State Biologists and UNR Researchers Investigate Decade-Long Mystery of Elk Deaths in Northern Nevada

ELKO, NV — Wildlife biologists and academic researchers across Nevada are working to unravel a decade-long ecological puzzle, conducting intensive field investigations into a fatal condition known informally as seasonal elk mortality syndrome.

The phenomenon has plagued herds across northeastern Nevada, killing between 10% and 30% of GPS-collared female elk during the late spring and early summer in the hardest-hit ranges.

Led by scientists from the University of Nevada, Reno (UNR), the Nevada Department of Wildlife (NDOW), and the U.S. Geological Survey (USGS), the research team is analyzing whether chronic trace-mineral deficiencies are triggering fatal cardiac failures in seemingly healthy animals.

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|       SEASONAL ELK MORTALITY SYNDROME DOSSIER          |
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|  - Investigating Entities: UNR, NDOW & USGS Cooperative|
|    Fish and Wildlife Research Unit                     |
|  - Project Lead: Brian Folt (USGS / UNR Faculty)       |
|  - Lead Field Researcher: Ava Window (UNR)             |
|  - State Partner: Cody McKee (NDOW Staff Specialist)   |
|  - Primary Affected Ranges: Independence, Tuscarora &  |
|    Bull Run Mountains (North of Elko, NV)              |
|  - Mortality Rate: 10% to 30% of Collared Female Elk   |
|  - Mortality Window: Late Spring to Early Summer       |
|  - Clinical Hallmarks: Severe Copper Deficiency, Heart |
|    Lesions, Fluid in Pericardial Sac & Chest Cavity    |
|  - Study Horizon: Multi-Year Study Funded Through 2027 |
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Spring Mortality Defies Normal Survival Patterns

What confounds wildlife managers is the seasonal timing of the die-offs.

While big-game mortality typically peaks during harsh winter months due to starvation or severe cold, these elk die during late spring—the peak season for high-protein green forage, calving, and antler growth.

Field necropsies conducted on deceased cows reveal that the animals are not starving or emaciated.

Instead, they succumb suddenly to cardiovascular collapse.

Pathologists have consistently documented myocardial necrosis, cardiac lesions, elevated pre-death body temperatures, and excessive fluid accumulation ballooning around the pericardial sac and inside the thoracic cavity.

The Copper Deficiency Hypothesis

Tissue biopsies from carcasses have repeatedly identified low levels of copper, an essential trace mineral required for tissue elasticity, cellular function, and immune defense.

Researchers are conducting soil, water, and forage sampling across the Bull Run, Independence, and Tuscarora mountain ranges north of Elko to determine whether the Great Basin landscape naturally lacks copper or if competing minerals (such as molybdenum or iron) are blocking dietary absorption.

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|             RESEARCH PATHWAYS & TESTING PHASES         |
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|  • Immune Vulnerability: Mineral imbalances may render |
|    elk unable to survive common pathogens or parasites |
|  • Geographic Scope: GPS telemetry and ear-tag data   |
|    show the syndrome may extend beyond Elko County     |
|  • Decision Horizon: Field data collection is funded   |
|    through fall 2027 to guide state management rules   |
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“Usually in the spring, elk do quite well here and have extremely high survival,” said Brian Folt, a USGS scientist and UNR natural resources faculty member who leads the research project. “We’re beginning to see that this problem may occur in other areas as well. We hope our results will directly inform wildlife management decisions and help protect Nevada’s elk.”

NDOW staff specialist Cody McKee noted that systemic copper deficiency could act as an underlying multiplier, transforming minor environmental stressors, mild illnesses, or typical seasonal parasites into lethal events.

Field teams are tracking solar ear-tagged and collared elk across northeastern Nevada through the current seasonal transition.

Source: University of Nevada, Reno College of Agriculture, Biotechnology & Natural Resources; Nevada Department of Wildlife Research Division; U.S. Geological Survey.