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Endemic Small Mammals of Southeastern Alaska: Evolutionary Diversity, Ecology, & Conservation. Winston P. Smith USDA Forest Service, PNW Research Station Forestry Sciences Laboratory Juneau, AK 99801-8545 USA. Acknowledgments :.

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Endemic Small Mammals of Southeastern Alaska: Evolutionary Diversity, Ecology, & Conservation

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Endemic small mammals of southeastern alaska evolutionary diversity ecology conservation l.jpg

Endemic Small Mammals of Southeastern Alaska: Evolutionary Diversity, Ecology, & Conservation

Winston P. Smith

USDA Forest Service, PNW Research Station

Forestry Sciences Laboratory

Juneau, AK 99801-8545 USA

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WRANGELL, THORNE BAY and CRAIG Ranger Districts, Tongass National Forest.

UAM: Joe Cook, Steve MacDonald, Chris Conroy, John Demboski, Karen Stone, and Amy Runck.


Jeff Nichols, field crew leader and analytical support;

Scott Gende,analytical support and comments on presentation and completion reports.

Lillian Petershoare and JFSL Library.

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Background – Setting:

  • _________________________________________________________________

  • Unique attributes - dynamic recent geological history - naturally fragmented and isolated habitat - largest NF and largest remaining temperate rainforest - spatial and temporal heterogeneity

  • Limited information on natural history

  • Depauperate small mammal fauna

  • High potential for endemism

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Background – Planning:

  • _________________________________________________________________

  • Extensive clearcut logging since 1954: - 50% of most productive forest on some islands – 40+% of some watersheds - >300 yrs to develop old forest features

  • TLMP - endemic small mammals ranked as highest risk of extinction;

  • Conservation strategy - metapopulation framework- lacks empirical foundation

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Land Mammal Fauna

  • _________________________________________________________________

  • 87 islands + 24 mainland localities

  • 45 land mammal species - 65 small (<10kg) mammal taxa:15 endemic 11 confined 36 widely distributed, 3 unknown;

  • Mammal fauna – nestedstructure with varying genetic divergence: - colonization rather than extinction; - significant relationship between isolation and species richness; - competition influenced similarspecies (e.g., bears, shrews);

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Land Mammal Fauna

  • _________________________________________________________________

    - neo-endemics (flying squirrel) and paleo- endemics (marten); - number of endemics on outer islands suggests glacial refugia; - some taxa have affinities with eastern NA forms (e.g., flying squirrel, marten);

  • Most species – Upper Lynn Canal;

  • Most endemics – Mainland Subregion;

  • Ermine show highest degree of endemism with 5 subspecies representing 3 clades. (map)

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Mustela erminea

Distribution in SE Alaska

MacDonald and Cook 1996

M. e. arctica



M. e. salva



M. e. alascensis

M. e. celenda

M. e. seclusa


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Peromyscus keeni1

Distribution in SE Alaska

MacDonald and Cook 1996

*Island Endemics

P. k. algidus

*P. k. sitkensis

P. k. macrorhinus





*P. k. hylaeus


*P. k. oceanicus

1Hogan et al. 1993

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Island Biogeography

Processes: colonization & extinction Variables: island size, distance from mainland, vagility












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Community Dynamics and Structure

S = 4

S = 7




S = 9

S = 3


Species Richness(S)


S = 12

S = 14






S = 3

S = 5


Island area


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Faunal Extinctions







Glacial Advance






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Regional Colonization





Glacial Retreat








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Southern red-backed vole

Photo by P. Myers

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Natural History:Red-backed vole


  • Nearctic Distribution-in SE Alaska, southern mainland and nearshore islands;

  • Mesic forest habitat specialist;

  • Omnivorous, but primarily eats fungi (mycophagous) in the Pacific Northwest;

  • Sensitive to overstory removal and fire in western coniferous forests;

  • Influenced by landscape context, but little evidence of edge effects.


