Size

[tom]

Mar 29, 2020 6:39:48 GMT -5 King Kodiak said:

This is not something we need to have a 20-page argument about. If you want to call an 8-year-old bear a full grown bear - just do it. 
  

Bears can be "adults" but they keep growing. 

Interesting....  Humans must be just like Bears than. I was considered an adult after my 18th birthday and I continue growing as well. ohh ok I thought you meant waist measurement. 

[King Kodiak]

Mar 29, 2020 12:15:10 GMT -5 tom said:

Mar 29, 2020 6:39:48 GMT -5 King Kodiak said:

Bears can be "adults" but they keep growing. 

Interesting....  Humans must be just like Bears than. I was considered an adult after my 18th birthday and I continue growing as well. ohh ok I thought you meant waist measurement. 

Ha ha ha. Same with me Tom, after 18, i kept growing and growing.

[theundertaker45]

I've read through the weight study on Yellowstone grizzlies a second time and noted a few interesting things (I'll attach it below):

Boars:

"In general, males appeared to steadily gain weight annually until at least 15 years of age (Fig. 2)."

It seems that male grizzly bears are considered to be fully grown at 15 years of age, at least in terms of body weight. Calculating the average of the six bears being at least 15 years old, we would come to a mean weight of ~523lbs (237.2kg) and a length (including tip of the tail) of 182.3cm.


"Males reached mean adult size in 7 of the 11 dimensions by 6 years (body length, girth, height at the shoulder, neck circumference, head length, front pad length, and rear pad width) and in all 11 by 9 years."

This means that a grizzly bear has to be considered a mature adult male by the age of nine years, nothing more and nothing less. Calculating the average of the 32 bears being at least 9 years old, we would come to a mean weight of ~470lbs (213kg) and a length (including tip of the tail) of 166.2cm.



Sows:


"Females steadily increased in weight through age 13 (Fig. 2)."

It seems that female grizzly bears are considered to be fully grown at 13 years of age, at least in terms of body weight. Calculating the average of the 14 bears being at least 13 years old, we would come to a mean weight of ~313lbs (141.9kg) and a length (including tip of the tail) of 146.4cm.


"Females attained mean adult size in 5 of the 11 body dimensions by 4 years (contour body length, height at the shoulder, neck circumference, head length, and front pad width) and in all 11 by age 7 years."


This means that a grizzly bear has to be considered a mature adult female by the age of seven years, nothing more and nothing less. Calculating the average of the 48 bears being at least 7 years old, we would come to a mean weight of ~304lbs (138kg) and a length (including tip of the tail) of 152.1cm.


My conclusions are:

- Experienced females and males are heavier than mature adult females and males. It should be taken into account that the difference between adult and experienced males is bigger than the difference between adult and experienced females.
- Females mature at a much faster rate than males.
- When talking about the weight of bears only individuals being at least seven or nine years old respectively can be considered mature adults.


So the stats are the following:

Mature adult Yellowstone grizzly bear (1975-1985): 470lbs and 166.2cm for boars; 304lbs and 152.1cm for sows.


Grizzly Bear Weight data.pdf (343.28 KB)

[King Kodiak]

Yeah, thats the thing with brown bears. Its basically by age class. If you only weight the 15 year olds, you will get a much higher average than if you weight the 9, 10, or 12 year olds. But yeah, for the males, no bear under 9 should be included in the charts to get the average of full grown males. 9 would be the youngest age accepted.

[King Kodiak]

Mature adult Yellowstone grizzly bear (1975-1985): 470lbs 

Did you get this by the 9+ year olds? Because me and brobear got 491 lbs.

[theundertaker45]

King Kodiak

I repeated my calculations three times and I got 470lbs.

[brobear]

Apr 10, 2020 6:56:36 GMT -5 theundertaker45 said:

King Kodiak

I repeated my calculations three times and I got 470lbs.

Some shorter in body length than either lion or tiger; some heavier too.

[King Kodiak]

Apr 10, 2020 6:56:36 GMT -5 theundertaker45 said:

King Kodiak

I repeated my calculations three times and I got 470lbs.

I think you might be doing the math a little different than us, i just did it again:

So we are adding all the 9+ year old bears and then dividing that total weight by the number of lines, which we have 11 lines.



(KG)

1) 199.0
2) 168.9
3) 224.0
4) 199.0
5) 261.1
6) 233.8
7) 301.9
8) 259.9
9) 147.6
10) 215.7
11) 238.4

So, adding all this up we have 2449.3 kg, we then divide by 11 and we get the average weight of 222.66 kg, (490.881 lbs)

[theundertaker45]

I didn't add up the averages and divided them, I added up the number of individuals (32 in this case) and divided them. The reason being that outliners can't influence the actual data to a big extent and the sample size being bigger then.

