Yellowstone area grizzlies increasingly chow down in safety near remote alpine meadows

Partial salvation for griz — moths-

Grizzly bears in the Greater Yellowstone eat more kinds of food than the average person. It is now known that these Greater Yellowstone ecosystem grizzlies consume 266 identified plant and animals species.

Greater Yellowstone bears do have to try harder because two of their previously major sources of food have all but disappeared — Yellowstone cutthroat trout and whitebark pine nuts. It was known that the big brained bears were finding substitutes for the loss, such as the increasing numbers of elk carasses brought down by the wolf packs in the area. The bears steal them from the wolves. Then there are a big variety of other things, from various grasses and sedges, to thistles, ants, beetles, grubs, rodents, and berries. Apples, dog food, grain in feeders, sacks and troughs, and livestock too are also yummy and nutritious bear food. The later have strings attached, however. The strings lead to guns.

A nice thing about the fat cutthroat trout and fat rich whitebark pine nuts was that people didn’t mind and the nuts grew in the heights just below the alpine tundra. In a bad turn of events, fire, drought, and whitebark pine blister rust got most of the pine nut trees. The voracious and ecologically useless lake trout ate most of the cutthroat. Parasitic whirling disease got most of the cutts in the streams. Increasingly effective use of nets seem to be reducing the lake trout in a planned Park Service campaign against the non-native lunkers.

What, however, if there was another safe and big source of fat and protein for the grizzlies for which they would not be shot? There is such a source, and it has been known (by people) since the mid-1980s. It was then it was discovered that a portion of the grizzlies had discovered huge agglomerations of army cutworm moths. These drab little balls of fat and protein (72 and 28%) flew to the alpine meadows on the highest peaks in late June to feed all summer on the alpine wildflower nectar. The moths fed at night. In the daytime, they lodged themselves under rocks and talus slides for protection from UV,  and from the often violent thunderstorms with hail. The bears came and turned over the rocks to slurp up from as much as 20,000, to even 40,000 calories a day.

The flowers and moths disappeared as September came. That’s when elk hunters around the Park boundaries began to ride their horses up into the remote alpine zone.

Not all the grizzlies in the Yellowstone went up to eat moths, however. It is likely that many had not learned about them, or perhaps they had access to other foods. Now though, the Interagency Grizzly Bear Study Team has reported that more and more grizzlies are using these moth sites as a source for food over the course of the last three years.

Aerial observations of 29 of these moth sites in the heights of the Absaroka Range found 470 grizzlies. In 2014 there were 220 unique bears found visiting the sites. All told 37 sites were discovered. Grizzlies visited 80% of them.

Agriculturalists are not enthusiastic about the army cutworm larvae — the actual worms which can mow down some crops like an army. They get hit with pesticides. As a result there has been worry that grizzlies might eat enough moths to be poisoned.  However, a study done in 1999-2001 showed just traces of pesticides in the moths at sampled “mothfields.” These levels of pesticides were not high to harm bears no matter how much moth munching they did.

A web search will lead the interested to a number of scientific papers on the subject of bears and moth sites.



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  1. Ken Watts Avatar
    Ken Watts

    Could the white bark pines have been saved by spraying?

    1. SAP Avatar

      Ken, the major source of whitebark pine mortality was an epidemic of native mountain pine beetles.

      As Ralph notes, the epidemic was brought on by drought and by warming temperatures. Warmer temperatures in summer allowed beetles to thrive at higher elevations, where it used to be too cool for them. Drought meant that trees were less capable of defending themselves against beetle attack — not enough moisture to produce enough pitch to repel/drown beetles as they bored into trees.

