The North Cascades: just right for grizzly bears
Conservation Northwest / Jul 20, 2016 / Grizzly Bears, North Cascades
By Chase Gunnell, Communications Director
One of the most common questions we get about grizzly bears is whether the North Cascades has the right habitat and food for them. Conservation Northwest reached out to Bill Gaines, Ph.D., bear ecologist and director of the Washington Conservation Science Institute, for his take on why the North Cascades is, as in the Goldilocks tale, “just right” for grizzlies.
“The combination of really high quality habitats in really remote areas makes the North Cascades relatively unique in the lower 48 states and is a primary reason that grizzly bear recovery is being pursued here.” –Bill Gaines, Washington Conservation Science Institute
Want to learn more about the North Cascades Grizzly Bear Recovery Zone? Check out a map here.
What was the historical presence of grizzly bears in the North Cascades?
We know from trapping records kept by the Hudson’s Bay Company from forts that were in and around the North Cascades that grizzly bears were present. For example, between the years of 1827 to 1859, Hudson’s Bay Company records show that 3,788 grizzly bear hides were shipped from three forts in or near the North Cascades. Likely not all of these came from the North Cascades but this probably had a considerable impact on the grizzly bear population in the North Cascades. Additional information is available from historical accounts of government trappers, hunters, and explorers. For example, while surveying the U.S.–Canada border in the 1850s, Custer documented observations of several grizzly bears above the North Fork of the Nooksack River. Other grizzly bears were killed or trapped such as the grizzly bear killed by government trapper Pete Peterson in the 1920s near Mazama. In 1967 the last legally killed grizzly bear was taken from an area near Washington Pass (grizzly bears were listed in 1973). Collectively, this information suggests that there once was a relatively large population of grizzly bears that occurred throughout the North Cascades.
When people think about grizzly food, they often think elk calves or salmon. But I understand that in areas like the North Cascades and Yellowstone, the average grizzly diet is mostly vegetation. What types of plants are found in the North Cascades that would make up a grizzly’s diet?
Yes, bear diets can vary quite a bit by season and on the eco-system they live in. But generally 75-85% of their annual diet is composed of vegetation. When we were evaluating potential food sources for bears in the North Cascades, we looked at the available research on bear diets and developed a list of 124 plant species they feed on. We then compared that list to the data we collected on plants in the North Cascades based on 1,726 vegetation plots. We found that 100 of the 124 species of plants that are bear foods occur in the North Cascades. In fact, when compared to some of the other ecosystems where bears live, we have a wide diversity and abundance of plants for bears to eat. Some of the really important plants will be berry producing shrubs, such as huckleberries (of which there are seven species in the North Cascades), salmonberry, red bilberry, choke-cherry, bitter cherry, and many more. We also found that some habitats were especially rich in bear foods, such as lush wet meadows or avalanche chutes, both of which are plentiful in the North Cascades.
What about insects? Would they be a large part of a grizzly bear’s diet here, and if so what types of insects?
Typically insects are not a large part of a bear’s overall diet, though they may be of local or seasonal importance. We have documented insects in the diets of black bears in the North Cascades, especially ants. In other ecosystems, army cutworm moths can be an important food source. We have done some limited surveys for army cutworm moths in the North Cascades and found a few sites where they are concentrated. However, without local research on grizzly bear diets, we don’t really know how important these moths may be.
The North Cascades has an amazing diversity of wildlands, from rugged alpine basins to dry pine forests. What sort of habitat would a grizzly bear be expected to use each season in the North Cascades?
Typically, grizzly bears den at higher elevations where snow cover is substantial. They might be expected to leave their den between mid-March and mid-April, and move down to lower elevations that are snow free. This is the time of year they might feed on winter-killed deer and elk or take an occasional fawn or elk calf. So, for a time in the spring they are down in some relatively low country, and on the east side this is relatively dry country. As spring progresses into early summer we’d expect bears to move into higher elevations, taking advantage of roots, tubers, and plants that are growing after the snow recedes.
Plants such as spring beauties and avalanche lilies. By midsummer, some of the early shrub fruits will start to come on, such as service berry, mountain ash, elderberry, and others. As summer progresses, more of the shrub fruits come on and we’d expect grizzly bears to move into the high elevations to feed in those high-elevation huckleberry meadows. They’d likely stay in these areas late into the summer and fall for as long as the berries are available. Some bears may move down to lower elevations to take advantage of fall salmon runs. Fall is an important time for bears as they are putting on weight in the form of fat to get through the long winter denning period. They need places with concentrated food resources and they may forage throughout the day and night to get the needed calories.
Generally, the moister productive habitats that occur on or near the crest of the North Cascades are the most productive and likely to be highly used by grizzly bears. Fortunately, we have an abundance of these habitats, and many occur in national park and wilderness areas where bears can also find places away from roads, campgrounds, and urban areas. That combination of really high quality habitats in really remote areas makes the North Cascades relatively unique in the lower 48 states and is a primary reason that grizzly bear recovery is being pursued here.
Is there anything else people should know about why the North Cascades are high-quality grizzly habitat?
The diversity of elevation zones and moisture gradient work together to create a wide diversity of vegetation types and habitats. For example, the North Cascades National Park contains 1,630 vascular plants species, the most of any park in the national park system! It is this diversity that creates such amazing habitats for bears and other wildlife. In addition, the abundance of wild areas, really rugged and remote, provide the opportunity for bears to find really good habitats and be in places that limit their exposure to people.