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Clethrionomys gapperi

Distribution in SE Alaska

MacDonald and Cook 1996

*Island Endemics





C. g.


*C. g. wrangeli

*C. g. solus

C. g. phaeus

C. g. saturatus

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Prince of Wales Flying Squirrel

  • Markedly different from PNW populations

  • Nocturnal, active year-


  • 1 litter (2-4 young)/year

  • Reputed old-growth

    habitat specialist

  • Mycophagist in PNW

  • Vulnerable to isolation

    in managed landscapes


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Glaucomys sabrinus

Distribution in SE Alaska

MacDonald and Cook 1996

G. s. zaphaeus

G. s. alpinus





G. s. griseifrons


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Research Objectives:


  • Estimate density of red-backed voles and flying squirrels among habitats;

  • Contrast seasonal abundance, age and sex composition, body condition, survival, and reproductive condition of voles and squirrels among habitats;

  • Examine habitat use and density relative to microsite and stand-level vegetative and structural features.

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Study Area (voles):


  • Wrangell Island

  • 4 habitats:

    - 3 unmanaged habitats in largely unmanaged landscapes;

    - thinned young growth stands within

    watershed with ~40% POG clearcut .

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Gap-Phase Old-Growth Forest

Structurally heterogeneous, vertically and horizontally - large (>150 cm), old (>800 yr) trees.

Northerly exposure

<500 m elevation

Fine scale disturbance

Sitka spruce/ western hemlock

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Multi-Cohort Old-Growth Forest

Southerly exposure;

Catastrophic disturbance per 100-200 yr;

Heterogeneous stands of even-aged patches ;

Uniform diameter, dense canopy forest: 100-102ha.

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Unmanaged Peatland-scrub/ Mixed-conifer Forest

Structurally complex, biologically diverse communities.

Spatially heterogeneous: from open muskeg to forest over a scale of 101 – 102 m.

2 replicates in 1 watershed.

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Thinned Young Growth (25 yr-old)

-pre-commercial thinning 2-3 yr prior to study initiation;

-2 replicates within the same watershed.

Dense understory of herbaceous and woody plants and slash.

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Study Design:


  • Two replicates each of 4 habitats;

  • Replicates within the same watershed but >800 m apart;

  • 1-ha grid (11 X 11) + 8 assessment lines per replicate with 2 traps per station (n = 242);

  • Live trap spring 1999-2000 and early autumn 1998-2000.

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Study Area (squirrels):


  • North-Central Prince of Wales Island

  • 2 habitats: 1) POG (mostly gap-phase) and 2) peatland-scrub/mixed-conifer;

  • 1) two ends of a continuum of forest cover;

    2) peatland-scrub/mixed-conifer - little commercial, but potential ecological value.

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Study Design:


  • Three replicates each of 2 habitats in largely unmanaged landscapes;

  • Replicates in the same watershed but >1 km apart;

  • 13-ha grid (10 X 10 array of traps);

  • Live trap spring and early autumn 1998-2000.

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RESULTS: Demography

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Mean Effective Area Sampled: Wrangell Red-backed Voles

  • First estimates for red-backed voles, which precludes comparison of density with earlier studies;

  • Effective area sample was an order of magnitude larger than grid;

  • Effective area sampled was significantly greater in gap-phase old-growth than in other habitats – relative comparisons among habitats are therefore invalid.

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Wrangell Red-backed Vole Density Spring1999 - 2000

  • Density higher in 1999 than 2000 with significant differences in multi-cohort and gap-phase old-growth;

  • Density lower in peatland/mixed-conifer in both years but significant only in 1999.

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Wrangell Red-backed Vole Density Autumn1998 - 2000

  • Density higher in 1998 than 1999 or 2000 with significant differences in all habitats;

  • Peatland/mixed-conifer consistently had lowest densities of voles with significant differences in 1999 and 2000;

  • Some evidence that thinned YG may serve as a habitat sink.

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Wrangell Red-backed Vole Population Attributes among Habitats

  • Age and sex ratios were similar among habitats;

  • Summer survival and percentage of reproductive females were significantly lower in YG than other habitats – winter survival also was lower but not statistically significant.

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Prince of Wales Flying Squirrel Seasonal Movements

  • Mean maximum distance moved was similar between habitats and seasons, averaging about 110 yards;

  • Home ranges also were similar between seasons and and habitats and ranged from about 5.5 acres to about 9.5 acres.

