Pedigree‐based genetic management improves bison conservation

Overhunting and widespread land use change nearly caused the extinction of North American bison (Bison bison) by the late 1800s. Recovery efforts focused on preserving the remaining individuals and establishing federally managed conservation herds to build more sustainable populations. Today, bison in conservation herds are maintained in small, isolated herds that are managed through an annual or biannual cull of individuals to maintain target population sizes. We assessed alternative culling strategies for maintaining genetic variation over the long term in managed wild bison herds. Our objective was to compare a strategy modeled after a United States Fish and Wildlife Service strategy (all‐allele conservation culling strategy [AAC]) to a pedigree‐based mean kinship strategy (MK) and to a Random strategy that does not incorporate genetic data and is used to manage some conservation herds. We built an individual‐based model, parameterized in accordance with bison biology, to compare these culling strategies in 2 federally managed conservation herds at the Fort Niobrara National Wildlife Refuge (FTN herd) and the National Bison Range (NBR herd). Our MK strategy retained more genetic variation and slowed the accumulation of inbreeding relative to the AAC or Random strategies, and these findings were consistent across wild bison herds with different founding sizes and current genetic diversity. These findings extend previous work demonstrating the utility of pedigree‐based management strategies in captive and wild population management, and show that such strategies maximize the retention of genome‐wide variation in contemporary bison herds. The modeling approach used in this study was useful for assessing outcomes prior to implementation, and the specific models developed for this study can be easily adapted to other managed wildlife species. © 2018 The Wildlife Society.