Download Item 38C Bobcat Trapping Ban Implications - CAL

Ecological Implications of the
Bobcat Trapping Ban:
A Summary View of the Impact on Endangered/Vulnerable Species
Josh P. Brones
Government Affairs Coordinator, Sportsmen’s Alliance
Policy Liaison, Al Taucher Conservation Coalition
Introduction
 Bobcats fulfill an important role in the
ecosystem.
 Bobcats directly and indirectly
influence and interact with numerous
species of flora and fauna.
 Consideration of a potential ban on
trapping must consider the ripple
effects this action might have on other
species.
Species of Concern
Fisher

The fisher (Pekania pennanti) is an semi-arboreal member of the weasel family found in two evolutionarily
significant units ("ESU's") in Northern California and the Southern Central Sierra Nevada mountains.

Timeline:

2008: Center for Biological Diversity ("CBD") petitioned the Commission to list the fisher (formerly known as
Pacific fisher (Martes pennant)), as threatened or endangered under the California Endangered Species Act
("CESA").

2010: Commission determined that listing the fisher was not warranted and CBD filed suit in court to
overturn the decision.

2012: Commission met in executive session and, pursuant to court order, voted to set aside its
previous findings rejecting the petition and directed the Department to prepare a status review for
consideration.

2015: Commission voted to list the fisher population found in the southern ESU per the
recommendation of the Department. The fact that the Commission would vote to list the fisher is not
unsupported, and is consistent with the steps the United States Fish and Wildlife Service is taking to
federally list the fisher under the Endangered Species Act.

However, the two actions the Commission took in August 2015 are at odds with each other given the existence
of several undisputed facts.
Ecological Implications
 Predation is the largest cause of fisher mortality,
and bobcats are the largest source of predation.
 60% killed by bobcats…nearly
twice as much as next
predator.
 Felids are responsible for more
than 80% of all predation
deaths.
 Predation accounts for 73% of
female mortality and 45% of
male mortality.
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5
5

1. Wengert, G. Trends in Fisher Predation in California. 2011

5. Spencer, W., et al. Southern Sierra Nevada fisher conservation assessment. 2015
Ecological Implications, cont.
 Bobcats prey predominantly on female fishers.
 “Most female fishers killed by bobcats.”
 “Bobcats killed only female fishers.”
 “All bobcat kills have been female.”
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2
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1. Wengert, G. Trends in Fisher Predation in California. 2011.
2. Wengert, G. Ecology of intraguild predation on fishers (Martes pennanti) in California. 2013.
3. Sweitzer, R. and Barrett, R. SNAMP Fisher Study: Sources of Mortality. 2009
Ecological Implications, cont.
 Bobcat predation on female fishers occurs most
heavily during the period when fishers have
dependent young.
 Three females had seven kits.
 One study found female carcass on
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ground with bobcat in den tree with
kit in its mouth.
 Over 70% of bobcat-related deaths
occurred during period of rearing.
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3. Sweitzer, R. and Barrett, R. SNAMP Fisher Study: Sources of Mortality. 2009
5. Spencer, W., et al. Southern Sierra Nevada fisher conservation assessment. 2015
6. Bohnam, C. DFW Status Review Pacific Fisher. 2015
Ecological Implications, cont.
 Predation can be an impediment, if not a barrier, to
the increase in population and distribution of a
species, and materially impairs the successful
translocation of a species to another area where
predation exists.
 “even modest increases in mortality rates(10-20%) could
prevent population expansion”
 “…the ability of the species to establish a self sustaining
population is affected by predation from its primary
predator, the bobcat”
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1. Wengert, G. Trends in Fisher Predation in California. 2011
4. Halsey, S. Modeling predator habitat to enhance reintroduction planning. ​2015.
Trapping Implications
 Trapping is the most effective means of mitigating the bobcat’s
impairment to fisher recovery.
 Trapping represents the largest source of take of bobcats (73% of total)
 Kern County (located within the Southern Sierra Nevada ESU) represents
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the single largest region of trapping take.7
 144 in 2014-2015 season was 33% more than second largest source.
 Trapping does not impact or harm emerging or stable fisher populations.
 Trapping is the only practical means of selecting for the sex of the bobcats
taken (and removed from population.)
 It is suggested that the use of trapping records be used to determine if the
bobcat population is increasing.1
1. Wengert, G. Trends in Fisher Predation in California. 2011
7. Garcia J. Bobcat Harvest Assessment 2014-2015. 2015
Implications Summary
 These cumulative effects threaten sustainable fisher
population levels, recovery, and successful
translocation.
 Makes the banning of bobcat trapping without scientific due
diligence antithetical to the CESA listing of the fisher
 Creates challenges to fulfilling the purpose of the listing to
maintain and increase population and distribution.
 It was therefore inherently at odds for the Commission to take
the action to list one of the state's two fisher populations while
at the same time banning the most effective and popular
method of controlling the single greatest threat to that fisher
population.
Works Cited
 1. Wengert, G. Trends in Fisher Predation in California. 2011.
 2. Wengert, G. Ecology of intraguild predation on fishers
(Martes pennanti) in California. 2013.
 3. Sweitzer, R. and Barrett, R.
SNAMP Fisher Study: Sources of Mortality. 2009
 4. Halsey, S. Modeling predator habitat to enhance reintroduction
planning. ​2015.
 5. Spencer, W., et al. Southern Sierra Nevada fisher
conservation assessment. 2015
 6. Bohnam, C. DFW Status Review Pacific Fisher. 2015
 7. Garcia J. Bobcat Harvest Assessment 2014-2015. 2015