Home Forums Hunting & Shooting Hunter's Campfire 712 LB Yellowstone Grizz

The 19-year-old male was well known to biologists in Yellowstone National Park, where the big bear resides. As a 3-year-old in 2007, he weighed in at 232 pounds. During a 2010 handling, the boar had plumped up to 393 pounds. His weight stayed in that range, registering at 381 pounds when caught and immobilized at age 9 in 2013.

Then a decade went by without Grizzly 566 coming onto biologists’ radar.

Yellowstone biologists nabbed him once more on Oct. 15 while trapping bruins for routine grizzly bear monitoring, according to Interagency Grizzly Bear Study Team leader Frank van Manen. It was the tail end of a verdant summer following a long-lasting winter in the Northern Rockies. Grizzlies in the Yellowstone region eat upwards of 266 species in four animal kingdoms, and options for foraging were evidently plentiful in 2023 — and especially so for this bruin.

Grizzly 566 weighed a whopping 712 pounds.

“You don’t come across animals of this size very often,” van Manen said.

In fact, he said, the only heavier Yellowstone-region grizzly bear ever documented was encountered all the way back in 1977. That beast of a bruin was a 715-pound male.

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In some respects, Grizzly 566’s near record-breaking heft isn’t completely surprising. Male grizzly bears don’t reach their peak body size until age 14, van Manen pointed out.

Plus, a couple other grizzlies handled in 2023 had relatively high body fat percentages, he said. Ordinarily, by October, females reach 28% to 30% body fat and males are just a little bit fatter — it’s 32% or so of their fall body mass.

Boars are the fatter sex because they need extra reserves for when they emerge from the den. That’s breeding season: Males are more interested in getting to know female grizzlies than extensive eating, and they’re actually losing “quite a bit” of body mass in April and May, van Manen said.

Grizzly 566 figures to be set up well for ursine philandering come next spring.

“He had 41% body fat,” van Manen said. “It looks like the highest [body fat figure] we’ve had before was 43%.”

Were Yellowstone-region grizzlies as a population fatter than average in 2023?

Tough to say, van Manen said, though the rate of fat gain appeared “pretty much normal” this year, he said. The leanest time of year is the end of June, when grizzlies typically range from 15% to 20% body fat. Because dozens of grizzlies are captured across the ecosystem throughout each spring, summer and fall, comparing grizzly bear fat levels from one year to the next isn’t straightforward statistically.

Taking a longer view, however, the science on grizzly bear body fat is more clear. Grizzly fat accumulation rates have not changed over the decades, nor is there any correlation to population density, recent research has found.

That says a lot, van Manen said, about the remarkable plasticity of grizzly diets: Even as major food sources like whitebark pine, cutthroat trout and some ungulate populations have declined, bears are still packing it on.

“The way these animals are gaining fat from June through October hasn’t changed,” he said. “These are incredibly resourceful animals and they’re finding calories on the landscape.”

Fat bastard for a soy boy.

The GF was reading a partial article from the Billings gazette I believe (had to subscribe for the full article…) it said something about a grizzly sighting in the Missouri Breaks. They’re slowly moving east.

This Yellowstone porker walked right past my vehicle a few years back.
Nearly could have touched him.

Big ass bears!

Never seen a grizz in the wild. Only black bears, and have seen quite a few of those.

They are seeing them well east of the Pryor mountains as well.
Give it ten years and they will be out to Miles Ciity.

Osky

I think once they get back on the plains and away from the exercise of mountain living you will see them much larger. Some black bears in MN have topped well over 800lbs, those grizzlies should have no problem getting beyond that.

just listened to a podcast about GNP's Night of Grizzly in '67

interesting perspective on attitudes toward Grizzlies up until then.

glad I didn't listen to it before I went hiking up there

Would not surprise me if this was the same bear.
He was huge.

I've looked at a lot of Grizzlies.

I thought it was pretty routine for Grizzly Bears to get this big. Really tells how much I know about the species.

Coastal fish eating bears, yes. "Interior" bears, no so much.

There were at least 4 different grizzlies on an elk carcass that we found fall 2022. We set up a trail camera and caught these bears. At least one was as big as the Yellowstone bear in the article…









Will

There was an 880 lb. Black bear shot in North Carolina in 1998. This Grizz is a pipsqueak in comparison.

That Black Bear fed on Soybeans, Corn besides whatever it scrounges in the woods.

Duh! Yellowstone grizzlies supplement their meager diet with hikers from Minnesota & Michigan.

If the link works here is the 830 pound Lincoln, MT grizzly road killed a few years ago. https://crownofthecontinent.net/ent...ana/ea4d811b-408f-480c-9f2b-a12a644efca4

The difference is attitude.
Grizz ain't like black bears at all.

Like Mike Tyson fighting Jerry Garcia.

Great pics you guys. Magnificent animals. Thanks for posting.

How heavy can the coastal fish eating bears get?

General Description

Brown and grizzly bears are classified as the same species even though there are notable differences between them.


Fast Facts

Size
Up to 1,500 lbs
Distribution
Brown bears occur throughout Alaska except on islands south of Frederick Sound in southeast Alaska, west of Unimak in the Aleutian Chain, and Bering Sea islands.
Diet
Onmivorous
Predators
Other Brown bears
Reproduction
Twins are most common, but litter sizes can range from 1 to 4
Remarks
Can be a wide range of colors
Other names
Brown and grizzly are both used in Alaska

https://www.adfg.alaska.gov/index.cfm?adfg=brownbear.main