Zion National Park Wildlife Program Manager Cassie Waters had good news for the people attending the Zion Canyon Field Institute’s Fern and J. L. Crawford Lecture Series in Springdale on Thursday and a warning for the future. She said that before 1800, there were probably millions of Bighorn Sheep in North America, and a lot of them lived in what is now Zion National Park. By the 1950s they were all gone from Zion Park.
In the 1970s, state and park officials started a program to reintroduce Bighorn Sheep to Zion Park. Early mistakes made park officials believe that the program had been a failure by the early 1980s, but it wasn’t. The few survivors of those early reintroductions were slowly growing in number, and today Zion Park’s herd is big enough to contribute to reintroductions in other places. Waters said that it’s estimated that Zion Park’s herd numbers about 527 individual sheep now.
In addition to Zion Park, Desert Bighorn have spread out into the adjacent Canaan Mountain Wilderness, managed by the Bureau of Land Management, and north toward the border of
Zion Park. There is a constant risk that they will come in contact with flocks of domestic sheep on private land and areas where grazing allotments for sheep still exist. Changes in BLM grazing allotments have eliminated many of the risks of the past and have allowed the herd to grow as big as it is. Waters said that Springdale itself still has flocks of sheep which create some of the risk.
The problem is that domestic sheep are carriers of bacterial infections that are deadly to Bighorn Sheep. The domestic sheep have immunity to the effects of the infections and seem to be quite healthy, but direct contact with Bighorn Sheep can create epidemics — Waters referred to them as “die off’s” — which have eliminated whole populations in some places. In decades of experience, Bighorn Sheep show no signs of developing their own immunity and efforts to develop vaccines for the Bighorn Sheep have not been successful. The stark reality is that in a specific area, it’s possible to have domestic sheep or Bighorn Sheep but not both.
The primary action that state and national wildlife managers can take to prevent domestic sheep from infecting and decimating Zion Park’s herd is to simply ensure that the two populations don’t come in contact by moving, or in some cases eliminating, the Desert Bighorns from areas where they might come in contact with domestic sheep.
This has been the primary goal of transfers that have taken place in recent years.
In addition to providing a Desert Bighorn wildlife experience for people in areas outside of Zion Park, Waters described new populations of Desert Bighorns as an “insurance policy” in case a die-off of the herd inside the park requires a restoration like the one in the 1970s. Since herds in other places have been lost in the past, there is no guarantee that it will never happen in Zion Park.
Desert Bighorns have fascinated people for as long as people have been here. A question from the audience noted that Bighorn Sheep are more prominent in native American pictographs and petroglyphs than, for example, deer. For now, tourists traveling the scenic route through Zion Park have a Bighorn experience on the east entrance road that they can take back with them.