Grizzly Bear vs Smilodon Fatalis

[mechafire]

Jan 3, 2015 10:30:54 GMT 5 0ldgrizz said:

With the food resources of Pleistocene North America, there is little doubt in my mind that the grizzly was double the weight of a 450 pound Smilodon fatalis. It is inconceivable that the grizzly would not take full advantage of his resources. The largest big cat of Pleistocene North America was Panthera atrox which averaged roughly 560 pounds. Even he was no match for the much heavier grizzly. The Ussuri brown bear averages roughly 590 pounds and his food resources are poor in comparison to that of the late Ice Age North America.

again, it had to compete with more carnivorous Bears that are more powerful, as well as other large predators (some of which could have lived in groups).

Were predators still alive today, gray wolves, Cougars, etc. larger back then?

[malikc6]

Is there an account of a strong coyote pack killing large prey or enemies like wolves, cougars, or even a bear? (bit of a stretch but who knows?)

[theropod]

Wolves are smaller than bears, that’s true. In much the same way, grizzlies are smaller than Arctodus. Hence why I mentioned their impact on an animal smaller than themselves, which did a lot better when they were not present than now that they are. Pack size could plausibly be analogous to body size, as it determines predatory abilities and food requirements to a good degree.

Neither siberian tigers nor wolves are comparable to short-faced bears in terms of their potential to suppress brown bears, as in the former cases the brown bear is still the larger animal on the block, while in the latter case it is outsized. The presence of a smaller predator that they can displace at carcasses and that is no major predatory thread may be advantageous for bears, the presence of a considerably larger predator an entirely different one. Unless you think pleistocene grizzlies were on par with short faced bears (and prides of large felines of a body size similar to an extant grizzly), and this just happened to be ignored in scientific works, this isn’t the same situation.

If you have no doubt in your mind, you simply aren’t considering it.

[0ldgrizz]

The barren ground grizzlies, among the smallest of brown bears have no trouble competing with the much larger polar bears. During the Pleistocene, I have no doubts that grizzly bears were feeding heavily on animal carcasses. In Siberia, even the Asiatic black bears routinely scavenge on tiger kills. And, if the grizzlies were feeding so, and in the size range of the peninsula grizzlies or Kodiak bears, then there were no big cats in North America that rivaled their size. Also note that even though there are huge brown bears living in the Siberian taiga, their presents does not cause the black bears to feed only on insects and vegetation.    

[theropod]

Whether they were feeding on carcasses or not (they must obviously have done so, albeit whether they did it as much or as successfully as today we can’t say), that is no evidence to claim they were twice their extant size. It should be easy to see how smaller size might also be an advantage for it (in fact, it might precisely have been why it survived). There was such a lot of prey back then, but also the corresponding amount of competition, and unlike today grizzlies were not from the start the largest predators in their ecosystem that could usurp any kill made by other predators.

Assuming for a moment that the grizzly of that time was the same size as today, its chances of defending a carcass wouldn’t be signficantly better than those of a lone Smilodon or American Lion, and obviously well below those of an Arctodus, correct? Can you tell me why exactly grizzlies and not those other animals should have supersized due to the greater amount of food?

[0ldgrizz]

no evidence to claim they were twice their extant size.
I am not claiming that they were twice their extant size; but that they were very likely in the same size range as their living relatives in the coastal regions due to their heavy protein diets. Food availability is the key.  

 

The Grizzly Almanac by Robert H. Busch.

By around 1.3 million years ago, Ursus etruscus had disappeared and Ursus arctos, the brown bear, had evolved, perhaps in the area we now know as China. Grizzlies are a form of brown bear.
Although early bears has strolled over the Bering land bridge between Asia and North America as early as 1.5 million years ago, evolving into the North American black bear, grizzlies did not follow until much later. How much later is a matter of great debate. The earliest fossil brown bears in North America were found in Alaska; these fossils date to 200,000 years ago, although there may have been earlier bears that left no fossil record.
The grizzlies took over the ecological niche formerly occupied by the giant short-faced bear ( Arctodus simus ), which had arrived in North America about 1.3 million years ago. This huge beast was the largest carnivorous land animal ever, standing upright at a height of up to 11 feet. Its snout was short, leading to its nickname of bulldog bear. It had a low forehead, long legs, and weighed almost a ton, making the bulldog bear a powerful predator.
The giant short-faced bear and its cousins finally became extinct in the mid- Pleistocene Period. The most likely reason for their demise is increasing competition from the brown bears, which spread rapidly across the continent.

[theropod]

As was already discussed an extant grizzly should be quite similar to Smilodon in size (if you think it isn’t, that would surely be a more rewarding subject of discussion tough), you claimed the pleistocene one was twice the size. This topic refers to Ursus arctos horribilis, doesn’t it? Had someone wanted a Kamchatka brown bear or a Kodiak bear, that would have been specified.
btw that quote claims the short faced bear to be the largest carnivorous land animal ever?

