Desert Bighorn sheep just might be the wildlife attraction at Zion National Park in southwestern Utah. And while the herd has grown quite a bit in recent years, park officials want to get a better grip on managing the animals.
Since desert bighorns were returned to the park in 1973, the resident herd has grown to more than 500 individuals. While the Utah Division of Wildlife Resources manages those sheep that roam outside of Zion, park biologists handle the sheep inside the park.
According to Park Service wildlife biologist/disease ecologist Ryan Monello, disease is one of the greatest concerns surrounding the park's sheep herd. Contact between bighorn sheep and domestic sheep or goats (all of which are behaviorally attracted to each other) can lead to outbreaks of respiratory disease, and may have long-term impacts on population levels of bighorn sheep, according to park officials.
And yet, population drops have also occurred in the apparent absence of contact with domestic sheep or goats, they add.
"Such declines have been attributed to various factors including disease transmission from adjacent bighorn herds, high densities and related nutritional issues, human disturbance, loss of habitat, weather conditions, and infection with parasites such as lungworm or mites," a park release said. "Active desert bighorn sheep management is considered necessary to reduce risk of disease transmission and catastrophic die-offs of bighorn populations."
The goal of developing a management plan is to protect the established Zion bighorn sheep population by following the Utah Statewide Bighorn Sheep Management Plan and the Western Association of Fish and Wildlife Agencies (WAFWA) Wild Sheep Working Group recommendations.
Most often, bighorn sheep population numbers are managed through hunting or using transplant efforts in order to reduce localized densities. But since hunting is not a legislated purpose of Zion, a trap and transfer process would be one potential management option. The frequency and number of bighorn captured typically varies between 20 and 100 sheep for each transplant effort, but would be variable and dependent on local conditions, herd demographics, and the agency level of concern about disease transmission, the release noted. These bighorn would be transplanted to supplement an existing small herd or start a new population, but with the primary objective of protecting the source herd.
Zion officials are going to prepare an Environmental Assessment to provide a decision-making framework that explores a reasonable range of alternatives to meet project objectives, evaluates potential issues and impacts to park resources and values. That plan also would identify mitigation measures to lessen the degree or extent of these impacts, they said.
The public can participate in the EA preparation during this initial public scoping period for development of the alternatives, and during future public review of the EA. At the time being, park officials are asking for concerns and suggestions for the management plan. They are taking public comments through March 19 at this site.