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POW Flying SquirrelDensity Spring1999 - 2000

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POW Flying SquirrelDensity Autumn 1998 - 2000


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POW Flying SquirrelSurvival and Productivity

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Densities in the Pacific Northwest

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  • Competitive release

  • Reduced predation pressure

  • Diet

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RESULTS: Habitat Relations

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Logistic Regression Model – Spring 1999-2000:Red-backed Voles

  • Deciduous shrub cover (+) within 1.5 meters of the forest floor was the most significant variable influencing vole microhabitat selection overall:- by a factor of 2 in multi-cohort OG and 3 in peatland/mixed-conifer.

  • Moss cover (-), density of stumps(+) and density of small snags and saplings (+) were correlates of microhabitat use in gap-phase, thinned YG, and peatland/mixed-conifer.

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Logistic Regression Model - Autumn 1999-2000:Red-backed Voles

  • Deciduous cover again had the greatest influence on microhabitat selection overall:- cover between 0.3 – 1.5 m had 2-fold (-) in gap-phase;- cover < 0.3 m had 5-fold (+) in gap- phase and 5-fold (-) in peatland/mixed- conifer.

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Discriminant Model- Spring 1999-2000:Red-backed Vole

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Discriminant Model- Autumn 1999-2000:Red-backed Vole

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Red-backed Vole Density &Decayed Downed Wood

Explained about 90% of variation in density

Vole density (ha)

Decay IV (volume/ha)

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Red-backed Vole Density & Conifer Seedling Cover

Explained about 85% of variation in vole density

Vole density (ha)

Conifer cover (%) <30 cm

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Spring 1999-2000


Decayed wood class IV (+)

Soft snags 10-49 cm dbh (-)

Coarse woody debris (+)

Decayed wood class III (+)

Conifer cover 0.3 –1.5 m (-)

Conifer cover <0.3 m (-)

Water ground cover (+)

Moss ground cover (-)

Trees 10-49 cm dbh (-)

Autumn 1999-2000


Decayed wood class IV (+)

Soft snags 10-49 cm dbh (-)

Coarse woody debris (+)

Decayed wood class III (+)

Conifer cover 0.3 –1.5 m (-)

Conifer cover <0.3 m (-)

Trees 5-10 cm dbh (-)

Habitat Correlates of Density: Red-backed Vole

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Logistic Regression Model:Northern Flying Squirrel

  • Density of trees >74 cm dbh and cover of Vaccinium most influenced microhabitat use during spring and autumn:- in peatland/mixed-conifer large tree density increased capture probability by a factor of 3 during spring and 17 in autumn;

  • Most influential habitat feature in gap-phase OG was ground cover of water was inversely correlated with microhabitat use.

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Discriminant Function Model:Northern Flying Squirrel

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Glaucomys sabrinusDensity and Live Trees >74 cm DBH

Explained about 65% of variation in squirrel density


Trees >74 cm dbh/ha

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Spring 1998-2000


Moss ground cover (+)

Decayed wood class I (+)

Decayed wood class I (+)

Decayed wood class IV (+)

Autumn 1998-2000


Trees >74 cm dbh (+)

Trees 5-10 cm dbh (-)

Trees 10-49 cm dbh (-)

Ecological Correlates of Density: Northern Flying Squirrel

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  • Current taxonomy under-represents diversity & complexity of mammal fauna;

  • High likelihood of undocumented endemic taxa, especially on mainland;

  • Outer islands show greater divergence and may contribute more genetic diversity;

  • POW flying squirrel differs markedly from northern flying squirrel in PNW;

  • Habitat loss will increase extinction risks, especially endemics of small islands.

