EL PASO, Texas (Nov. 4, 2026) – Researchers have long known that releasing domesticated ducks can alter wild populations. Now, a study led by a doctoral student at The University of Texas at El Paso has documented, for the first time in North America, when and where these genetic changes took place and tied them directly to more than a century of releases.
"For decades, we could see that domestic ancestry existed in wild mallards, but we did not have a clear record of how it got there," said Lauren McFarland, a doctoral student in ecology and evolutionary biology in the UTEP College of Science and corresponding author of the study. "By looking back through time, we were able to connect changes in the birds' DNA to the history of human releases. That gives wildlife managers a new way to evaluate what these practices mean for wild populations."
The findings , published in the journal Current Biology, also carry a warning about the birds' genetic health, the team said. Mallards with more game-farm ancestry, or domestication, were less genetically diverse and more inbred. Captive game-farm mallards carried about 35% less genetic diversity than wild mallards and more than twice their level of inbreeding.
Genetic diversity is what allows wild populations to adapt to disease and changing environments. The authors note that interbreeding with domestic stocks can erode local adaptations and increase the burden of harmful genetic variants in wild populations. They also raise the possibility that the low diversity of game-farm birds weakens their immune defenses, a concern while avian influenza circulates among wild and domestic birds.
The research reconstructs the genetic history of North American mallards from 1800 to 2020 by examining genetic data from more than 400 historical museum specimens and over 600 contemporary mallards. It reveals how large-scale releases of domesticated ducks raised for hunting have changed the ancestry of wild mallards, particularly in eastern North America.
Such releases, known as stocking, are commonly intended to supplement wildlife populations.
The work was completed by scientists at UTEP, the Smithsonian Institution, West Texas A&M University and the State University of New York College of Environmental Science and Forestry. McFarland led the work under the supervision of Philip Lavretsky, Ph.D., associate professor in the UTEP Department of Biological Sciences, one of the nation's leading researchers in duck conservation genetics, and a co-author of the study.
The samples McFarland examined spanned North America's four major migratory flyways, allowing the team to compare regions with different histories of releasing captive-bred ducks.
The researchers found the first signs of game-farm mallard ancestry in wild ducks during the 1910s and 1920s, around the time documented releases began. Rather than building gradually, this ancestry entered wild populations in repeated waves that reflected regional stocking practices.
The effects were far from uniform. Mallards in the Pacific and Central flyways retained largely wild genetic ancestry. In the Atlantic Flyway and parts of the Mississippi Flyway, especially the Great Lakes and northeastern United States, domestic ancestry became much more prevalent. Since the 1980s, mallards sampled in the Atlantic Flyway have averaged about 20% game-farm ancestry.
"This research demonstrates how scientific discovery can inform decisions well beyond the laboratory," said Marc Knecht, Ph.D., dean of UTEP's College of Science. "Lauren's leadership in a study of this scale is an outstanding example of the scholarship emerging from our graduate programs, with implications for wildlife conservation across North America and beyond."
About The University of Texas at El Paso
The University of Texas at El Paso is America's leading Hispanic-serving university. Located at the westernmost tip of Texas, where three states and two countries converge along the Rio Grande, 84% of our 27,000 students are Hispanic, and more than half are the first in their families to go to college. With respect to research, UTEP is in the top 5% of universities in America and offers 170 bachelor's, master's and doctoral degree programs at the only open-access, top-tier research university in America.
