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Porcupines An Increasingly Rare Sight in California
Mid‐elevation Mixed Conifer Forests:
Consequences for Conservation of Pacific fishers
Rick A. Sweitzer, Department of Environmental
Science, Policy, and Management, Center for
Forestry, University of California, Berkeley,
California 94720; [email protected]
“Where have the porcupines gone”
Has
their range in CA declined, if so, why?
Credit: Krissi
Russell
“The porcupine is one of the most
interesting of our wildlife fauna, and as such
deserves to be perpetuated. Mountains and
extensive forested areas will always afford
adequate habitat.”
D. Spencer 1950.
“While interesting to the nature lover
and sentimentalist, it is entirely devoid of
any positive economic value—no usable
pelt, no tasty flesh, nothing.”
Cook and
Hamilton 1957
CWHR Distribution for Porcupines in California
Habitats and Distribution in CAWide diversity of habitats Not found in hot deserts or central and
south Coastal habitatsConsidered most common in montane
conifer, Douglas fir, alpine dwarf‐shrubUncommon in hardwood, hardwood‐
conifer forests, valley‐foothill riparian,
Pinyon‐juniper woodland, low sagebrush Commonly den in congregations in rock
outcroppings (winter seasons)Sources: Taylor 1935, Woods 1973, Dodge 1982
Many have noted that porcupines are now rare or absent
from areas where they were once considered abundant,
particularly in the Sierra Nevada…
Porcupines in California: Rumors and Comments
Agencies dispersed toxicants by fixed‐wing aircraft after World War II
There was a concerted effort to poison and shoot porcupines by
several state and federal agencies during 1930s to 1970s
Agencies sent crews out with .22 rifles during winter to shoot
porcupines as recently as 1970s
Porcupines have disappeared from many areas where they were once
common, especially in the Sierra Nevada
Sources of Mortality and Natural History of Porcupines
Predation, mostly mammalian
Fisher, Mtn
lions, bobcats/coyotes, owls (kits)
Fisher and Mtn
lions can control/limit porcupines
Coyotes and bobcats less effective
Roadkill
–
focused during summer & fall
Falls/Injuries from tree climbing (minor)
Disease (minor) LIFE HISTORY:
Long‐lived with high
annual survival
Very low reproductive
rates for a rodent: 1
kit/year
Limited potential to
rebound from
predation/persecution Fishers are main predator of
porcupines where they co‐occur
Foraging Behavior and Damage to Timber/Trees by Porcupines
Winter foraging on inner bark of trees/shrubs is the
main concern; may congregate in stands of trees
Discrimination by nutrient levels can result in
significant girdling of some trees and tree death
Foraging damages leader of a tree; produces bushy
“spike top”, reduces radial growth
In plantations winter feeding has caused significant
damage/mortality to expanses of pole‐timber
Direct conflicts with
humans: chew on
tools, wires, etc. with
salt or mineral
residues (“salt drive”
assoc. with quills)
Control Methods for Porcupines
Poisons –
Strychnine‐laced salt/baits
nailed to trees, placed inside rock dens
.22 caliber rifles; systematic hunting on transects
Can be very effective during winter aided by sign
Trapping w/conibear
kill traps; inefficient
USDA actively promoted control of porcupines in U.S.
national forests starting in early 1900s
Multiple studies/pamphlets evaluating or describing most
effective poisons and methods of control
“the porcupine can be decimated
with (poison) impregnated salt
blocks.”
Cook and Hamilton 1957
Review of Historical Information on Porcupine Control in CA
Location(s) Methods Notes on abundance Source
Northeastern CA
National Forests
• Strychnine treated
salt blocks
• Organized hunts;
.22 rifles/pistols
Not discussed Keyes 1934
Modoc Nat
Forest
Strychnine salt blocks Common: captured 40
with little problem
Anthony et al.