      The scale and pace of the beetle epidemic — along with the rugged terrain of many whitebark stands — made spraying or any other intervention mostly impractical. I’ve been involved in protecting small numbers of trees from beetles — these were whitebarks we identified as showing resistance to the invasive fungus, blister rust. Our protection strategies involved beetle repellent packets that we attached to trees every four weeks during the active season for beetles; or spraying a nasty chemical called Carbaryl on the trees, which was just a once-per-season application, but required way more equipment (a “cherry picker” to allow the person doing the spraying to reach the upper parts of the tree). Aerial spraying of Carbaryl would have had a lot of negative consequences, since it’s likely carcinogenic.

      So, I’m inclined to think that spraying wasn’t an option.

      1. Ken Watts Avatar
        Ken Watts

        Carbaryl (SP) is used on fruits and vegetables throughout the nation. I believe it is a very benign chemical and not carcinogenic. I will check my sources. I am aware of a case where it was used very effectively used to control pine bark beetle, fir beetle and spruce bud worm. The result was a very healthy forest.

        Spraying by helicopter may have been practical in isolated stands.

        1. Mcan Avatar

          Carbaryl (Sevin is the most popular brand name) is HIGHLY toxic to fish, bees, aquatic invertebrates (and this in numbers high enough to mean that it is dangerous to entire ecosystems).

          Carbaryl on leaves, degrades in a few days; in soil it takes a year to get down to 3% of original amount.

          Although it appears not to bioaccumulate in mammals, convulsions, coma, paralysis, death, and some specific organ problems result.

          Not very carcinogenic, according to EPA, but as you see above, environmentally highly dangerous, as are just about all pesticides in one way or another. If cancer is your only worry in life, drink up (but don’t spit it out on Earth).

          1. Ralph Maughan Avatar
            Ralph Maughan

            I have noticed folks discussing various pesticides and cutworms, etc.

            It should be noted that the study I got my information from examined the army cutworms for amounts or traces of 32 different pesticides.


          2. Yvette Avatar

            I’m not familiar with Carbaryl, but it bound to detrimental to amphibians, which are taking a big hit from our pesticides and herbcides.

  2. Ida Lupines Avatar
    Ida Lupines

    These levels of pesticides were not high to harm bears no matter how much moth munching they did.

    Do we know this for certain? Are we using even more pesticides today? Do they accumulate in tissue?

    1. Elk375 Avatar


      Several years ago I did some business with a women and her husband; she was finishing up her doctorate in wildlife biology at MSU and her dissertation was on grizzly bears and moths. We talked about the moths and I ask her where the moths went when they left Yellowstone National Park, her consensus was that the moths went to the Pryor Mountains for part of the year. No one really knew for sure. There is no agriculture in the Pryor Mountains or pesticides.

    2. Ralph Maughan Avatar
      Ralph Maughan

      Ida Lupines,

      Here is part of the abstract I read from this article in Chemosphere. Sept. 2006: Assessment of pesticide residues in army cutworm moths (Euxoa auxiliaris) from the Greater Yellowstone Ecosystem and their potential consequences to foraging grizzly bears (Ursus arctos horribilis) Hillary L. Robisona, , Charles C. Schwartzb, Jim D. Pettyc, Peter F. Brussarda.

      “ACMs [army cutworm moths]contained trace or undetectable levels of pesticides in 1999 and 2001, respectively. Based on chemical levels in ACMs and numbers of ACMs a bear can consume, we calculated the potential of chemicals to reach physiological toxicity. These calculations indicate bears do not consume physiologically toxic levels of pesticides and allay concerns they are at risk from pesticides transported by ACMs. If chemical control of ACMs changes in the future, screening new ACM samples taken from bear foraging sites may be warranted.”[boldface mine]

  3. Ida Lupines Avatar
    Ida Lupines

    With grizzly bears in the ecosystem proposed for delisting by the U.S. Fish and Wildlife Service, ensuring that the bears have enough to eat is paramount to making that decision. The USFWS director could hand down a delisting decision right away or months from now, according to Chris Servheen, the USFWS grizzly bear recovery coordinator.