[King Kodiak]

Apr 10, 2020 7:39:32 GMT -5 theundertaker45 said:

I didn't add up the averages and divided them, I added up the number of individuals (32 in this case) and divided them. 

I see, but 32 divided by what? The correct way is to divide the total weight by the number of lines. 

[theundertaker45]

I'll calculate it here:

199*6=1194
168.9*5=844.5
224*7=1568
199*4=796
261.1*2=522.4
233.8*2=467.6
301.9*1=301.9
259.9*2=519.8
147.6*1=147.6
215.7*1=215.7
238.4*1=238.4

Overall: 6815.9kg, n=32

6815.9/32 = ~213kg (470lbs)

[King Kodiak]

I see what you are doing. You are doing it a little differently. You are actually multiplying some weights by the number of bears weighed for those particular age classes. The thing is the average weight for each age class has already been made, for the 9 year olds, its 199 kg, so that would be just 1 line. Its just 2 different ways of doing it.

[theundertaker45]

You are right but I prefer the second method because of two reasons:

-You get a bigger n (sample size), in this case 32 instead of 11 which makes it more accurate.
-There are a lot of age classes including only one or two individuals which don't give much insight into the average weight for these age classes. That's why the age classes including larger samples (like 9,10 or 11, 12 years old) should have a bigger focus than statistic outliners as we don't know how further individuals would influence the weight classes including only one or two individuals.

[King Kodiak]

You might be right, there are several age classes with only 1 or 2 bears weighted, so those are not really averages, 1 bear is not the average. So anyways, your math had it at 470 lbs, which really is still not bad at all for an inland grizzly population.

[theundertaker45]

An extensive weight study like this one on grizzly bears should be available on all animals, then we would have it a lot easier and there would be much less unnecessary discussion. I remember reading through a similar study involving Kruger lions (although I don't have it available at the moment, that's the name of it: Smuts, G. L.; Robinson, G. A.; Whyte, I. J. (1980). "Comparative growth of wild male and female lions (Panthera leo)". Journal of Zoology)) and they seem to reach their peak weight at the age of eight years (~415-420lbs). Comparing it with the peak weight of Yellowstone grizzlies (~520-525lbs) there is a weight difference of ~95-100lbs in favour of the bear and a length difference of ~5-10cm in favour of the lion.

[King Kodiak]

By the way, the 11 year old weight class had 7 bears weighted, so that is a pretty good amount. They had an average of 224 kg (493 lbs). So that is very high average for inland brown bears.

[OldGreenGrolar]

Brown bears can weigh as little as the barren ground grizzly or as large as a Kodiak bear.

[brobear]

grizzlyencounter.org/grizzly-education-2

Bears of North America: Black Bear (Ursus americanus)

Habitat is most of North America
Colors include black, brown, blond, cinnamon, and rust.
Average weight is 100-350 pounds. In some places up to 700 pounds
Height is 3 feet at shoulders, 6 feet standing.
Rump is higher than front shoulders.
Face profile is straight; muzzle is relatively long.
Ears are long and prominent.
Front claws are less than 2 inches long, curved, and good for climbing. Claw marks do not always show in tracks.

Brown Bear (Ursus arctos (Grizzly & Kodiak bears )

Habitat is Northwestern states, Alaska and Western Canada.
Color varies from blond to black. Often “grizzled” blond on the ends.
Average weight varies: Interior bears 300-500 pounds. Coastal bears 800-1200 pounds.
Height: Interior bears 4 feet at shoulder, 7 feet standing. Coastal bears 5.5 feet at shoulder, 8-11 feet standing.
Ears are round and proportionately small.
Distinctive shoulder hump is mostly muscle.
A dished-n profile between eyes and end of snout.
Front claws are 2-4 inches long. Claw marks are usually visible in tracks.

Polar Bear (Ursus maritimus)

Habitat is Arctic and Sub-Arctic.
Color Varies from bright white to a yellowish or gray tint.
Average weight is 775-1,500 pounds.
Height is 5.5 feet at shoulder, 8-11 feet when standing.
Ears are round and proportionally small.
Distinctive shoulder hump is mostly muscle mass that enables powerful swimming.
Face profile is straight: muzzle and neck are relatively long.
Front claws are 2-3 inches long, curved, and good for hunting seals and climbing on ice.

[OldGreenGrolar]

Reply 271. Sometimes rounding up numbers a bit differently can cause a big difference the result. While I am not an expert in maths, I have tried it in college and got a different answer from my teacher even though I did it the correct way.

[King Kodiak]

Length at age, weight at age, and corpulence indices (CI) for brown bears of northwest Mackenzie, northern Yukon, and northwest Alaska predicted from fitted growth curves







www.researchgate.net/figure/Length-at-age-weight-at-age-and-corpulence-indices-CI-for-brown-bears-of-northwest_tbl1_238012951