Bears of the Pleistocene

[Ghari Sher]

(01-23-2018, 12:20 PM)brotherbear Wrote: Post by brobear on Jan 21, 2018 at 5:20pm
hamzatriestoblog.quora.com/Interesting-new-findings-on-Ice-age-carnivores

Interesting new findings on Ice age carnivores
Hamza Ahmad Shaikh

This is actually a paper from June 2015, and I only hatched the thought to share now, so I should have told you earlier, but alas, here it is.
Unfortunately, only the abstract is available free of charge, but it's still an interesting read (I haven't read the actual paper). It's really challenged some of the preconceptions we've had about ice age carnivores in the Mammoth steppe. Here's the Highlights + Abstract (ctrl+c'd and ctrl+v'd):
Highlights
•Cave bears were virtually all herbivores.
•Giant short-faced bears were consuming meat but not necessarily purely carnivores.
•Scimitar tooth cats were not specialized mammoth predators.
•Most cave lions were focussing on reindeer, especially when competing with other large carnivores.
•Wolves outcompeted cave lions in Europe during Lateglacial.
Abstract

Isotopic tracking of carnivore palaeoecology is a relatively new approach that yielded important results for the study of the non-analogue mammoth steppe biome. After describing the prerequisite to apply this approach and the possible complications, the main achievements will be described for extinct carnivore species such as scimitar-tooth cat Homotherium serum, cave lion Panthera spelaea, giant short-faced bear Arctodus simus, cave bear Ursus spelaeus s.l., as well as for ancient representatives of extant species such as brown bear Ursus arctos and wolf Canis lupus. Isotopic tracking showed that scimitar-tooth cats in Alaska were not specialist proboscidean predators but rather generalist consumers of other large herbivores. The majority of cave lions analysed so far were focused on reindeer, some individuals were specialized on cave bears, especially in contexts of competition with cave hyenas. Giant short-faced bears in Alaska were not pure herbivores and consumed meat from reindeer, muskoxen and possibly other predators, but may have still incorporated plant resources in their menu. In contrast, all cave bear populations studied so far for which a clear dietary reconstruction could be done were virtually pure herbivores, only a few cases are still unclear. Interestingly, brown bears used the opposite extreme of the dietary spectrum when competing with other large bears such as cave bears and giant short-faced bears, i.e. were more carnivorous in Europe and more herbivorous in Alaska. Finally wolves seem to have been outcompeted by hyenas but became dominant predators during the Lateglacial in Europe to the expense of the last cave lions. The results obtained through this approach are also relevant for improving conservation strategies of endangered extant large carnivores.
Paper: Isotopic tracking of large carnivore palaeoecology in the mammoth steppe
I found these findings very interesting, mostly due to my fascination for ice age animals, but also because of how they challenged our previous notions of some of these carnivores.

From the beginning, it was clear to me that the Cave bear wasn't very carnivorous, but I had always figured they had a sizeable amount of meat in their diet, like most modern bears do. It seems that they were actually far more herbivorous than that - to the point where, when their ranges overlapped, the cave bear's close cousin, Ursus arctos, had to exploit a more carnivorous diet in order to avoid competition for plant materials with its larger relative. Known also for its conflict and relationship with Neanderthals (whose validity was brought to my attention by Rolf Kohl, see Cave bear hunting in Hohle Fels Cave in the Ach Valley of the Swabian Jura and Withering Away—25,000 Years of Genetic Decline Preceded Cave Bear Extinction), its reputation as a giant savage ice age bear has been somewhat softened. In fact, this isn't really a carnivore, unlike the others discussed in the paper with their meaty diets. While it was larger and by no means cuddly, I would wager you'd be more likely to be hunted by a brown bear than a cave bear, should you travel to Europe during the ice age.

I don't have much familiarity with the Short-faced bear, but from what I had heard, they were supposedly highly-carnivorous, and were either viscous juggernaut hunters and/or kleptoparasites, scavenging and chasing other predators such as the contemporaneous (but smaller) Smilodon and American lion (see here) off their kills. Indeed, it does appear that their Brown bear neighbours were exhibiting the opposite extreme to those in Europe, but being a bear, one would expect that this beast, however exaggerated by popular multimedia, would have been at least capable of mixed feeding. This also attests to the adaptability of Brown bears to varying conditions, and may help explain why they survived, while other large bears became extinct.

This one struck me the most. Whenever one read of Homotherium, there would be at least some mention of its Mammoth-eating tendencies. Hell, I was even lead to write about this ostensible pachyderm eater's tendencies in Hamza Ahmad Shaikh's answer to What are some fascinating facts about the woolly mammoth?. Indeed, findings from Friesenhahn Cave in North America bore evidence that H. serum, the North American species of scimitar cat, hunted and killed young proboscideans, but given the cat's build, it did appear that these lithe sabretooths weren't ideally equipped mammoth killers.

Mauricio Antón touched on this in one of his blog posts,Homotherium, slayer of giants? on the hunting of mammoths by these cats. He concluded that these cats were either hunting in packs very frequently, or that the Friesenhahn mammoth/ mastodon killings were a local phenomenon, not typical of the entire genus. In the mammoths steppe ecosystem, mammoths were to be found, but in far larger quantities there was other large game that you would expect a lion-sized cat to be hunting. According to Sergey Zimov, "On each square kilometer of pastures lived 1 mammoth, 5 bison, 8 horses, 15 reindeer. Additionally, more rare musk ox, elks, wooly rhinoceros, saiga, snow sheep, and moose were present. Wolves, cave lions and wolverines occupied the landscape as predators. In total, over 10 tons of animals lived on each square kilometer of pasture- hundreds of times higher than modern animal densities in the mossy northern landscape." (see: Sergey Zimov’s Manifesto), leaving plentiful prey for scimitar cats to be exploiting. According to one blog post by someone who did buy and read the paper, the Yak was the preferred prey of scimitar cats:

Then we come to Eurasian cave lions - for some reason or other, my favorite ice age creature. It was already clear to me that they hunted large quantities of Reindeer meat, with cave bears constituting for most of their diet's remainder. My suspicions for the reason this was the case has been reaffirmed, as it appeared that the Cave hyena had a diet comprising of larger quantities of horse and woolly rhino, amongst others (Prey deposits and den sites of the Upper Pleistocene hyena Crocuta crocuta spelaea (Goldfuss, 1823) in horizontal and vertical caves of the Bohemian Karst (Czech Republic)), and that other carnivores had differing diets to avoid competition.

What surprised me about the cave lions is the conclusion that wolves out competed them. I had read beforehand that the cave lion experience a decline in range after the extinction of the cave hyena, but I was unsure why this would be the case, seeing as it was a competitor. It's clear to me now, that the hyena's suppression of the wolf in Europe prevented it from becoming to widespread (though they were huge, see Megafaunal wolf). In the dying days of the late glacial, the cave lion probably struggled to find enough reindeer, and the more generalistic wolf may have been one of the last nails in the coffin for this cat.

Haha!
I'm the author of that blog just to let you know. Didn't realize anyone had quoted that here.
In case you're interested, I wrote a more extensive piece on this after actually accessing and reading the papers (some were available, others.... well, what do you people think of sci-hub?) pertaining to this issue.
https://www.deviantart.com/anonymousllam...-645479135 Reply