JACKSON HOLE, WYO – During the partial federal government shutdown this past month, many refuge management activities and services were on hold. One task, though, was deemed essential and continued throughout the duration: measuring the amount of standing forage available for wintering bison and elk. This, along with assessing snow conditions and monitoring the numbers and distribution of the herd, are critical components in determining each season if supplemental feeding will be necessary.
The initiation of feeding in any given year depends on a number of variables, including elk and bison numbers on the refuge, the timing of their migrations to the winter range, temperatures, snow depths, and the accessibility of standing forage.
A common misconception is that supplemental feeding on the refuge is mandated by law. Though it is a longstanding wildlife management approach on the refuge, it is not required by any federal law or statue. Nor was feeding a purpose for which the refuge was established. Instead, supplemental feeding on the refuge historically began to mitigate conversion of former winter range to other land uses.
The refuge’s current management plan that guides bison and elk administration on both the national wildlife refuge and Grand Teton National Park includes a reduction in the refuge’s feeding program due to concerns related to concentrations of animals and the increased risk of disease. Though initiation of the feeding season tends to occur in late January, the more noticeable and flexible variation has been when the feed season concludes. Here, the dates can vary as much as a month, ranging from the middle of March until late April.
Last season presented an opportunity to bypass feeding altogether. With warmer than average temperatures last January and February and a visible lack of snow in many areas where elk typically winter, the refuge did not provide supplemental feed, making it the first time since 1981.
But every year is different. Spring rains can set up a good growing season and, combined with the refuge’s irrigation program, can result in a good forage production year. If bison herds remain further north of the refuge and don’t graze on refuge grasses and forbs in late summer and early fall, it can preserve forage until further into the critical winter period.
During forage assessments done concurrently by the U.S. Fish and Wildlife Service and the Wyoming Game & Fish Department beginning in December, biologists look at not only the amount of vegetation remaining from the summer growing season but the availability and ease of access to the forage by wintering wildlife. Heavy snow, icing, or crusting can form a barrier to foraging activities, making it difficult for elk to paw through the ground cover to reach the remaining herbaceous plant material.
Field staff measure the amount of grasses at roughly four to six key index sites in areas that represent the highest quality forage on the southern end of the refuge. They then translate those calculations into an estimated amount of pounds per acre. Supplemental feeding is often recommended when available forage decreases to below 300 pounds per acre. Though the threshold still represents adequate forage levels to sustain groups of elk and bison, it marks the point when elk have often been observed leaving the refuge for private lands in Spring Gulch.
Protocols developed with the Wyoming Game & Fish Department for initiating supplemental feeding also include elk movements. Factors such as co-mingling of wildlife with livestock, other damage on private lands, and observations of increased elk movement near highways and other main travel routes are also part of the equation.
Elk behavior plays a role in the decision-making process, too. This past week, refuge staff has observed groups of elk adjacent to the Twin Creek subdivision and near the Visitor Center on North Cache Street in Jackson, both indicators that elk may be staging to move onto private lands.
Standing forage calculations have declined from 1,145 pounds per acre in mid-January to 308 pounds measured late today. Combined with a snowstorm that brought several feet of additional snow to the valley floor over the past few days, the refuge staff is gearing up to begin supplemental feeding this week. How long the feed season will last depends upon future winter conditions, elk behavior, and a management direction to shorten the season when possible to reduce the risk of disease, specifically the growing threat of chronic wasting disease.
