Bears of the Pleistocene

[tigerluver]

Here's a whole chunk of new bear reading.

Some more fossils. 

*This image is copyright of its original author

*This image is copyright of its original author

The records are hard to analyze. A lot of the fossil material references in the attached paper I can't find, probably because there from late last century, and not digitized yet. The Harington et al. (2014) specimen looks to be around 240 kg. The skull fragment doesn't seem to add up to a large anima on the other hand, but I am not sure.
 
Then we have measurement-less quotes like these:
"The complete skeleton from El Capitan Cave, as well as portions of several others, were of black bears,
distinguished from the living bears on the island only by their large size. Their size seemed especially significant
since they appeared to be females based on the lack of bacula and the gracile structure of their skulls. Even more
significant was the discovery of even larger bear remains that we identified as brown bear. (Harington et al. 2014)"

What exactly is large®/giant size? Unfortunately, for now, this is the best idea of the relative size of the Pleistocene brown bear form. It is still a real possibility than brown bears underwent a size increase after the competition died out.

Also, it seems Matheus (1995) went over the mammoth carcass scenario as well in a way: 
"If short-faced bears were large, aggressive scavengers capable of stealing carcasses from other large carnivores, then it seems unlikely that brown bears could dominate them in direct interference competition. And while brown bears may have preferred to feed on animal carcasses, it seems more likely that they would have avoided direct confrontation with a dominant bear. Instead, brown bears would have been doing what they do best - making use of a variety of dietary resources and habitats."

I admit, the giant size of some Pleistocene species really is fascinating. But that's a double-edged sword... 

"The ecological plasticity of brown bears and their ability to hibernate may have been the keys to their ultimate survival at the end of the Pleistocene, while Arctodus, the highly specialized forager, was not able to find a niche in Holocene ecosystems. Most likely, carcass densities on Holocene landscapes fell below levels necessary to sustain minimal viable populations of short-faced bears. Since many bears hibernate to survive poor food availability during winter, this may be an indirect indication that short-faced bears, and perhaps all New World bears, never evolved this strategy to survive seasonal dietary bottlenecks.(Matheus 1995)"

 

 

 

 

 

 

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