American Bison - Buffalo Field Campaign

Figure 7.1 Locations and size classes of bison conservation herds in North America. Historic ranges of wood and plains bison were based on
Stephenson et al. (2001) and Sanderson et al. (2008), respectively.
numerical status of bison. Beyond viability, resiliency refers
to the need to preserve individual populations large enough
to have a high probability of persisting for extended periods
in the presence of minimal management, and which preserve
genetic diversity and the potential for adaptation to changing
conditions (minimum of 1,000 bison; Gross and Wang 2005).
Representation reflects the need to preserve populations of
a species across the fullest array of environments in which it
occurred originally. Redundancy refers to the need to preserve a
sufficient number of large populations to safeguard against local
catastrophes.
Here, we provide a summary of the status of wood bison and
plains bison populations managed by national or state/provincial
public governments and non-governmental organisations whose
primary mission is nature conservation. For simplicity, these
populations are referred to as “conservation herds”. Information
on the number of herds and bison under captive commercial
propagation is also included. Display herds in zoos were not
56 American Bison: Status Survey and Conservation Guidelines 2010
enumerated. The following seven criteria were considered for
reviewing the status of conservation herds: numerical status;
geographic status; population size class distribution; opportunity
for mate competition among mature males; presence of
wolves; the presence or absence of diseases that could affect
conservation status (see chapter 5); and presence, or likely
presence, of cattle genes based on analysis or stocking history.
7.2 Numerical Status
Numerical status refers to the number of bison and number
of populations in North America in conservation herds. Where
possible, the reported number of bison in each conservation
herd was verified with herd managers in 2008, but the numbers
reported here may differ from the actual numbers of animals
present because not all herds were surveyed recently, census
techniques may not account for every animal, herds are not
always managed to achieve a consistent target number, and
herd size and productivity vary annually.