigers (P. tigris). They’re now usually agreed to be a separate species than lions, being classified as Panthera spelaea, based on both considerable morphological and phylogenetic studies. Lions remain the cave lion’s closest living relative nonetheless. [1]
The early to middle Pleistocene Panthera spelaea fossilis is the direct ancestor of the cave lion which evolved in Eurasia about 700,000 years ago. The climate it lived in was warmer than that of the later cave lion and it was larger. [2] Its status as subspecies instead of a full species (P. fossilis) is deb the dimorphism for the western cave lion population was even higher, at 31%, but I can find no mention of this in the literature.

I see a few problems here.

Firstly, my understanding of mass estimates is that using tooth measurements is not the most reliable way of estimating the body mass of an extinct mammal - using regression equations incorporating longbone data seems to be more reliable, since they are directly responsible for supporting the animal's weight, and thereby there is a closer relationship between longbone biometrics and body mass. However, in Russia, complete cave lion remains are quite scant, so it is understandable that this may not be possible for the Eastern cave lion population. In any case, the proportions of cave lions were fairly similar to those of modern ones[4], so the mass estimates based on equations that presumably used lion teeth shouldn't be too far off. For the sake of this journal I'll assume they're fairly veridical.

Secondly, Baryshnikov & Boeskorov (2001), as well as later authors such as Sabol (2018)[4], both cite George Schaller's 1972 book The Serengeti Lion[5] as a reference for this 15% figure for African lion dimorphism. Looking through it, I find no mention of this 15% figure, but perhaps this was calculated from some of the mean lion masses given by him.

I have tried to do some calculations on this myself in order to verify this. With the exception of a sample of Kenyan lions (5 lionesses, 14 males) from a previous paper referenced which gave a mean of 151kg for lionesses and 172kg for males, yielding a low 12.2% size disparity, the two other times in the book where figures for mean sex-specific lion mass (or ranges given whence the mean was calculable) gave size disparities of 26.7% and 29.4% between the sexes (mean 22.8%, but 28.05% excluding the 12.2% outlier). This is much higher than the supposed 15% and 21% purported for African and cave lions respectively.

Incorporating data from Schaller (1972) and other literature on mean lion mass, I found a very interesting consistency in sexual dimorphism:

I calculated disparities of 25.8-33.8% (mean 30.55%) for differing samples across Africa using the data from Smuts (1980). Combining Schaller (1972) with Smuts (1980)'s datase I get an overall mean of a 29.7% disparity.

The outlier of 12.2% seems to be attributable to the smaller and thereby more biased sample size of lionesses (n=5), where as a more representative sample of males (n=14) was used[5].

But how does this compare to the cave lion?

While this is larger than the 21% figure for cave lions, and used dental measurements, so it may not be as accurate as it could be, and this figure was calculated for the eastern population only, dimorphism may have differed to some extent in the larger western cave lions,.

So this brings on another question........

As said before, limb bones are ostensibly more reliable predictors of an animal's mass, and hence I looked through the literature for felid mass equations pertaining to longbone biometrics.

I used the equations that Christiansen & Harris (2005)[6] used to calculate the mass of Smilodon, and the felid variation of the mass equations in Christiansen (1999)[7], though I must say that as far as my knowledge goes, the former is more reliable.

While in Russia, which comprises the lion's share of the eastern cave lion's range, cave lion remains are often fragmentary (only one reasonably complete skeleton has ever been found), the same is not true for the western population; due to the cave-rich regions which they inhabited, accompanied with their predation behaviours on cave bears, attempts at kleptoparasitism on cave hyenas, and importing of their remains by hyenas into caves, we have a much larger sample of cave lion limb bones available.

After calculating the mean longbone biometrics (length, distal width etc.) I got overall weights of 224.87kg for male lions, and 164kg for lionesses using Christiansen & Harris (2005)'s equations and 230.69kg for male lions and 181.12kg for lionesses using Christiansen (1999)'s equations. This gives a size disparity of 27% and 23% respectively, and a mean of about 25% is we average out the masses obtained from the different equations - though, AFAIK, the 2005 study's equations seem to be more reliable.

In any case, the levels of dimorphism from 23-27% seen don't seem too far off from the apparent 21% of the eastern population, and seem to fall within, or just under the levels of sexual dimorphism seen in the African lions (25.8-33.8%).

So it seems that sexual dimorphism in the cave lion was similar to that seen in the African lion, and potentially varied across its range, though some of this may be attributable to imprecise calculations, but hey,

[1] www.sekj.org/PDF/anzf21/anzf21…

[2] www.zin.ru/Labs/theriology/sta…

[3] zslpublications.onlinelibrary.…

[4] www.tandfonline.com/doi/abs/10…

[5] drive.google.com/file/d/126kBH…

[6] app.box.com/s/3aksba3fczggnppb…

[7] www.sekj.org/PDF/anzf36/anzf36…