Assessing consequences of anthropogenic hybridization: Great Lakes mallard movement and resource selection

The release of domesticated animals is resulting in anthropogenic hybridization with their wild congeners and there is concern that these interactions are a risk to conservation. In North America, large-scale releases of domesticated mallards have continued for over a century, yet the potential ecological consequences are not well understood. Towards this, we assessed whether hybridization between game-farm and wild mallards was associated with variation in movement and resource selection behavior, which in turn can affect survival and reproduction.

We coupled genomic, telemetry, and remotely sensed spatial data for 592 female mallards sampled from 2021 to 2023 in the Great Lakes region of North America and tested for association between an individual's level of domestic ancestry, their local and migratory movement, and resource selection during the non-breeding period. We used linear mixed models and general linear models to examine factors affecting daily movement distance and autumn migration probability, respectively. We implemented a step-selection function and conditional logistic regression to estimate relative selection strength of land cover types relevant to mallard resource use.

We recovered 44% of GPS-marked birds as genetically wild, with the remaining 56% being feral game-farm or wild × game-farm mallard hybrids. Increased domestic ancestry was associated with shorter daily movement distances, decreased likelihood of migration, and higher selection for urban developed land cover.

Lower mobility and selection of urban areas by individuals with greater domestic ancestry warrant further investigation as factors potentially affecting survival and reproduction.