‘Sparta’ – the best preserved ice age animal | Polarjournal
The bodies of the two mummified young cave lions Boris and Sparta are very well preserved. a) The female Sparta; b) the male Boris; the heads of the two cubs from the side: (c) Sparta; (d) Boris; e) Sparta from above; (f) dark brown tail tip of Sparta. Photos: Boeskorov et al. 2021

In 2017 and 2018, a licensed collector of mammoth tusks found two mummified cave lion cubs in the thawing permafrost of Yakutia. Initial analysis revealed that the two cubs, found only 15 meters apart, were not siblings. The age determination by radiocarbon method revealed that ‘Boris’ lived nearly 44,000 years ago and ‘Sparta’ about 28,000 years ago (we reported). Scientists from various international institutions examined the finds more closely in the past few years and published their results and new image material a few days ago in the special issue “Advances in Quaternary Studies: The Contribution of Mammalian Fossil Record II” of the journal Quarternary.

In Yakutia, more precisely in the Indigirka River basin, many bones and several mummified animals from the Pleistocene have already been found. A variety of large mammals once populated the mammoth steppe: in addition to cave lions (Panthera spelaea), wolf, brown bear, wolverine, woolly mammoth, woolly rhinoceros, saiga antelope, reindeer, Lena horse (Equus lenensis) and steppe bison lived in the vast plains.
So far there have been four finds of cave lion cubs, all from the Indigirka area, and ‘Sparta’ is “arguably the best-preserved Ice Age animal ever found”, according to the Centre for Palaeogenetics in Stockholm.

The Republic of Yakutia (also known as Sakha) is located in northeastern Russia. A total of four mummies of young cave lions have been found in the Indigirka River basin, two on the Uyandina River in 2015 (red triangle) and two on the Semyuelyakh River further east (red star). Map: Boeskorov et al. 2021

The international research team, consisting of scientists from Russia, France, Sweden, Great Britain and Japan, examined the two cave lions using computed tomography, among other methods. Using the CT images, the researchers were able to determine the skeletal shape and condition of the soft tissues, as well as create 3D models of Boris and Sparta. The stage of development of the teeth indicates both were one to two months old at the time of their deaths. However, the teeth do not correlate with the small head and body size, suggesting faster postnatal development than in modern lion cubs, according to the scientists. It is possible that the shorter summers and harsher winters necessitated faster growth and an early switch to a meat diet.

The tomographic image of Sparta shows that the skin and bones are intact with no injuries from predators. Image: Boeskorov et al. 2021

The scientists could not see injuries from predators or scavengers on the CT images, so they assume that Boris and Sparta died in their caves under the snow or in the earth. They could have been buried in their dens during a landslide and their bodies may have been deformed by the weight of the earth and the permafrost. In any case, the small bodies froze very quickly after their death, which is why they were so well preserved until they were found.

The CT images also confirmed, in combination with molecular sexing, that Boris was a male and Sparta was a female, which was also initially thought to be a male and named ‘Spartak’.

Uterus-like organ structures can be seen on the CT image of Sparta (green arrow). Image: Boeskorov et al. 2021

Studies of the fur revealed that cave lions, unlike modern African lions, had thicker undercoat evenly distributed over their bodies, which likely helped cave lion cubs adapt to the cold climate, the researchers said. Boris and Sparta have quite similar characteristics in terms of hair length and undercoat, but their coat colors differ. Although both were about the same age, Sparta’s fur has more reddish and brown shades than Boris’, whose fur is lighter and yellowish gray. In their study, the researchers hypothesize that female juveniles retained the darker juvenile coat color over a longer period of time, although it is just as possible that the different color came about after the fact due to the long time spent in the frozen ground.

CT scan of Boris shows testicle-like organs. Image: Boeskorov et al. 2021

Aside from the larger body and denser fur, the cave lions of that time and the African lions of today are very similar in appearance. However, an iconic feature of African lions, the male’s mane, appears to be absent in cave lions. Early cave paintings depicting cave lions, in which a mane is very rarely indicated, underscore this assumption. The absence of a mane could mean that cave lions, unlike their African relatives, did not live in hierarchical social structures, but rather as solitary animals. Currently, scientists are still arguing about whether cave lions roamed the mammoth steppe in prides or alone.

Julia Hager, PolarJournal

Link to the study: https://www.mdpi.com/2571-550X/4/3/24/htm#

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