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.1 Felids are responsible for more than 80% of all predation deaths.5 Predation accounts for 73% of female mortality and 45% of male mortality.5 1. Wengert, G. Trends in Fisher Predation in California. 2011 5. Spencer, W., et al. Southern Sierra Nevada fisher conservation assessment. 2015 Wengert, G. Trends in Fisher Predation in California. 2011. "Predation ranks as highest cause of mortality" and cause, "60% of all documented fisher mortalities" "60% killed by bobcats" which is nearly twice as much as the next predator Spencer, W., et al. Southern Sierra Nevada fisher conservation assessment. 2015 "Felids are associated with >80% of all known or suspected predation deaths on SNAMP and KRFP from 2007 to March 2013 (N=50) (Wengert 2013). "Across California, predation accounts for 73% of female mortality and 45% of male mortality (Wengert et al. 2014)."

Ecological Implications, cont. Bobcats prey predominantly on female fishers. “Most female fishers killed by bobcats.”1 “Bobcats killed only female fishers.”2 “All bobcat kills have been female.”3 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 Wengert, G. Ecology of intraguild predation on fishers (Martes pennanti) in California. 2013. The abstract indicates, "bobcats killed only female fishers."  Wengert, G. Trends in Fisher Predation in California. 2011. "Most female fishers killed by bobcats" Sweitzer, R. and Barrett, R. SNAMP Fisher Study: Sources of Mortality. 2009 The graph, BASIC RESULTS: Apparent size‐related pattern of predation by different species of carnivores, note that 60% were juvenile females and 40% were adult females.  Spencer, W., et al. Southern Sierra Nevada fisher conservation assessment. 2015 "In the southern Sierra Nevada, bobcats and lions each account for 23% of all mortality, with bobcats killing female fishers and lions mostly responsible for killing males...(Wengert et al. 2014)."

Ecological Implications, cont. Bobcat predation on female fishers occurs most heavily during the period when fishers have dependent young. Three females had seven kits.3 One study found female carcass on ground with bobcat in den tree with kit in its mouth.5 Over 70% of bobcat-related deaths occurred during period of rearing.6 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 6. the Department's summary recommendation (to not list the northern ESU but to list the southern ESU) and their Status Review of the Fisher, they cite that, "Predation risk for females also varied seasonally: over 70% (19 of 25) of female predation deaths by bobcats occurred late March through July, the period when fisher kits are still dependent on their mothers for survival (Highley et al. 2013:35, Wengert et al 2014)." 3. Sweitzer, R. and Barrett, R. SNAMP Fisher Study: Sources of Mortality. 2009 The graph, BASIC MORTALITY RESULTS: Fisher Mortalities by Season, indicates that the overwhelming majority of predation occurs during Spring when fishers are giving birth and rearing young. "All bobcat kills have been female fishers; bobcats detected at 5 different dens." "3 bobcat-killed adult females were reproductive at death (F09-2 kit embryos in carcass; F15– denning female with 2 kits in den tree, F31– denning female; with 3 kits in den tree)” 5. Spencer, W., et al. Southern Sierra Nevada fisher conservation assessment. 2015 "Bobcats and mountain lions have been detected with remote cameras at the bases of fisher den structures while mother and kits were known to be present (R. Sweitzer and C. Thompson, personal communications)." "At the SNAMP site, the carcass remains of 2 denning females were found within a few hundred meters of their den trees, and forensic analyses determined that both had been killed by bobcats. In 1 of those cases, images from remote cameras focused on the den tree included a bobcat with a fisher kit in its mouth, with the mother’s carcass on the ground within a few meters of the tree."