    Many bear biologists insist that grizzly bears are adaptive enough to find different food sources, even if whitebark and trout numbers are down. Some environmentalists argue just the opposite. If the bears are delisted, the issue will likely be contested in court.

  4. snaildarter Avatar

    I’m concerned about Grizzly Bears being dependent on anything Monsanto wants make money killing. There are no honey bees left in my neighborhood.

    1. rork Avatar

      Are we gonna blame Monsanto for lightening strikes next? At least aim properly before you let the arrow go.
      PS: Honey bee is the white man’s fly, and we no longer permit folks to house them on state rec areas near me in MI (we used to), cause we have native pollinators to seriously worry about.

  5. Nancy Avatar

    Be interesting to know the dent, given the increase of grizzly bears, has made on those crop damaging moths.

    1. TC Avatar

      Given the plague of miller moths in Wyoming this summer, I’d say little. Gets tiresome shooing the noisy fluttering things outside all night and cleaning the dead ones out of vehicles, homes, garages, etc. by day. The bats and swallows seem to love ’em as much as the bears, and anything that mimics them sure gets trout excited. Of course, the moths are not agricultural pests – it’s the caterpillars that eat up crops, gardens, lawns, and most things green. They too can get tiresome, but native predators do a pretty good job of keeping a lid on them most years. In both life stages they provide a lot of fatty food for a lot of enjoyable wildlife.

      1. Nancy Avatar

        “Of course, the moths are not agricultural pests – it’s the caterpillars that eat up crops, gardens, lawns, and most things green”

        Thanks TC, aware that the worms did the damage but how many moths don’t make the return trip (to lay eggs) now that there is an increase in grizzly bear populations, taking advantage of the moths?

        Recall a newspaper headline in Billings, Mt. years ago (where I lived briefly) proclaiming “It’s Miller Time!” Which explained to a “T” your comment

        “Gets tiresome shooing the noisy fluttering things outside all night and cleaning the dead ones out of vehicles, homes, garages, etc. by day” 🙂

  6. Leslie Avatar

    Anecdotally, I was in the Southern Winds this year and the Whitebark Pine crop was over 100/cones per tree! In general, my observations show that while where I live in the Absarokas over 90% of the Whitebarks are functionally dead, only about 40% of the whitebark pines in that area of the Wind River range [Washakie Creek] were dead.

    That speaks for enlarging the PCA and solving the problems in the Green River Valley [the grizzly corridor to the Winds] before delisting can occur.

    The Winds are great habitat for grizzlies.

  7. monty Avatar

    What is the prognosis for killing more lake trout and thus improving native trout survival rates. We humans seem to be good at “killing nature” so let’s apply this talent to the lake trout!!!!

    1. Elk375 Avatar

      They are going as fast as time and the elements allow. All lake trout caught must be killed, gill netting all summer and fall and now electro shock therapy zapping the eggs in the spawning redds.

    2. rork Avatar

      You can read articles all day about that. One summarizes “Distribution netting shows a very positive trend in YCT juvenile and mid-year age classes netted over the past two years. This is supported by increasingly positive angler reports of YCT caught, so it appears there may be a rebound of YCT.” (YCT = cuts). They are netting fewer Lake trout per unit effort, and less big ones. It’s pretty expensive, but cool, and they are getting craftier every year. Send money. This is war.

      1. Nancy Avatar

        “Send money. This is war”

        Send Money? But who laid the ground work that brought about this war, Rork?

        1. rork Avatar

          Tell us what you think should be done if you have an opinion, rather than leaving puzzles. I’m guessing you are talking about who to blame. Go ahead and do that (I could write at length myself), but don’t forget to then tell us your plan for YCT.

          1. Nancy Avatar

            How about an Angler’s Stamp Rork? Or bump the tax up slightly on fishing equipment.

  8. monty Avatar

    Ask for donations at Yellowstone entrance locations. I would give $’s to this effort. When I think of the $’s spent on wars it makes me want to go “postal”.


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Ralph Maughan