The objectives of this study were to document the presence of breeding populations of wood frogs (Rana sylvatica) in Denali National Park and Preserve and to examine landscape and habitat factors associated with population distribution. Surveys were conducted within 41 circular plots, each 1 km in diameter. All lentic sites were surveyed within each 1-km plot to determine the presence of wood frogs and to collect habitat data. Of the 219 sites surveyed, breeding activity (the presence of eggs or larvae) was observed at 98 sites (45%). Larger and less isolated sites had a higher incidence of observed breeding activity. Also, breeding activity was more frequently observed at sites with more emergent vegetation and more woody vegetation in the riparian zone, especially riparian zones with alder and spruce. Breeding activity was less often observed at deeper sites, sites with a permanent stream connection, sites where sphagnum (peat) dominated the substrate, and sites with beaver activity. A multifactor habitat model was developed using classification trees and parsimonious model selection protocol. The final model identified proportion of woody vegetation in the riparian zone, dominant substrate type, presence of alder in the riparian zone, and observed beaver activity as 4 habitat factors that accurately described breeding activity patterns in the study area. The results show that breeding populations of wood frogs saturate the landscape in the Wonder Lake region with nearly half of the lentic habitat sites being used by wood frogs. The majority of the sites were well into the shrubby tundra and >1000 m from boreal forest, suggesting that wood frogs in Alaska may frequent non-canopied areas at higher elevations as long as shrubby vegetation is present in riparian areas.
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1 September 2006
DISTRIBUTION PATTERNS OF WOOD FROGS (RANA SYLVATICA) IN DENALI NATIONAL PARK
D Grant Hokit,
Andrew Brown
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Alaska
boreal forest
breeding activity
canopy cover
Denali National Park
distribution patterns
habitat associations