American Bison - Buffalo Field Campaign

and foothills. Bison have a profound influence on ecosystems
and create habitat heterogeneity through various means. As
primarily graminoid (grasses and sedges) eaters, variable grazing
pressure by free-ranging bison and their interaction with fire
create habitat patchiness on which grassland bird diversity
depends. Wallowing behaviour further promotes heterogeneity
by forming temporary pools and changing surface hydrology and
runoff and creating local patches of disturbed soil in which some
flowering plant species prosper. Bison are dispersers of seeds,
and are sources and redistributors of nutrients for predators,
scavengers, plants, and ecosystem processes. Gogan et al.
describe foraging patterns and habitat use by wood and plains
bison in various ecoregions, from the arid southwest to humid
cold boreal regions. The authors also review bison population
structure and reproduction and demonstrate that under natural
conditions newly established bison populations can double
every four to six years. Population numbers are affected by both
density-independent events, such as severe winters and wild
fires, and density-dependent factors such as disease and wolf
predation. While humans were a bison predator for thousands of
years, the advent of firearms greatly increased human predation,
so that by the mid-1800s, an estimated 500,000 plains bison
were killed annually for subsistence and 100,000 for hides. The
human-firearm-commerce combination, it would seem, largely
voided the density-dependent relationship between bison and
human predation until it was almost too late for the American
bison.
In Chapter 7, C. Gates and co-authors assess the status of
conservation herds using seven criteria: numerical status,
geographic status, population size and class distribution,
opportunity for mate competition among mature males, presence
of wolves, presence of diseases that could affect conservation
status, and occurrence or likely occurrence of cattle-gene
introgression. The designation “conservation herd” is assigned
to herds managed by federal or state/provincial governments
or non-governmental organisations (NGOs) whose mission
is nature conservation. Remarkably, little progress has been
made in recent decades in increasing the number of animals
in conservation herds. From the few hundred that remained in
the late 1800s, the number of animals in conservation herds
increased in the first half of the 1900s, but then levelled off, or
in the case of the wood bison, even declined, while the number
of conservation herds has continued to grow to the present
day. As of 2008, there were 62 plains bison conservation herds
containing about 20,500 animals, and 11 conservation herds
of wood bison containing nearly 11,000 animals. Meanwhile,
starting in the 1980s, the commercial bison industry prospered
with the total population growing to around 400,000 animals
in 2007, roughly evenly divided between the U.S. and Canada.
Although a few conservation herds exceed 1,000 animals, most
conservation herds of both wood and plains bison have fewer
than 400 animals and, in the case of the plains bison, many
are fenced in areas of only a few thousands hectares and not
subject to natural predation. Until recently, there was a wild
bison herd inhabiting a trans-boundary area between Mexico
and the U.S., the only herd meriting conservation status in
Mexico. But now, it has been restricted to a private ranch on
the U.S. side. The American bison nearly qualifies for listing as
Vulnerable Ca2(1) under IUCN criteria and is currently listed as
Near Threatened on the IUCN Red List.
As K. Aune and co-authors describe in Chapter 8, bison
conservation must deal with a complex maze of legal and
policy issues. Much of this complexity is due to a history of
bison being treated like livestock. As the authors note, “During
the great restoration period of wildlife management, bison
were routinely classified and managed by state/provincial and
federal agencies across North America as a form of livestock,
while other wildlife were classed and managed as free-roaming
wild animals.” They subsequently provide a detailed review of
the legal status of, and conservation initiatives underway for,
bison in Mexico, the U.S., and Canada. The legal recognition
of bison as wildlife or livestock, or both, varies across various
federal, state, and provincial jurisdictions in North America. For
example, only ten U.S. states, four Canadian provinces and
two territories, and one Mexican state classify bison as wildlife;
all other states and provinces within the bison’s historic range
designate them as domestic livestock. Overlaying this legal
map for bison are several stakeholder groups that manage
bison: public wildlife and land management agencies, Native
American groups, non-profit conservation organisations, and
private producers. Reportable diseases present another set
of legal issues that affect international and interstate transport
of bison. Aune et al. suggest that a paradigm shift is required
whereby the public recognises bison as wildlife, and that there
is much greater social tolerance, especially in the agricultural
community, if major progress is to be made in re-establishing
free-ranging bison on their native range. Moreover, large-scale
restoration over big landscapes will typically require partnerships
and co-management among multiple landowners and resource
managers, and more enlightened and coordinated government
regulations and policies.
In Chapter 9, J.E. Gross and co-authors provide guidelines
for population, genetic, and disease management for both
existing conservation herds and for the full recovery of bison
over both the short and long term. As the authors explain,
conservation focuses on retaining existing ecological, cultural,
and genetic characteristics of bison, whereas full recovery
entails a broader vision of bison inhabiting landscapes that
permit the full expression of natural behaviours and ecosystem
interactions that once existed. The guidelines first address bison
behaviour, particularly the importance of ensuring natural mating
systems that involve avoiding a skewed sex ratio and allowing
American Bison: Status Survey and Conservation Guidelines 2010 xvii