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Bighorn Sheep: Prehistoric Past, Present, and Future

By Mike Cox

Nevada has a rich history of bighorn sheep. Nevada is blessed with a vast canvas of rugged and diverse mountains – a perfect natural landscape for bighorn sheep. Prehistorically, wild sheep first showed up in North America, crossing the Bering land bridge from Siberia to Alaska during the Pleistocene Epoch (about 750,000 years ago) and slowly dispersed into what is now western U.S. maybe 200,000 years ago. Some of the oldest bighorn fossils in Nevada that have been radiocarbon dated by paleontologists are: 42,000 years ago from the Diamond Mountains (Eureka County), 38,000 years old in the Sulphur Springs Range (Elko County) and 32,000 years old from the Pintwater Range (Clark County). Bighorn fossils have also been in found most other counties statewide. Based on these paleontological records and keen understanding of bighorn habitat, terrain, and resource needs, NDOW conducted GIS analyses of all Nevada mountain ranges and estimated that historically Nevada was home to over 30,000 bighorn sheep. In fact, they may have been the most abundant native ungulate in Nevada up through the early 1800s.

Alta Toquima is a way cool piece of bighorn history at 11,500 feet on top of the Toquima Range. Archeologist, Dr. David Hurst Thomas with the American Museum of Natural History discovered that Native Americans 2,000 to 600 years ago trekked up from the valley floor to live in a high-mountain summer encampment and hunt bighorn sheep and marmots. We continue to have folks out and about discover more clues to the bighorn sheep history in Nevada. A spelunker back in 2017 found a shaft near ground level that dropped 20 feet into a large cave in Eureka County (“Drop Cave”). BLM state archeologist, Dr. Bryan Hockett repelled down with a team and discovered 3 bighorn carcasses among other wildlife species. The preserved skull of one ewe dated back to 1875. Bones from 2 other bighorn ewes were dated to 1955. This was amazing, since it was assumed that bighorn in this part of the state had already been extirpated and this site was never identified as historic bighorn range. History rewritten! An older couple was walking along the shoreline of Walker Lake last summer and found a portion of an bighorn ram skull partially buried in rock and sand. We again shared it with Bryan Hockett and a few months ago, he returned the skull - 800-900 years old.

John C Fremont (1834) and other explorers, trappers, and mountain men observed bighorn from a distance as they travelled across Nevada along the Humboldt and Truckee River corridors. Similar tales and passages written in their journals read - “several flocks of mountain sheep were seen but we did not succeed in killing any”.

Domestic sheep were first trailed and grazed through Nevada in the 1840s. From 1875 through the 1950s it was estimated that between 500,000 to over 3 million domestic sheep were annually grazing in Nevada over the northern two thirds of the state from valley bottoms to the top of every mountain range. Not only were range/habitat conditions severely impacted, but likely the worst impact was pathogen transmission from domestic sheep interacting with bighorn sheep . During this 75-year period overhunting also reduced herd numbers. But it was the deadly pathogens transmitted to bighorn sheep with naïve immune systems and highly social behavior that caused the extirpation of the entire northern half of Nevada’s bighorn herds. By 1960, it was estimated that only 2,500 bighorn were left in southern Nevada and a few scattered herds in central and western Nevada where desert environments were too severe for domestic sheep grazing.

The last sighting of bighorn in the Ruby Mountains was 1921 and in Jackson Mountains on King Lear Peak was 1946. An interesting account written in 1985 from Elwin Robison speaks about his grandfather who told him that in the late 1800s “mountain” sheep were plentiful in the South Snake Range. Elwin’s own last sighting of mountain sheep was below Pilot Knob (now Windy Peak), of 1 mature ram, 3 ewes, and 1 lamb in 1972! This was 25 years after the presumed time bighorn were extirpated from there.

Nevada’s bighorn sheep restoration efforts that started in the 1960’s was second to none. An incredible synergy and success story of energetic and visionary biologists, sportsmen, and land managers. From 1968 – 2022, we have translocated 3,424 bighorn sheep in Nevada, the most of any other state. In concert with a super productive water development program that has built 210 bighorn guzzlers, Nevada bighorn population steadily grew to 5,200 in 1990, and in 2019 peaked at 12,500, more than any other state. Since the first ram season in 1952, NDOW has issued 11,383 tags with 8,747 rams harvested. Then in 2020, much of the state was hit with a nasty multi-year drought. This was on top of the persistent disease and dieoffs to several herds. Instead of just domestic sheep being pathogen carriers, infected bighorn herds began infecting healthy herds. This was due to the success of past reintroductions that created greater connectivity among adjacent herdsthat were part of bighorn “metapopulations”. Disease and drought along with other ancillary factors we can’t ignore, resulted in the largest decline in Nevada’s bighorn population since the beginning of our restoration efforts. The 2023 statewide estimate of just over 9,000 is almost 30% below our high estimate in 2019. Bearer of bad news. Some herds will recover and grow, from the tremendous moisture from last year’s late summer through this spring. There is hope, but we must move forward with lessons learned and with rekindled energy and vison. We already have started work to help moderate future drought impacts. We have a new tool in our toolbox to deal with dieoffs after they occur, but we need better strategies and actions to prevent them from happening. Nevada has the greatest team of bighorn conservation groups and sportsmen in the west. We need to work together to help our struggling herds get back on their feet and work harder to secure future restoration opportunities. If you are not already a member of a bighorn conservation group in Nevada, consider doing it! Bighorn need your help!

We need to work together to help our struggling herds get back on their feet and work harder to secure future restoration opportunities