March 21, 2014: Possible Results of the 3/18 FWP/DOL/BOL Proposal for
Yellowstone Bison – James A. Bailey
Current situation: There are about 4000 bison in the Yellowstone ecosystem –
about 1200 in the central herd and 2800 in the northern herd. There is some
genetic exchange between these herds. A few males from the northern herd visit
and presumably breed with the central herd each year, returning to the northern
herd after the rut. Animals from the central herd, probably mostly calves and
yearlings, join the northern herd each winter. (This may be in large part due to
social disruption from population control activities.) This degree of separation of
the 2 herds (breeding populations) creates concern for the genetic health of, in
particular, the smaller central herd. In a smaller, more isolated herd, there is a
greater potential for genetic drift (random factors) to replace natural selection,
jeopardizing fitness of bison. There is also a greater rate of loss of alleles to
genetic drift. Likely, the central herd is already losing more than 5% of its
alleles each 100 years. In addition, smaller herds have a greater stochastic
risk – the probability that unusual and unpredicted events will eliminate or
seriously reduce the herd. Disease, including chronic wasting disease, is one
of those risks.
There are no wild bison, year-round, in Montana. Our only wild bison are those
allowed to visit us, briefly, from the Park each winter/spring. In the 2005 IBMP
EIS and decision, the Park Service agreed to cooperate in reducing and
maintaining a Yellowstone herd of 3000-3500 bison. This agreement assumed
no bison outside the Park after May 15 each year. It has been outdated by new
research of bison genetics and Brucella transmission.
FWP/DOL/BOL propose to relate amounts of tolerance for bison outside the Park
to reducing the total herd, inside and outside the Park. The more bison outside
the Park in Montana, the fewer there may be in the Park. Tolerance of bison in
Montana could mean that bison will prolong their temporary visits to the state
each year. Or, bison could establish year-round populations in our state; but this
might not occur for years. Ultimately, Montana could have both a permanent
bison herd and a migratory herd that visits Montana each winter/spring.
Scenario 1: For as long as these bison choose to return to the Park each year,
Montana will continue to have no permanent wild population of bison
(unless a bison herd is established elsewhere, which will not happen soon and
may never happen). There will be no increase in bison available to Montana
hunters, who hunt in fall and early winter. For tribal hunters, who hunt in late
winter as well as earlier, bison may be available over a wider area, but it is likely
that much harvest of bison will continue to occur near the Park boundaries.
Total numbers of bison may be reduced, in exchange for a small benefit
from some bison staying longer in Montana each spring.
The following scenarios involve reductions of the bison herd. I am arbitrarily
assuming stable proportions of bison in reduced central and northern herds (30%
in the central herd, 70% in the northern herd, as today). However, with recent
herd reductions, the central herd has been declining and the northern herd has
increased. Removals of bison from the northern herd have occurred at the
northern boundary; whereas removals from the central herd have occurred at
both the northern and western boundaries. Thus, the proportion of Park bison in
the central herd may actually decline. If this happens, negative impacts to the
central herd are underestimated here.
Scenario 2: Hold, reduce herd to 3700-4000*. At this herd size, up to 200
bison will be allowed in area E, Horse Butte peninsula and adjacent land
connecting it to the Park on the east. FWP/DOL would continue efforts to
reduce the overall herd to 3000. With a herd size of 3700, there would be
200 bison in area E, 1050 bison in the central herd, and 2450 bison in the
northern herd. If 200 bison remain to breed (August) in area E, this will be
an inbred herd with a rapid loss of alleles to genetic drift. This threat to their
genetic health would be ameliorated somewhat if any migrating bison from the
Park survive and join the Horse Butte herd long enough to breed. There is no
assurance that bison would be exchanged between the Horse Butte herd and the
central herd. There would be a 12.5% reduction of the 2 Park herds, the only
near-wild bison herds south of central Canada. In particular, there would
be increased losses of fitness and alleles due to genetic drift in the central
herd. If, due to changing Park Service policies or weather conditions affecting
exposure of bison to hunting or other removals, the overall herd regrows to
exceed 4000, a migrating or established permanent herd of bison in area E
would no longer be tolerated and would be removed by May 15.
Scenario 3: Reduce herd to 3300-3700*. At this herd size, bison would be
allowed to leave area E (Horse Butte) toward the north into area C (which
includes area E). FWP/DOL would continue efforts to reduce the overall
herd to 3000. The number of bison allowed in area C is unspecified. However,
the more bison in area C, the fewer bison would be allowed within the 2 Park
herds. If we assume that there were 400 bison in area C (200 in area E and
200 northward), with an overall herd size of 3300, there would 870 bison in
the central herd, and 2030 bison in the northern herd. If bison stay in area C
year-round, it is likely they would form only 1 breeding population. Having 400
bison in area C would avoid significant inbreeding, but these animals
would rapidly lose alleles due to genetic drift. There is no assurance that
bison would be exchanged between area C and the central herd to ameliorate
this problem of genetic health. There would be a 27.5% reduction of the 2
Park herds. At this level, it is reasonable that the northern herd would lose
alleles at a rate near 5% per 100 years, and that the central herd would lose
alleles even more rapidly. If more than 400 bison are allowed in Montana, the
FWP/DOL/BOL document demands an even larger reduction of the Park herds.
If, due to changing policies or weather conditions, the overall herd regrows to
exceed 3700 animals, bison would no longer be tolerated in most of area C
(perhaps only in area E, as above).