This huge beast was the largest carnivorous land animal ever, standing upright at a height of up to 11 feet.

[0ldgrizz]

There is only one species of brown bear; Ursus arctos. The Ussuri brown bear ( mature male ) averages roughly 590 pounds; 140 pounds heavier than Smilodon fatalis. And Siberia is not a land of rich food availability. The Pleistocene grizzly without a doubt ate better than the black grizzly of Siberia. The American inland grizzly lives in poor harsh environments. When they were heavily populated over the western half of the lower 48, there were indeed some large bears. Even today, some of those inland grizzlies weigh from 800 to 900 pounds. Those are individuals who discover rich food resources.

[Godzillasaurus]

Smilodon has significantly better weaponry, albeit a potentially inferior bite force (to a large margin).

[0ldgrizz]

I believe that bite force is often overrated. Yes, the saber-toothed cat has very impressive weapons. However, if my theory holds true, the Pleistocene grizzly was likely about double the weight of the big cat.

[mechafire]

Jan 4, 2015 5:37:13 GMT 5 0ldgrizz said:

I believe that bite force is often overrated. Yes, the saber-toothed cat has very impressive weapons. However, if my theory holds true, the Pleistocene grizzly was likely about double the weight of the big cat.

do you think other modern predators still alive would have been larger? Were cougars, gray wolves, Jaguars, etc. supersized?

[0ldgrizz]

Jan 4, 2015 6:17:11 GMT 5 mechafire said:

Jan 4, 2015 5:37:13 GMT 5 0ldgrizz said:

I believe that bite force is often overrated. Yes, the saber-toothed cat has very impressive weapons. However, if my theory holds true, the Pleistocene grizzly was likely about double the weight of the big cat.

do you think other modern predators still alive would have been larger? Were cougars, gray wolves, Jaguars, etc. supersized?

The prey and feeding habits of cougars and wolves were likely no different than today. But, when meat is available, a grizzly will eat meat. Yellowstone grizzly bears eat some meat, but they sometimes feed heavily on pine nuts and even moths; whatever is available. The only reason that the grizzlies of the Alaskan peninsula are larger is the salmon. Also, the size range of brown bears is far greater than among various populations of cougars or wolves. The barren ground grizzly of the arctic tundra average in the 300 pound range while Kodiaks generally weigh a thousand pounds or better. It all has to do with food availability. In Pleistocene North America there was no shortage of meat. There is no possibility that a grizzly would smell the kills of wolves and big cats and not investigate. Those bears without a doubt fed heavily on protein-rich meat.

[creature386]

Jan 4, 2015 6:42:16 GMT 5 0ldgrizz said:

But, when meat is available, a grizzly will eat meat.

Not necessarily:

Even in ecosystems with abundant meat resources, green vegetation can be an important seasonal food resource.

link.springer.com/article/10.1007/s004420100637

Jan 4, 2015 6:42:16 GMT 5 0ldgrizz said:

In Pleistocene North America there was no shortage of meat. There is no possibility that a grizzly would smell the kills of wolves and big cats and not investigate. Those bears without a doubt fed heavily on protein-rich meat.

The problem is that there were not only many other predators (as the others pointed out), but also kleptoparasites to compete with, such as Arctodus. Arctodus, with its greater size and greater focus on meat than a grizzly, would have been a tough competitor that could have restricted the size of the grizzly. It is hard to tell if there was enough place for both.

[0ldgrizz]

The grizzly will certainly supplement his diet with such things as vegetation and brood insects. However, with such a rich supply of meat, and with the grizzly's super-keen sense of smell, there is no way he is going to munch on grass and honeysuckle while the aroma of a carcass is calling to him. I would bet that there were very few days that a healthy grizzly went without a feast on a carcass.
In Siberia, the Asiatic black bear routinely scavenges on tiger kills, regardless of the danger of both the tiger and the grizzly. Above the arctic circle, the barren ground grizzly scavenges on beached whales and will even displace any but a mature male polar bear; chasing off bears bigger than themselves.
Because the true habits of the short-faced bear cannot be observed and studied, we think of him as a killing-machine. Maybe he was highly aggressive, and maybe not. However, from reading of the historical grizzly from such sources as Lewis and Clark, we do know for certain that, until the invention of the breech-load rifle in 1848, the grizzly was a seriously aggressive bear. His aggressive nature was born during the Pleistocene.

[Vodmeister]

Jan 4, 2015 23:39:20 GMT 5 0ldgrizz said:

In Siberia, the Asiatic black bear routinely scavenges on tiger kills, regardless of the danger of both the tiger and the grizzly.

With "routinely", you mean "very rarely", right?

And with "tiger", you mean small females and juvenile tigers, right?

Because both sloth bears and moon bears are absolutely dominated by Bengal tigers in their natural habitat. Bengal tigers control and suppress smaller bear populations in their area.