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”1 “…the ability of the species to establish a self sustaining population is affected by predation from its primary predator, the bobcat”4 1. Wengert, G. Trends in Fisher Predation in California. 2011 4. Halsey, S. Modeling predator habitat to enhance reintroduction planning. ​2015. Wengert, G. Trends in Fisher Predation in California. 2011. "Predation may be important for resident fishers (in addition to translocated fishers)" Predation, "may be very important for already small, compromised populations" "...even modest increases in mortality rates (10-20%) could prevent population expansion..." To determine whether or not predation is a limiting factor, the author suggests, "deriving some index of bobcat...population dynamics over the years, determine if bobcat populations increased during the 20th century, possibly using trapping records" and, "determine if predation rates correspond with bobcat population size.” Halsey, S. Modeling predator habitat to enhance reintroduction planning. ​2015. "The success of species reintroduction often depends on predation risk and spatial estimates of predator habitat. The fisher is a species of conservation concern and populations in the western United States have declined substantially in the last century. Reintroduction plans are underway, but the ability of the species to establish a self sustaining population is affected by predation from its primary predator, the bobcat." "Minimizing the threat of predation is especially important for species that are reintroduced after a long absence, for species that occur at low numbers, or for particularly sensitive species such as the fisher."

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)7 Kern County (located within the Southern Sierra Nevada ESU) represents 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 the Department's summary recommendation (to not list the northern ESU but to list the southern ESU) and their Status Review of the Fisher, they cite that, "Predation risk for females also varied seasonally: over 70% (19 of 25) of female predation deaths by bobcats occurred late March through July, the period when fisher kits are still dependent on their mothers for survival (Highley et al. 2013:35, Wengert et al 2014)."   Wengert, G. Trends in Fisher Predation in California. 2011. "Predation ranks as highest cause of mortality" and cause, "60% of all documented fisher mortalities" "60% killed by bobcats" which is nearly twice as much as the next predator "Most female fishers killed by bobcats" "Predation may be important for resident fishers (in addition to translocated fishers)" Predation, "may be very important for already small, compromised populations" "...even modest increases in mortality rates (10-20%) could prevent population expansion..." To determine whether or not predation is a limiting factor, the author suggests, "deriving some index of bobcat...population dynamics over the years, determine if bobcat populations increased during the 20th century, possibly using trapping records" and, "determine if predation rates correspond with bobcat population size." Wengert, G. Ecology of intraguild predation on fishers (Martes pennanti) in California. 2013. The abstract indicates, "bobcats killed only female fishers."  Sweitzer, R. and Barrett, R. SNAMP Fisher Study: Sources of Mortality. 2009 The graph, BASIC MORTALITY RESULTS: Fisher Mortalities by Season, indicates that the overwhelming majority of predation occurs during Spring when fishers are giving birth and rearing young. The graph, BASIC RESULTS: Apparent size‐related pattern of predation by different species of carnivores, note that 60% were juvenile females and 40% were adult females. "All bobcat kills have been female fishers; bobcats detected at 5 different dens." "3 bobcat-killed adult females were reproductive at death (F09-2 kit embryos in carcass; F15– denning female with 2 kits in den tree, F31– denning female; with 3 kits in den tree)" Halsey, S. Modeling predator habitat to enhance reintroduction planning. ​2015. "The success of species reintroduction often depends on predation risk and spatial estimates of predator habitat. The fisher is a species of conservation concern and populations in the western United States have declined substantially in the last century. Reintroduction plans are underway, but the ability of the species to establish a self sustaining population is affected by predation from its primary predator, the bobcat." "Minimizing the threat of predation is especially important for species that are reintroduced after a long absence, for species that occur at low numbers, or for particularly sensitive species such as the fisher." Spencer, W., et al. Southern Sierra Nevada fisher conservation assessment. 2015 "Felids are associated with >80% of all known or suspected predation deaths on SNAMP and KRFP from 2007 to March 2013 (N=50) (Wengert 2013). "Across California, predation accounts for 73% of female mortality and 45% of male mortality (Wengert et al. 2014)." "In the southern Sierra Nevada, bobcats and lions each account for 23% of all mortality, with bobcats killing female fishers and lions mostly responsible for killing males...(Wengert et al. 2014)." "Bobcats and mountain lions have been detected with remote cameras at the bases of fisher den structures while mother and kits were known to be present (R. Sweitzer and C. Thompson, personal communications)." "At the SNAMP site, the carcass remains of 2 denning females were found within a few hundred meters of their den trees, and forensic analyses determined that both had been killed by bobcats. In 1 of those cases, images from remote cameras focused on the den tree included a bobcat with a fisher kit in its mouth, with the mother’s carcass on the ground within a few meters of the tree."