Scenario 4: Reduce herd to <3300*. (Under the outdated 2005 IBMP
agreement, the Park Service is not obligated to cooperate in reducing the
Yellowstone bison herd to this level.) At this herd size, bison would be allowed in
all of area B (which includes areas C, E and more). Allowing bison year-round in
area B, with no population-size triggers, was the preferred alternative in the
original EA. FWP/DOL would continue efforts to reduce the overall herd to
3000. The number of bison allowed in area B is unspecified. But more bison in
area B requires equally fewer bison in the 2 Park herds. If we assume there
were 600 bison in area B with an overall herd size of 3000, there would be
720 bison in the central herd and 1680 bison in the northern herd. If all 600
bison stay in Montana year-round, they might form 2 separate breeding
populations (with one south of Hebgen Lake and the Madison River). Likely, one
of these Montana herds would be subject to significant inbreeding and
both would have significantly rapid loss of alleles to genetic drift. There is
no assurance that bison would be exchanged between these breeding
populations, or with the central herd, to ameliorate this problem of genetic health.
There would be a 40% reduction of the 2 Park herds. At this level both Park
herds likely would lose alleles at rates exceeding 5% per 100 years. The
central herd would be especially vulnerable. If, due to changing policies or
weather, the overall herd regrows to exceed 3300, bison would be exterminated
in some parts of area B.
Scenario 5: Bison in the Taylor Fork area. The Taylor Fork is a small part of
area B, and within the Gallatin River drainage. With an overall bison herd of
<3300*, 100 bison would initially be allowed in the Taylor Fork area.
Intentional transplanting of bison to this area is not planned. Bison may not find
the area for years or decades. However, if there were 100 bison in the Taylor
Fork area, other bison herds, in or outside the Park would be reduced by
100. Given the distance, habitat and drainage divide, it is most likely that any
year-round herd of bison in the Taylor Fork area would be a separate
breeding population, subject to extreme inbreeding and genetic drift.
* All the above population triggers could be reduced by the BOL at its May
meeting.
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Overall, this proposal is a conservation geneticist’s nightmare. We have the
most important conservation herd, the only truly wild herd, of bison south of
Canada. Its size and segregation make its future genetic health questionable,
especially the smaller, central herd. This proposal would fragment the herd
into as many as 5 subherds, with interchange of bison unlikely for the proposed
Taylor Fork herd, reduced for the 2 Park herds, and uncertain for 2 possible new
herds in Montana. (I assume that exchange of bison between the northern and
central herds in the Park would decline simply because there would be fewer
animals in each herd. Exchanges of animals with and between the 2 new herds
in Montana would be inhibited by continued harvesting, administrative killing, and
trapping/slaughter of animals.)
The FWP/DOL/BOL proposal ignores these issues of conservation
genetics/biology. It ignores the existing questionable status of the Park’s central
herd. It ignores the Park Service mandate to maintain an unimpaired bison
genome for the benefit of future generations of us.
The FWP/DOL/BOL proposal demands Park Service acquiescence to and
participation in achieving its narrow and short-sighted goals. (Continued trapping
and removal of bison at the Park’s Stevens Creek facility is assumed.) Yet the
proposal has not been formally submitted to the Park Service for advice or
consent.
Our legislature has ordained that, in Montana, Yellowstone bison will be
managed by DOL/BOL, not by FWP. Now DOL/BOL presume to manage federal
bison in another state!
What could Montana gain from this proposal? We might have, at most, 3 small
bison herds, at least 2 with inbreeding and all with serious loss of alleles and
fitness due to genetic drift. Likely, we will have few bison because the Park will
have to retain most of its bison to fulfill its federal mandate. (The current
state/federal agreement, resulting from a Montana lawsuit against the Park, is for
3000-3500 bison. This outdated goal is not supported by recent science.
Rather than recognizing the science or the Park Service unimpairment mandate,
the FWP/DOL/BOL proposal aims for the rock-bottom number of 3000 bison.)
For harvest, these small Montana herds would, at most, provide 50-60
animals/year on a sustained basis. Many of these may be taken by tribal
members. Few Montana hunters would benefit.
If the FWP/DOL/BOL proposal succeeds in causing a significant reduction of the
Park bison herds, there would be fewer bison leaving the Park in many winters.
This is touted to benefit cattle producers as a reduced risk of Brucella
transmission. However, almost all the risk of brucellosis to cattle is from elk, not
from bison. There are very few cattle producers affected by bison coming out of
the Park and no Brucella transmission from bison has occurred. This touted
benefit is a sham.
The original EA provided an opportunity to move forward with bison conservation
and management to benefit most Montanans. However, the current
FWP/DOL/BOL proposal adds specified population triggers and other stipulations
that make these benefits unlikely, at best. The EA contained no analysis of
effects upon population genetics of Yellowstone bison, in or out of the Park.
Differences between the EA and the FWP/DOL/BOL proposal are significant and
may make adoption of the proposal into a violation of the Montana Environmental
Protection Act in that the new proposed alternative was not analyzed, using
current knowledge and science, in the original EA (or in the 2005 EIS
establishing the IBMP).
Montana could seize the opportunity to have and benefit from some managed
bison in Montana. The issue for Montanans is not how many bison are in the
Park, in another state. The issue is how many Montana bison do we want and
where do we want them. The issue is how to incrementally learn how to manage
bison issues and how to produce bison benefits for Montanans. We need to stop
persecuting bison, stop persecuting the Park Service for fulfilling its legal
mandate, and proceed with bison conservation and management in Montana for
Montanans.