Presentation on theme: "Endemic Small Mammals of Southeastern Alaska: Evolutionary Diversity, Ecology, & Conservation Winston P. Smith USDA Forest Service, PNW Research Station."— Presentation transcript:
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: ____________________________________________________________________ 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.
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
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
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 – nested structure with varying genetic divergence: - colonization rather than extinction; - significant relationship between isolation and species richness; - competition influenced similarspecies (e.g., bears, shrews);
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)(map)
Mustela erminea Distribution in SE Alaska MacDonald and Cook 1996 M. e. alascensis Juneau * N CANADA. M. e. celenda M. e. seclusa M. e. salva M. e. arctica
Peromyscus keeni 1 Distribution in SE Alaska MacDonald and Cook 1996 P. k. macrorhinus * P. k. sitkensis * P. k. oceanicus Juneau * N CANADA. P. k. algidus * P. k. hylaeus 1 Hogan et al. 1993 * Island Endemics
Island Biogeography Continent Processes: colonization & extinction Variables: island size, distance from mainland, vagility island immigration
Community Dynamics and Structure Continent island Island area Colonization Extinction Species Richness (S) equilibrium S = 4 S = 9 S = 14 S = 7 S = 3 S = 5 S = 12 S = 3
Faunal Extinctions Continent island Glacial Advance Refugia N
Regional Colonization Continent island Glacial Retreat Refugia N
Southern red-backed vole by P. Myers Photo by P. Myers
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)
Clethrionomys gapperi Distribution in SE Alaska MacDonald and Cook 1996 C. g. stikinensis * C. g. wrangeli * C. g. solus C. g. phaeus C. g. saturatus Juneau * N CANADA * Island Endemics
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 ) ( map )
Glaucomys sabrinus Distribution in SE Alaska MacDonald and Cook 1996 G. s. zaphaeus Juneau * N CANADA. G. s. griseifrons G. s. alpinus
Research Objectives: ___________________________________ 1.Estimate density of red-backed voles and flying squirrels among habitats; 2.Contrast seasonal abundance, age and sex composition, body condition, survival, and reproductive condition of voles and squirrels among habitats; 3.Examine habitat use and density relative to microsite and stand-level vegetative and structural features.
Study Area (voles): ________________________________________________ Wrangell Island 4 habitats: - 3 unmanaged habitats in largely unmanaged landscapes; - thinned young growth stands within watershed with ~40% POG clearcut.
Gap-Phase Old-Growth Forest Structurally heterogeneous, vertically and horizontally - large (>150 cm), old (>800 yr) trees. Fine scale disturbance Northerly exposure <500 m elevation Sitka spruce/ western hemlock
Multi-Cohort Old-Growth Forest Southerly exposure; Catastrophic disturbance per 100-200 yr; Heterogeneous stands of even-aged patches ; Uniform diameter, dense canopy forest: 10 0 -10 2 ha.
Unmanaged Peatland-scrub/ Mixed-conifer Forest Spatially heterogeneous: from open muskeg to forest over a scale of 10 1 – 10 2 m. Structurally complex, biologically diverse communities. 2 replicates in 1 watershed.
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: ______________________________________ 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): _________________________________________________ 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 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 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 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 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 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 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.
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 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.
Discriminant Model- Spring 1999-2000: Red-backed Vole Model Multivariate Factor Gap-PhaseN/A Multi-cohortN/A Thinned YGN/A Peatland-MCMoss, sapling, & deciduous shrub
Red-backed Vole Density & Decayed Downed Wood Decay IV (volume/ha) Vole density (ha) Explained about 90% of variation in density
Red-backed Vole Density & Conifer Seedling Cover Conifer cover (%) <30 cm Vole density (ha) Explained about 85% of variation in vole density
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 (-)
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.
Discriminant Function Model: Northern Flying Squirrel Model Multivariate Factor Spring Peatland-MCUnderstory cover/structure Large tree/ snag density Upland-OGN/A Autumn Peatland-MCLarge tree/ snag density Upland-OGVaccinium
Glaucomys sabrinus Density and Live Trees >74 cm DBH Trees >74 cm dbh/ha Squirrels/ha Explained about 65% of variation in squirrel density
Ecological Correlates of Density: Northern Flying Squirrel Spring 1998-2000 _____________________________________________ Moss ground cover (+) 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 (-)
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 ____________________________________ 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 Ecology ____________________________________ Vaccinium - major component 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 Ecology ____________________________________ Flying squirrel captures most influenced by large tree and snag density and Vaccinium cover 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 ____________________________________ 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 ____________________________________ 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 _____________________________________________________________ 1. 2000. Foraging ranges of radio-marked marbled murrelets in southeast Alaska. Condor 102: 452-456. 2. 2001. Dawn survey counts of marbled murrelets: site and annual variation, sampling effort, and statistical power. Wildlife Society Bulletin 29:568-577. 3. 1999. Relations of small mammal populations to even-aged shelterwood systems: a comment. Journal of Wildlife Management, 63(4): 1376-1380. 4. 1998. Bald eagle nesting in relation to clearcut logging in Southeast Alaska. Biological Conservation 83(2): 121-126. 5. 1998. Increasing point count duration increases standard error. Journal of Field Ornithology, 69(3): 450-456. 6. 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. 7. 2002. Dietary uniqueness of northern flying squirrels in southeast Alaska. Canadian Field-Naturalist.
Products from TLMP Support (continued) ___________________________________________ 8. 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. 9. 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. 10. 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. 11. In Press. Demography of the Prince of Wales Island flying squirrel: an endemic of southeastern Alaska temperate rainforest. Journal of Mammalogy. 12. 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 (continued) ___________________________________________ 13. In Review. Demography of two endemic forest-floor mammals in southeastern Alaska temperate rainforest. Journal of Mammalogy. 14. In Review. Sustainable management of wildlife habitat and risk of extinction Conservation Biology. 15. In Review. Cost of transport in the northern flying squirrel, Glaucomys sabrinus. Journal of Mammalogy. 16. In Review. Evolutionary diversity and ecology of endemic small mammals of southeastern Alaska with implications for forest management. (to Wildlife Monographs) 17. In Review. Habitat correlates of flying squirrel abundance in temperate rainforests: implications for ecosystem management. (to Ecological Applications) 18. In preparation. Habitat correlates of abundance of two endemic forest floor mammals of southeastern Alaska temperate rainforests.