Sunday, March 28, 2010

Week 13: Grizzlies

Distribution Source:
Content Source: Exhibition Wild
Format: Video
Length: 45 minutes, 57 seconds
Link: 800 Pound Best Friend

Earlier today I came across the story of Casey Anderson, a man who apparently is "best friends" with a grizzly bear. The two spend time with each other daily, and the bear - perhaps ominously named Brutus - was Casey's best man and attended his recent wedding (you can find the wedding picture here). Brutus stands 7 ft. 8 in. and weighs over 800 pounds - and is still only an adolescent. This alone seemed ridiculous enough to merit further research.

I quickly confirmed that Casey was not the same person as Timothy Treadwell, the ill-fated "Grizzly Man" notorious for approaching and even touching wild bears in their native habitat. Unfortunately, he and his girlfriend were mauled to death and partially eaten by at least one grizzly in Alaska in 2003. So given this gory tragedy, why would Casey - a naturalist trained to know and understand the serious risks posed by grizzlies - befriend what I consider to be one of the most awe-inspiring and terrifying animals on the planet?

The story begins with young bearcub Brutus, who was born on an overpopulated wildlife preserve. He was therefore likely to be euthanized - there simply wasn't enough room for more grizzlies. So Casey saved Brutus by creating a bear sanctuary in Montana, and has raised him ever since. As Casey describes it, the difference between his story and Timothy's is simple: he would never come close to wild grizzlies. Brutus has grown up with Casey and recognizes him as his keeper and source of food. The cool part about having a large, well-trained grizzly bear (he can even give high fives) is that Casey can measure things like strength, speed and agility without having to risk an encounter with a wild grizzly. (He stays at least 100 yards away when tracking wild grizzlies.) In my opinion it is still outrageous to continually put yourself in such close contact with a grizzly bear, albeit a domesticated one. He is, however, using Brutus to educate people about grizzlies and more broadly about the impact of humans on the natural habitats of wildlife.

One look at the statistics on these animals is enough to send you running in the opposite direction... Not that you'd get away - grizzlies can in three strides reach a speed of 40 mph, equal to the speed of a race horse. Their sense of smell is seven times stronger than that of a bloodhound. Wild grizzlies have claws up to four inches long, to go along with dinner-plate sized paws. They have to eat 20,000 calories per day to sustain themselves. And the most incredible statistic? Grizzlies have a bite force of 1,200 pounds per square inch, enough to crush a bowling ball. Yes, a bowling ball. Ouch.

Apparently there used to be 100,000 grizzlies throughout North America. After decades of hunting and habitat destruction, only 1,500 grizzlies remain in the lower 48 states, of which 600 live in Yellowstone National Park. While still at very low levels, this is better than the all-time low of 200 bears in Yellowstone during the 1970s. At the time, bears had taken to eating from garbage dumps, which quickly became one of their primary food sources. The authorities subsequently decided to remove the garbage dumps. Ill-equipped to fend for themselves, the bears became more aggressive and human-bear incidents increased, resulting in the euthanization or removal of 200 grizzlies. Since the 1970s, the bears have returned to their natural food sources: roots, bulbs, rodents, leftover carcasses, salmon and other fish, and millions and millions of moths. One bear eats up to 40,000 miller moths in one day.

While it is certainly positive that the number of Yellowstone grizzlies has increased, and also that grizzlies are eating more moths and fewer Doritos, major issues concerning the survival of Yellowstone grizzlies remain. For bears, Yellowstone is basically an ecological island. Due to roads, human dwellings, and cattle ranches, the Yellowstone grizzly population continues to be separated from populations in Montana and Canada. As a result, the Yellowstone population is highly susceptible to changes to the environment. In particular, recent changes in climate seem to be affecting the migration of moths to the Yellowstone area. For grizzlies who return from hibernation to the same feeding areas year after year, the shock of removing a major food source could have very serious ramifications to the population.

As far as takeaways from this week's topic, I don't really have a profound message. If anything, I think the Yellowstone grizzly example reminds us of the impact exogenous forces can have on any kind of local environment. Grizzlies are fascinating, solitary, powerful creatures. While I don't necessarily want to raise one from birth, I will be rooting for their ongoing comeback.


  1. This dude is going to get mauled one day...I don't care...I'm calling it right now, even though I hope it never happens.

  2. Agree. Doesn't take much for a bear to lose its temper momentarily. Or even if it's just playing a game... one swipe is all it takes.

  3. 40,000 moths? How much does a moth weigh?

    At a reasonable count of 10-20 moths per oz that calculates out to 125 to 250 lbs in a day.

    That is good eating even for a large male in the 1000 lb range if you assume ideal capture conditions of (flocks? bevys? herds?)moths in a rock cave.


  4. Source on the 40,000 moth stat is Yellowstone:

    As for the weight, not sure how much an individual moth weights, but this is helpful:

    "Researchers estimate that in 30 days, a bear feeding extensively on moths can consume 47 percent of its annual energy needs. During peak feeding periods when moths are abundant, bears eat approximately 40,000 moths a day - equivalent to 20,000 kilocalories per day, or 38.5 Big Macs."

    So clearly this is their "beefing up" eating...

  5. Understood. I read the article. Run the numbers.

    Best TJK

  6. My two cents after running the numbers and doing some ballparking:

    Miller moths are pretty average-sized moths. If an average-sized butterfly is 0.1 gram ( ) and we assume the same for the miller moth, we have:

    10 moths/gram = 280 moths/ounce = ~4500 moths/pound

    So, 40000 moths could very realistically be c. 10 pounds, which makes sense to me as a ballpark figure. Ten pounds of moths is a significant contribution to the diet of any grizzly. Obviously these calculations depend on how much we say a moth weighs, but I think 10-20/ounce is too high (that's 1-3 grams/moth!)..

    Based on other articles about grizzlies eating up to 90 pounds food/day and at times feeding on exclusively miller moths, also called army cutworm moths ( ), I would guess that a grizzly could eat roughly 50-70 pounds of moths on a GREAT day.

    No offense, but I think 125-250 lbs/day is way too much.. Hope this is helpful.

  7. Excellent analysis!

    It highlights the fact this discussion is limited to speculation primarily because the ordinary and common practice of a specific species name included with the general common name is absent from the referenced Yellowstone Article.

    If the "Miller Moth" is in fact equivalent to the Pygmy Blue Butterfly your numbers are well within range. If however, the "Miller Moth" is the equivalent of the Queen Victoria Birdwing Butterfly then 2 to 3 grams per individual is not a fanciful guesstimate.

    The Colorado Extension Service offers this insight:

    ‘Miller moth’ is the term given to any type of moth that is abundant in and around homes.

    It is odd the simple facts (moth weight and scientific name) which would clarify the point of this article (moths are "Bear Food") is the hardest to acquire (anywhere!) and the least cited, (ditto anywhere) don't you think?


  8. TJK - first, meet my little brother (the budding naturalist with the excellent analysis above). I asked him to chime in on this, because he is far better than me at this sort of thing. As for your point on the simple facts, I couldn't agree more! When I wrote this, it was impossible to find any solid information on exactly what type of prolific, Yellowstone moth this could be. Thanks for reading and appreciate the discussion. Steve

  9. Indeed.

    Dittos here as well.

    All of us should be alert to compilations of information distributed to the public which lack
    any verifiable transparency.


  10. awesome post.. and I'm with Bob, he is probably to get mauled someday.
    Grizzly Man was an excellent yet disturbing documentary that everyone should watch.