Originally published in Points West magazine in Winter 2002
The Nature of Spring in Yellowstone Country
By Dr. Charles R. Preston
Willis McDonald IV Senior Curator, Draper Natural History Museum
There is something infinitely healing in the repeated refrains of nature—the assurance that dawn comes after night, and spring after winter. —Rachel Carson
I couldn’t believe my eyes when I peered outside the tent. The ground was swathed in a quilt of white, and big, fluffy flakes of snow filled the sky! The only sounds were the lonesome calls of ravens somewhere in the milky distance. Just two days earlier, I had been surrounded by the crystalline songs of northern cardinals and Carolina wrens, the brilliant pink and white blossoms of redbud and dogwood trees, and the sweltering 90-degree heat and 90-percent humidity of spring in the Arkansas Ozarks. But I wasn’t in Arkansas anymore, and this snowy introduction to springtime in the Rockies was a bit unexpected. I had visited the high country of the Yellowstone region before -but only in midsummer. This time, I was taking part in an expedition assigned to bring back western plant and animal specimens and photographs for research and educational programs for an Arkansas museum. It was during that expedition nearly thirty years ago that I began a lifelong infatuation with the wild life and wild landscapes that continue to distinguish the Greater Yellowstone region from the rest of our planet.
Wildness, almost by definition, is chaos. It is messy, sometimes inconvenient, often dangerous, and usually unpredictable. But even in the midst of chaos, nature lays down patterns that repeat themselves with enough regularity to give us some sense of anticipation and perhaps comfort. In temperate regions of the world, seasons change with comforting regularity in response to the position and orientation of the Earth in relation to the Sun. Seasonal changes don’t occur overnight to match calendar designations, however. They unfold gradually, with new signs of transformation revealed daily. Some of these signposts are dramatic, like the appearance of wildflower carpets in late spring, or the multihued tapestry of autumn leaves. Other harbingers of seasonal change are far more subtle to human senses. And, as I found out during my first spring expedition to the Rocky Mountains, seasonal changes follow a vastly different script in different geographic areas and environments.
Learning to recognize signposts that herald the seasons adds greatly to an improved understanding and appreciation for the patterns of nature. The following are some annotated excerpts from field notes I’ve recorded during spring expeditions in the last few years. These are mere snapshots documenting a fraction of the story that unfolds each year, as spring captures the highlands and lowlands of the Greater Yellowstone region.
Entry: 22 March 2001… Wapiti Valley, North Fork corridor of Shoshone River, between Wapiti, Wyoming and east gate of Yellowstone National Park…morning overcast, with winds gusting to about 25 miles per hour; temperature hovering about 30 degrees, F…no snow falling, but patches of snow remain on ground from last week’s snowfall…Absaroka Mountain peaks still covered with snowpack, but lighter than normal for this time of year…hope to shoot video and still photos of bighorn sheep for upcoming exhibits in the Draper Museum of Natural History…heard two great horned owls calling back and forth across the valley early this morning…saw a rough-legged hawk perched on a utility pole in the valley just east of Shoshone National Forest boundary…adult bald eagle flying above Shoshone River nearby…finally found large group of bighorn sheep grazing and loafing in sagebrush flat near U.S. Forest Service Ranger Station…16 rams in the group…two of the smaller rams sparring with some light head-butting…several magpies hanging around the bighorn sheep.
Remarks: Most visitors from the Southern or Midwestern U.S. would not recognize March in the Rocky Mountains as springtime, but subtle events are occurring at this time that foreshadow more dramatic transformations to come. As we found on that late March day in Wapiti Valley, snow still covers most of the high country in early and mid-spring, and may even extend well into the lower, intermountain basins. This is usually the period of greatest yearly snowfall—heavy, water-laden crystals that help top off the alpine snowpack that will melt into summer and nourish lowlands many months and many miles away. The depth of the snowpack determines how much water will be available for wildlands and irrigated croplands during the typically dry summer. Ambient temperatures can fluctuate widely from day-to-day, challenging the versatility of any outdoor enthusiast’s wardrobe.
Birds of prey are among the most conspicuous wildlife species in many areas, and keeping tabs on their comings and goings is a good way to mark the seasons. Most great horned owls in our area begin nesting in February and early March. These large, aggressive owls don’t build their own nests; instead they commandeer nests built and used by ravens, hawks, or eagles in previous years. Because the owls begin nesting earlier than most hawks and eagles, they often have first choice of former nest sites. By late March, the eggs in many great-horned owl nests have hatched, and adults are busy feeding their hungry nestlings. The youngsters will remain in the nest for 9 – 10 weeks before they are ready to fly. The two owls we heard at first light on 22 March might have been reminding one another of the territorial boundaries they had established much earlier in the year.
The rough-legged hawk we spotted on this field trip was a winter resident. Many rough-legged hawks can still be found searching open fields in foothills and lowlands for mice and voles in early March, but they begin their annual northern flight to breeding grounds in northern Canada and Alaska by mid-March. They are typically absent from our region by early April.
By mid- March in the Greater Yellowstone region, most resident, adult bald eagles are already incubating eggs. The eagle we spotted on the 22 March field trip might indicate that a pair of bald eagles was nesting nearby, though we did not find any active nest site. Nest site characteristics can vary greatly among bald eagle families, but each nest site will be within eagle eyesight of water.
