Dave Hallock, Peak to Peak. One measure of the ecological well-being of a landscape is the ability of wide-ranging mammals, such as mountain lion, bobcat, elk, moose, lynx, bighorn sheep, bison, antelope, and black bear, to make long-distance movements. As a landscape becomes more fragmented by roads, towns, subdivisions, fencing, and trails, it gets harder for them to fully utilize their range. I have always thought that the presence of elk in western Boulder County was a positive sign, and the fact that they can still make a 20-mile movement between summer and winter range. But it is not always easy, and in some cases is becoming more difficult.

Elk make some of their most dramatic movements in the spring. The majority of herds in the county winter in the foothills. In late April and May they will move to montane parklands, such as Arapaho Ranch, Caribou Ranch, Wild Basin, and Tolland Park. They spend up to two months in the parks, have their calves, and then move higher to the Indian Peaks. The spring movement from winter grounds towards the montane parklands can be a quick, long-distance sprint.

I first became acquainted with local elk in the late 1970s after moving to Eldora. Over 200 cows, calves and young bulls were seen on the Arapaho Ranch in the spring. In summer, elk were seen on hikes in the Indian Peaks Wilderness and we wondered if these were the same animals. Winter hikes on Winiger Ridge and other places off of Magnolia Road would also encounter elk and the same question was raised - were all these encounters the same animals?

A major discovery occurred in the mid-1980s when I was caretaker at Walker Ranch Open Space, located off of Flagstaff Road west of Boulder and east of Gross Reservoir. Large groupings of elk were present on the ranch during winter. Colorado Parks and Wildlife (CPW) conducted a spring aerial flight to count elk. Rich Koopmann of Boulder County Parks and Open Space and Gary Berlin, the District Wildlife Manager for CPW, went up in a helicopter early one late-April morning. I told them that a large group of elk had been present on the ranch the previous day, so upon taking off from Boulder Airport they headed over the Flatirons for Walker Ranch. They didn’t find any elk at the ranch, but from the air were able to pick up a fresh trail made by the herd in the recent snow and wet ground. They followed the trail and found the herd near Tungsten Mountain, located just west of Reynolds Ranch and south of Magnolia Road. The evidence suggested that the elk herd had migrated approximately 10 miles that night!

In the late 1980s I had the opportunity to track radio-collared members of this herd, sometimes called the Winiger Ridge elk herd, for four years and found the same pattern: the spring migration generally included a 10+ mile jaunt over one night. The migration often occurred during the full moon period in April or May. They would normally stop short of the Peak-to-Peak Highway, regrouping for a day or two before making this potentially hazardous crossing. After crossing the Peak-to-Peak at night they generally spent the day west of the Town’s water treatment plant. The following night they would cross County Road 130 (the road to the high school and Eldora) to the Arapaho Ranch, doing this at several locations; several of the crossing sites were located between the Town and its water treatment plant, and others were west of the high school.

Since then I have noted the spring arrival of elk on the Arapaho Ranch as an annual passage. It is generally not hard to find where they crossed CR 130. The movement of a herd of hoofed animals will leave markings on the ground. The sand and gravel on the sides of the road are a good medium for tracking. It is easiest to track the crossing if there is snow on the ground. Spring movements can be tracked as much of the ground is moist. Routes used over and over again will develop a tread.

The locations for crossing CR 130 have been very consistent over the years. Some are between the Town and the water treatment plant, while others are west of the high school. But the area between the Town of Nederland and their water treatment plant appears to be one of the primary locations to cross. It is the shortest and most direct route from West Magnolia to the Arapaho Ranch. One of my larger sightings for this area occurred on May 6, 2013 at 4:30 AM. I was heading on a work trip driving east from Eldora, when I saw elk crossing the road well east of the water treatment plant. I stopped and turned off the vehicle, and over the next 5-6 minutes counted 46 animals heading north across CR 130 to the Arapaho Ranch.

In mid-May of 2017 we received a classic spring upslope storm that left three feet of snow on the ground. I was expecting the snow to delay the migration of elk. But on the Saturday morning (May 20) right after the storm, as I was driving past Nederland High School, elk were observed on the south-facing slopes of Park Hill on Arapaho Ranch. Driving further east past the High School and water treatment plant, there were numerous elk tracks in the snow on both sides of the road indicating where they had crossed. Peter Boyatt, District Wildlife Manager for Colorado Parks and Wildlife, accompanied me to look at the tracks. Why would they move higher in elevation right after the storm? Possibly to get to the south-facing slopes on the Arapaho Ranch, which cleared of snow before many other parts of the Nederland area.

We focus on elk because we know more about their movement. But other animal species are often observed using the same route in areas where wildlife movement is constricted. In the area between Nederland and their water treatment plant I have observed black bear, mule deer, moose, coyote, bobcat, and fox crossing CR 130.

In order to move between the Magnolia Road area and Arapaho Ranch, animals appear to move on the south and west sides of the Town of Nederland. A more direct link would be through Barker Reservoir (formerly Barker Meadow, likely once used by elk) and the town. Growth by the town to the south and west has the potential to cause the animals to alter or even abandon some of their current movement routes.

Wide-ranging mammals are often casualties of habitat fragmentation. The plains of the east county have lost bison and pronghorn in any meaningful capacity, and the presence of elk is more limited when compared to historic times. Bighorn sheep have never expanded into most of their historic range in western Boulder County since being reintroduced into the North St. Vrain canyon several decades ago. Most of our elk herds in the mountains still manage to make it down to the foothills for the winter, and a few make it onto the plains, particularly north of Boulder. One of the primary reasons for the acquisition of Reynolds Ranch Open Space along Magnolia Road was to protect the movement corridor of the Winiger Ridge herd. It should be noted that members of this herd also use a migration path heading west from the Arapaho Ranch that goes below Corona lift at the ski area; this route was recently protected from expansion of the ski area on its backside. Additionally, the movement corridor linking Winiger Ridge to Walker Ranch will become more constricted if Gross Reservoir is expanded.

As the human population continues to grow in number and covers more of the land, habitat fragmentation increases making it more difficult for wide-ranging animals. Elk are adaptable, but they have their limits. The elk herd in Eagle Valley, Colorado has recently declined by 50%. We are at an interesting time as both humans and wildlife are feeling hemmed in. For humans, it is based on trying to accommodate a growing population. For wildlife it is trying to maintain populations and historic patterns of movement.

Following are some of the April nature happenings in the Nederland area. Bird species returning from the south include Wilson’s snipe, band-tailed pigeon, broad-tailed hummingbird (end of the month), red-naped and Williamson’s sapsuckers, tree swallow, ruby-crowned kinglet, yellow-rumped warbler (end of the month), common crackle, fox sparrow, and song sparrow. Late April is the peak time for great horned owls to hatch. April is a prime time for hearing the calls of our small forest owls: northern pygmy-owl, northern saw-whet owl and boreal owl.

Mammals tend to be emerging or moving. Snow level permitting, elk will begin a movement from their winter grounds to transitional range. Chipmunks and ground squirrels may be seen during periods of mild weather. Black bears are emerging from dens in March and April; their favorite foods at this time of year are vegetation and carrion. The peak time for bobcat young to be born is April and May. Mink breed from late February until early April. Long-tailed weasel litters are born in April and May.

Butterflies that overwinter as adults, such as mourning cloaks, tortoiseshells and commas, may appear during periods of mild weather. Pasque flowers may be found blooming on south-facing hillsides if the weather is mild enough.

(Originally [published in the April 11, 2019, print edition of The Mountain-Ear.)