The right bank of the Aldan is also where the northernmost sighting of a tiger in the 19th century happened.
I guess these datas are all for Late Pleistocene. Here's the source for more clear informations.
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>makes sense that as the climate warmed and trees took over, mammoths and rhinos would go extinct
During interglacial periods, mammoth steppe tend always step back, but it never disappear (mamoth steppe exist even now, but without ungulate grazing is slowly deteriorating). So climate warming can explain mammoth/rhino/bison reduction, but can't explain their disappearence.
Also, reindeers, muskox and horses were less grass reliant, but they all lived in the mammoth steppe, they didn't lived strictly in forests.
But are they introduced? Northern Kenya seems to be consistently colored in range maps of either dromedaries or their wild ancestor (Camelus thomasi), such as this: https://www.semanticscholar.org/paper/Prospects-for-rewilding-with-camelids-Root-Bernstein-Svenning/26e4523eb2b6346327f7c8b31fe8baa660bda446
In any case, lions and camels have a long evolutionary history together with the lion as a natural predator of the camel, so it's nice to see them getting back at it despite the best human efforts to tear them apart.
I think is something that any climbing felid could/would do when stressed by other predators.
Eurasian lynx sometimes put their prey on trees to protect them from bears or wolves for example
I highly recommend Forgotten Grasslands Of The South. A fantastic book if you are interested in megafauna and grassland ecosystems.