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Population Ecology


  • Peatland-scrub/mixed conifer may support breeding populations of flying squirrels, but not red-backed voles;

  • Small HCAs likely large enough to support breeding populations of flying squirrels;

  • Voles occur in thinned YG, but it may function as a habitat sink;

  • Vole captures most often correlated with deciduous cover, but relationship and ecological impact varied among habitats -

    CANNOT ignore habitat context;

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  • Vaccinium- majorcomponent of “factors” correlated with autumn vole captures in Young Growth and Gap-Phase habitats;

  • Moss in YG during autumn may reflect vole needs for moist microsite conditions;

  • POG is primary habitat of POW flying squirrel, which may have a more general lifestyle than populations in PNW;

  • Stand level - vole density directly related to coarse woody debris and decayed downed wood, inversely related to conifer cover and dead saplings in the understory;

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  • Flying squirrel captures most influenced by large tree and snag density and Vacciniumcover in peatland/mixed-conifer where it may be limiting;

  • Stand level - squirrel density related to large tree density and decayed wood;

  • Inferences limited because of annual population variability, its influence on habitat use, and limited duration of study.

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Management Implications


  • Select-harvest of POG likely have minimal impacts to flying squirrel populations;

  • HOWEVER, select harvest of mixed-conifer forests likely will markedly reduce habitat capability for flying squirrels;

  • Viability risk for Wrangell Island vole and POW flying squirrel likely less than suggested from research on these species elsewhere.

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Information Needs


  • Systematic inventory and genetic analysis of mammals, especially on nearshore and outer small (<100,000 acre) islands;

  • Statistically robust sampling protocols to document “absence” of mammal taxa;

  • Long-term (>5 years) population data;

  • Study vole and flying squirrel populations in managed stands;

  • Dispersal success of flying squirrels in managed landscapes.

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Products from TLMP Support


  • 2000. Foraging ranges of radio-marked marbled murrelets in southeast Alaska. Condor 102: 452-456.

  • 2001. Dawn survey counts of marbled murrelets: site and annual variation, sampling effort, and statistical power. Wildlife Society Bulletin 29:568-577.

  • 1999. Relations of small mammal populations to even-aged shelterwood systems: a comment. Journal of Wildlife Management, 63(4): 1376-1380.

  • 1998. Bald eagle nesting in relation to clearcut logging in Southeast Alaska. Biological Conservation 83(2): 121-126.

  • 1998. Increasing point count duration increases standard error. Journal of Field Ornithology, 69(3): 450-456.

  • 2001. Bird, mammal, and vegetation community surveys on Research Natural Areas in the Tongass National Forest. USDA Forest Service Research Paper-PNW-RP-535. Pacific Northwest Research Station Portland, OR. 44 p.

  • 2002. Dietary uniqueness of northern flying squirrels in southeast Alaska. Canadian Field-Naturalist.

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Products from TLMP Support (continued)


  • 2000. The northern flying squirrel (Glaucomys sabrinus) as a management indicator species for the Tongass National Forest Land and Resource Management Plan: Assumptions, recent information, and priorities for studies and monitoring. Working Document, USDA Forest Service, Alaska Region, Juneau, AK.

  • 2001. Small mammals and forest interactions: mycorrhizal fungi as model organisms for understanding natural webs. Proceeding of the Non-timber Forest Products Convention, November 2001, Anchorage, AK.

  • In Press. Ecology and conservation of arboreal rodents of the Pacific Northwest. In: Mammal community dynamics in western coniferous forests: management and conservation, Zabel CJ, Anthony RG, editors. Cambridge University Press.

  • In Press. Demography of the Prince of Wales Island flying squirrel: an endemic of southeastern Alaska temperate rainforest. Journal of Mammalogy.

  • In Review. Maintaining wildlife habitat in southeastern Alaska: implications of new knowledge for forest management and research. (to Landscape and Urban Planning).

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Products from TLMP Support (continued)


  • In Review. Demography of two endemic forest-floor mammals in southeastern Alaska temperate rainforest. Journal of Mammalogy.

  • In Review. Sustainable management of wildlife habitat and risk of extinction Conservation Biology.

  • In Review. Cost of transport in the northern flying squirrel, Glaucomys sabrinus. Journal of Mammalogy.

  • In Review. Evolutionary diversity and ecology of endemic small mammals of southeastern Alaska with implications for forest management. (to Wildlife Monographs)

  • In Review. Habitat correlates of flying squirrel abundance in temperate rainforests: implications for ecosystem management. (to Ecological Applications)

  • In preparation. Habitat correlates of abundance of two endemic forest floor mammals of southeastern Alaska temperate rainforests.

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