1986
Modoc Nat
Forest, Adjacent
BLM lands
Radiotelemetry
to
facilitate more
effective baiting
Abundant: 58 captured in
2 yrs in 4 mile2
area Hoffer
1967;
Hoffer
(1967) referenced “Forest Service kill records”
–
have not found/accessed these yet
Porcupines in California: Rumors and Comments
Agencies dispersed toxicants by fixed‐wing aircraft after WW
II: No good evidence for this
Agencies poisoned porcupines and sent crews out with .22
rifles to shoot them as recently as 1970s: common recommended method, very likely true
Searching for more agency records, but there have been very
few studies of porcupine biology within California
Porcupines may have disappeared from many areas where
they were once common…
Invasion of NW California (Humboldt & Del Norte Counties) by Porcupines: Yocom
1971
Data:Not observed before 1900, scant records
before 1930 (n = 2), numerous records after 1950s
Many records in 1960s
Hypothesis:
cutting of virgin forests (Douglas fir, redwoods) created suitable
habitat conditions for porcupines– moved to Del Norte from Siskiyou in 1920s– Moved into Humboldt from Trinity, Mendocino
Porcupine expansion in NW California (Yocom
1971)
Lumber Production in Board Feet (Yocom
1971)
Surveys & Evidence of Porcupine Presence: they aren’t hard to Identify!!
Evidence of winter feeding beneath station trees
Feces in tree and rock dens
Road‐kill carcasses (common during summer/fall)
Tracks in snow; unmistakable
D. Munz, Sept 28, 2012
CSERC Camera survey image: J. Buckley
Ongoing Porcupine Survey in Sierra Nevada: CSERC –
L. Meyers, J. Buckley
INFORMATION BEING REQUESTED/COLLECTED:A)Times
and dates of sightingsB)Specific
location(s) as detailed as possibleC)Description
of porcupine behavior (if alive)D)Road
‐kills ‐
describe road condition, speed limit, etc.E)Any
other relevant information and photos
Contact: Lindsey Myers: [email protected], or call: (209) 586‐7440.
CSERC Porcupine Survey: Lindsey Meyers 2012
Table1.Summarydataonporcupine
sightings(n=24)reportedinSierra
Nevadaforests&YosemiteNational
Parkduring2010tomid2012.
Area Total Road‐killsLassen NF 1 1Plumas NF 1Tahoe NF 8 6
Stanislaus NF 8 2Yosemite NP 3
Inyo NF 2Sierra NF 1
COMMENTS:Porcupines appear uncommon to very rare in
Sierra Nevada from Yosemite NP southMostly absent from mid‐elevation forests…More common high elevation, alpine zoneNatural Resource Inventory System: only 3
porcupine reports (all Stanislaus NF) since 1980s
Photo: CSERC Photo: CSERC
Implications for Conservation of Rare Pacific Fisher in California
Historic and Current Distribution
Trapping+extensive
timber harvest after early 1900s
reduced range by 40‐50%
Fisher now absent from Sierras north of Yosemite
NP; southern Sierra population genetically isolated,
Candidate Species ESA
Photo credit: R. Powell
Resource‐Based Limiting Factors: Conditions have changed – are fishers now prey limited by reduced to absent porcupines?
Current diets of fishers in CA are unusually diverse, including squirrels, birds, reptiles, fungi, insects, and plants/berries
Are diets diverse due to recent scarcity/absence of larger mammalian prey? Porcupine detected by camera at
crest of Sierra Nevada:
Image courtesy J. Buckley, CSERC
Porcupines do appear rare or absent in southern Sierras
No porcupines detected by any UC Berkely Fisher Project cameras in Sierra NF
1 porcupine every 10 to 35 days
1 snowshoe hare 2.5 to 8 days
1 to 2 squirrels every day Source: R. Powell (1981)
“The porcupine is one of the most interesting of our wildlife fauna, and as
such deserves to be perpetuated.”
D. Spencer 1950.
THANK YOU !!
Images/Data: CSERC, Sierra
NF, so far…