The bighorn sheep we found and photographed were on their critical winter range in Wapiti Valley. Elk, mule deer, and even a few bison migrate down from the high country and share space and other resources through the winter in Wapiti Valley. In response to weather, food resources, and other factors, these animals typically begin migrating back to higher elevations in March and April. You can often see ewes with newborn lamps scurrying along the rugged Absaroka peaks and ledges above Wapiti Valley in late spring.
During winter months, bighorns often graze near roadsides and are unfortunately easy targets for poachers. The two bighorn specimens displayed in the Draper’s Alpine Environment were confiscated from poachers. These two magnificent rams were illegally killed on Christmas Eve 2000 in Wapiti Valley. The two poachers were caught and convicted thanks to a tip from the public, and heads-up investigation by the Wyoming Game and Fish Department (WGFD). The WGFD made it possible for us to include the specimens in our exhibit.
Entry: 06 April 2000… sagebrush-steppe bench in Bighorn Basin…early morning…sky mostly overcast, but with a few stars visible…no wind…roads and ground clear of snow…temperature 43 degrees F… I’m getting an early start to observe and document greater sage grouse booming lek… I slipped into position at the lek site well before sunrise to avoid disturbing the birds…after quietly listening for about 15 minutes, I heard the first eerie “balloompp, balloompp” of a booming male…by sunrise at least 20 males strutting and booming to impress only five attending females…four of the females hanging around one large, aggressive male near the center of the lek.
Remarks: One of the most dramatic events signaling the onset of spring in the Greater Yellowstone region is the elaborate courtship ritual performed by the greater sage grouse. Males select a large, relatively open area as a stage for attracting mates. The area is called a lek. At dawn and dusk in late March and early April, each male defends a small site within the lek, where he vocalizes (“booms”) and displays his plumage, experience, and energy in a ritualized “dance”. Up to forty males and dozens of females may attend a breeding lek. Females are presumably most stimulated by the male(s) who demonstrate traits that will help offspring survive and successfully mate. It remains unclear just what traits are most important in stimulating females, and it is doubtful that females are aware of the ultimate consequences of their mate choice. We do know that larger, older males tend to attract the most females, but the most important trait might be the ability to defend a preferred area within the lek—apparently not all sites within a lek carry the same cachet!
Sage grouse are limited to sagebrush-dominated environments. Significant sagebrush environments and sage grouse populations remain in the Bighorn Basin and other areas of Wyoming, but scientists consider the sagebrush-steppe ecosystem to be critically threatened through much of its former range. Sagebrush environments, so closely tied to the myth and reality of the American West, are fast disappearing from the western scene to make way for croplands, livestock grazing, and especially housing developments. We’ve recreated a slice of Wyoming sagebrush-steppe, including a sage grouse booming lek, in the Plains/Basins Environment of Draper.
Entry: 07 June 1997… Lamar Valley, Yellowstone National Park…late afternoon…light mist and overcast earlier, but sky now clear, light breeze from northwest…temperature 51 degrees F… I’m leading natural history tour from Denver to study Yellowstone’s northern range and observe ungulates and wolves…aspens completely leafed out…larkspur and silver lupine in bloom…several elk with newborn calves, a few hundred bison, mule deer, pronghorn in Lamar Valley…four wolves resting until lead female rousted others…wolves split up and one black wolf ran through small herd of elk…other wolves chased one cow elk that split from herd…she got away this time…just before dark we saw a grizzly sow and two cubs feasting on a large elk carcass in a meadow near Lamar River…wolf kill, grizzly kill, winter kill?…bear property now!
Remarks: Lamar Valley is often called the Serengeti of North America. Although the numbers and diversity of animals don’t really rival those of the grasslands of East Africa, the landscape and assemblage of large grazing animals and predators found in Lamar Valley is unparalleled in North America. Spring brings large numbers of predators and prey together each year in this broad, lush valley. Ungulates (i.e., elk, bison, deer, pronghorn) and wolves give birth and nurture their young, and grizzly and black bears support cubs born during winter sleep. Bears typically emerge from hibernation by late March, depending on weather and their physical condition going into hibernation. In spring they feed largely on winter-killed carcasses, a wide assortment of plants (e.g., biscuitroot, yarrow), spawning cutthroat trout, and an occasional elk or moose calf.
The restoration of the gray wolf to Yellowstone National Park in 1995 returned a key player to the ecosystem that evolved and prevailed in the Greater Yellowstone region for approximately 10,000 years before Euro-American settlement. But the presence of wolves and grizzlies is not universally embraced. Most of the Greater Yellowstone region has changed significantly since Euro-American settlement. Human population, development, and economic interests continue to grow in the region, creating increasing opportunities for conflicts between humans and large predators. It has become clear that, with adequate habitat resources, wolves and grizzlies can tolerate living in close proximity to humans; it remains unclear if humans can tolerate living in close proximity to wolves and grizzlies.
The trip I led to the Greater Yellowstone region in 1997 proved to be a key turning point in my life. It was during that trip that I first visited Cody and the Buffalo Bill [Center of the West]. Both made a strong, positive impression on me, and when I learned about the opportunity to lead the development of the Draper Museum of Natural History, I couldn’t wait to throw my hat in the ring. I relive that June 1997 field trip every time I review my field notes. Keeping a field journal is a great way to relive old memories and keep track of environmental patterns and changes. Follow the lead of our resident Draper Natural History Museum “naturalist and tour guide,” B.A. Ware, and record your own observations of the sequence of natural events wherever you are during the spring of 2003.