Delaney P. Boyd, Conservation of North American Bison: Status and
Recommendations, April 2003.
"Modern conservation of many species is often based on the goal of ensuring long-term
persistence and ecological adaptation of viable populations in the wild (Soule 1987a;
Secretariat of the Convention on Biological Diversity 1992; IUCN/SSC 2002; IUCN
2003a). Viability relates to the capacity of a population to maintain itself without
significant demographic or genetic manipulation for the forseeable ecological future
(Soule 1987a). Natural selection, diverse genetic composition, and population regulating
factors (e.g., predation) contribute to the maintenance of the wild character of a species,
and the traits that enable an animal to survive in a natural setting with minimum human
interference (Knowles et al. 1998). Given these parameters, 'wild' bison would be nondomesticated, subject to evolutionary adaptation through natural selection, and normally
reside in free-ranging, naturally-regulated herds within original bison range. However,
this survey demonstrates that most herds are confined by fences or socio-political forces
in habitats of varying sizes, sometimes outside of original range, and are subject to
varying levels of management intervention by humans. Although the ideal goal of bison
conservation is to maintain the bison as a wild species, in contrast to the domesticated
state, the realities of the developed landscape and existing human settlement limit
opportunities for conserving bison under completely natural conditions." (Pages 1-2)
"The bison is a land-intensive nomadic species that once roamed over great distances
on the North American landscape. Large-bodied animals are especially vulnerable to
the effects of habitat fragmentation because they require a large amount of suitable
habitat (Berger and Cunningham 1994). Fragmented populations can be more
susceptible to inbreeding pressures, loss of genetic diversity, and extinction (Berger and
Cunningham 1994; Mace et al. 2001). On the continental scale, natural habitats have
been reduced to a fraction of their historical extent (Mace et al. 2001). Human
population growth and development have led to the appropriation of extensive areas of
land within original bison range for natural resource extraction, agriculture, ranching of
both cattle and commercial bison, and urban and rural settlement (Johnson et al. 1994;
Berger and Cunningham 1994; Mace et al. 2001). These competing land uses constrain
possibilities for preserving or restoring large tracts of habitat for bison recovery."
(Page 49)
“Genetic diversity within a species provides the mechanism for evolutionary change and
adaptation (Mitton and Grant 1984; Allendorf and Leary 1986; Meffe and Carroll 1994;
Chambers 1998). Reduction in genetic diversity can result in reduced fitness,
diminished growth, increased mortality, and reduced evolutionary flexibility of individuals
within a population (Ballou and Ralls 1982; Mitton and Grant 1984; Allendorf and Leary
1986; Berger and Cunningham 1994). There are four interrelated mechanisms that can
reduce genetic diversity: demographic bottlenecks, founder effects, genetic drift, and
inbreeding (Meffe and Carroll 1994). Over the last two centuries, bison in North America
have to some degree experienced all of these mechanisms.” (Page 60)
“The goals of commercial bison production are generally not compatible with the
conservation of the wild species. Further, commercial bison operations could pose a
threat to conservation populations through a form of genetic pollution, if genetically
selected commercial animals are mixed into conservation herds. The most prudent
action is to identify and maintain existing conservation herds, and avoid mixing
commercially propagated stock into those herds. (Page 72)