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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

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

slide2
Acknowledgments:

____________________________________________________________________

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

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

SPECIAL THANKS:

Jeff Nichols, field crew leader and analytical support;

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

Lillian Petershoare and JFSL Library.

slide3
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
slide4
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
slide5
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 similar species (e.g., bears, shrews);
slide6
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)
slide7
Mustela erminea

Distribution in SE Alaska

MacDonald and Cook 1996

M. e. arctica

Juneau

*

M. e. salva

CANADA

N

M. e. alascensis

M. e. celenda

M. e. seclusa

.

slide8
Peromyscus keeni1

Distribution in SE Alaska

MacDonald and Cook 1996

*Island Endemics

P. k. algidus

*P. k. sitkensis

P. k. macrorhinus

*

Juneau

CANADA

N

*P. k. hylaeus

.

*P. k. oceanicus

1Hogan et al. 1993

slide9
Island Biogeography

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

island

island

immigration

island

island

Continent

immigration

island

island

island

island

slide10
Community Dynamics and Structure

S = 4

S = 7

island

island

Continent

S = 9

S = 3

island

Species Richness(S)

island

S = 12

S = 14

equilibrium

Colonization

island

island

Extinction

S = 3

S = 5

island

Island area

island

slide11
Faunal Extinctions

island

island

N

Refugia

island

island

Glacial Advance

Continent

island

island

island

island

slide12
Regional Colonization

island

island

N

Refugia

Glacial Retreat

island

island

Continent

island

island

island

island

southern red backed vole
Southern red-backed vole

Photo by P. Myers

natural history red backed vole
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.

(map)

slide15
Clethrionomys gapperi

Distribution in SE Alaska

MacDonald and Cook 1996

*Island Endemics

Juneau

*

CANADA

N

C. g.

stikinensis

*C. g. wrangeli

*C. g. solus

C. g. phaeus

C. g. saturatus

slide16
Prince of Wales Flying Squirrel
  • Markedly different from PNW populations
  • Nocturnal, active year-

round

  • 1 litter (2-4 young)/year
  • Reputed old-growth

habitat specialist

  • Mycophagist in PNW
  • Vulnerable to isolation

in managed landscapes

(map)

slide17
Glaucomys sabrinus

Distribution in SE Alaska

MacDonald and Cook 1996

G. s. zaphaeus

G. s. alpinus

Juneau

*

CANADA

N

G. s. griseifrons

.

research objectives
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.
study area voles
Study Area (voles):

________________________________________________

  • Wrangell Island
  • 4 habitats:

- 3 unmanaged habitats in largely unmanaged landscapes;

- thinned young growth stands within

watershed with ~40% POG clearcut .

slide20
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

slide21
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.

slide22
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.

slide23
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.

study design
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.
study area squirrels
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.

study design26
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.
mean effective area sampled wrangell red backed voles
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.
wrangell red backed vole density spring 1999 2000
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.
wrangell red backed vole density autumn 1998 2000
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.
wrangell red backed vole population attributes among habitats
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.
prince of wales flying squirrel seasonal movements
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.
slide37
Why?

Hypotheses

  • Competitive release
  • Reduced predation pressure
  • Diet
logistic regression model spring 1999 2000 red backed voles
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.
logistic regression model autumn 1999 2000 red backed voles
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.
red backed vole density decayed downed wood
Red-backed Vole Density &Decayed Downed Wood

Explained about 90% of variation in density

Vole density (ha)

Decay IV (volume/ha)

red backed vole density conifer seedling cover
Red-backed Vole Density & Conifer Seedling Cover

Explained about 85% of variation in vole density

Vole density (ha)

Conifer cover (%) <30 cm

habitat correlates of density red backed vole
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
logistic regression model northern flying squirrel
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.
glaucomys sabrinus density and live trees 74 cm dbh
Glaucomys sabrinusDensity and Live Trees >74 cm DBH

Explained about 65% of variation in squirrel density

Squirrels/ha

Trees >74 cm dbh/ha

ecological correlates of density northern flying squirrel
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
endemism
Endemism

____________________________________

  • 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.
population ecology
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;

population ecology53
PopulationEcology

____________________________________

  • 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;
population ecology54
PopulationEcology

____________________________________

  • 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.
management implications
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.
information needs
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.
products from tlmp support
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.
products from tlmp support continued
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).
products from tlmp support continued59
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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