American Bison - Buffalo Field Campaign

Plate 7.3 Male plains bison sparring. Photo: Dwight Lutsey.
control areas) may be applied for infected wild populations in
large wilderness areas. The presence of reportable diseases may
preclude translocations. Management interventions are possible
to control some diseases (anthrax, BVD, JD). Reportable
diseases were present in 5 of 62 (8%) of plains bison herds and
3 of 11 (27%) wood bison herds.
7.8 Cattle Gene Introgression
The molecular legacy of historic hybridisation between bison
and cattle is a serious challenge for bison conservation
today (Halbert and Derr 2007). Forced hybridisation has
left a legacy of cattle DNA that is
widespread among contemporary
bison populations (Chapter 4). The
implications for bison conservation are
just beginning to be understood and
appropriate interventions considered.
Available technology allows testing
of populations for the presence of
markers for the cattle genome and
mitochondrial DNA (MtDNA), but all
conservations herds have not yet
been tested (Figure 7.7). Among those
tested, introgression was demonstrated
in seven plains bison conservation
herds, but none of eight wood bison
herds. Based on stocking sources,
introgression is likely in 17 plains bison
herds and no wood bison herds.
Figure 7.7 Results of tests for cattle gene
introgression in conservation herds.
7.9 Conclusions
Originally, the American bison ranged from
northern Mexico to Alaska. Plains bison
occurred from Northern Mexico to central
Alberta and wood bison occurred from central
Alberta to Alaska. The continental population
underwent a dramatic decline during the
19th century, caused by overhunting, but has
since partially recovered. Approximately 93%
of the continental population is managed for
private commercial propagation; very few of
these herds are managed primarily for species
conservation, and none are managed in the
public interest for conservation. Bison currently
occupy less than 1% of their original range,
and conservation herds occupy a small fraction
of that 1%. The number of conservation herds
has increased since 1930, but the numbers of
individuals in populations managed primarily for conservation
has changed little since then. There are 62 plains bison and
11 wood bison conservation herds (managed for conservation
in the public interest). Conservation herds are typically small
(fewer than 400 animals) and populations are widely dispersed
with only one situation that provides geographic conditions
for natural movements between population units. The current
number of large populations is five plains bison and three wood
bison herds. The estimated number of breeding females in
conservation populations is 9,227 plains bison and 4,892 wood
bison. Their current range is restricted by land use and wildlife
American Bison: Status Survey and Conservation Guidelines 2010 61