SURVEY of FLYING SQUIRRELS and THEIR ASSOCIATION with VEGETATION COMMUNITIES on MOUNT DESERT ISLAND (Acadia National Park), MAINE
SURVEY OF FLYING SQUIRRELS AND THEIR ASSOCIATION WITH VEGETATION COMMUNITIES ON MOUNT DESERT ISLAND (Acadia National Park), MAINE
Final Report
By
Jennifer Higgins! Department of Wildlife Ecology, University of Maine Orono, ME 04469 & Allan F. O'Connell, Jr.2 Cooperative Park Studies Unit, National Park Service University of Maine Orono, ME 04469 & Frederick A. Servello Department of Wildlife Ecology University of Maine Orono, ME 04469
August 1998
!: Maine Department of Inland Fisheries and Wildlife, Wildlife Resources Assessment Section, 650 State St., Bangor, ME 044001-4450 2: Cooperative Park Studies Unit, Patuxent Wildlife Research Center, U.S. Geological Survey, University of Maine, Orono, ME 04469-5768 -,, ANPFSQRii
Abstract
Northern, Glaucomys sabrinus, and southern, G. volans, flying squirrels both occur in Maine, but there is uncertainty about range overlap throughout southcentral Maine where the southern flying squirrel reaches geographic range limits. Species occurrence and study of interactions in these areas provide important information on the ability of popUlations to survive 'under less than optimal conditions. We surveyed flying squirrels in Acadia National Park on Mount Desert Island (MDI), Maine during the summer of 1992. We compared vegetation characteristics between forest stands with and without squirrel populations and between capture locations and locations without captures. Northern flying squirrel populations (22 individuals) were located in two conifer stands and one mixed conifer-hardwood (i.e., deciduous) stand; a single individual also was captured in a hardwood stand. Capture rates for northern flying squirrels were within the range reported for other areas. In the mixed conifer-hardwood stand, flying squirrels were captured at locations with significantly larger deciduous trees. Deciduous seedling density was greater at capture locations than locations without captures in both conifer stands with squirrel populations (p = 0.01,0.05). Relatively dense deciduous seedlings in an aging conifer forest, typical ofMDI, may provide better cover and protection from predators. Large deciduous trees, typically with more cavities, may provide a greater opportunity for den sites. During this century there has been only one report of a single southern flying squirrel captured at a specific site (Pickett Mountain) on MDI; other reports have not been documented. We were not able to capture southern flying squirrels on MDI during this study. The occurrence of northern flying squirrels in our mixed-wood stand is evidence that southern flying squirrels did not occur in this stand because southern flying squirrels are known to displace northerns in sympatric populations. Periodic surveys should continue at about 10 year intervals to maintain the continuity of previous work on MDI. Future surveys should sample a variety of areas over the entire island, employ longer trapping periods (214 days) to insure extensive coverage for a rare species, and consider collection of voucher specimens to verify species identification, validate subsequent work, and effectively document local biodiversity. ANPFSQRiii
Table of Contents
Abstract...... 11
List of Tables...... IV
Introduction and Background...... 1
Study Area...... 2
Methods...... 2
Results and Discussion...... 3
Recommendations...... 5
Acknowledgments...... 6
Literature Cited...... 6
Appendix A...... 18 ANPFSQRiv
List of Tables
Table 1. Mean density (per ha) of trees (> I 0 cm dbh) in 8 potential habitats for flying squirrels in Acadia National Park on MD!, ME. Bold, italic type denotes areas where squirrel populations (;:::: 2 individuals) were found...... 10
Table 2. Capture rates (captures/l 00 trap nights) for flying squirrels at 8 sites in Acadia National Park on MDI, ME...... 11
Table 3. Age, sexes, and weights (g) for northern flying squirrels captured in Acadia National Park on MDI, ME...... 12
Table 4. Comparison of habitat characteristics of sites with and without northern flying squirrel populations in Acadia National Park on MDI, ME...... 13
Table 5.· The mean number oflogs/ha and snags/ha for three sites where flying squirrels occurred (> 1 individual) and 4 sites where no squirrels were captured in Acadia National Park on MDI, ME...... 14
Table 6. Density (trees/ha) and Shannon index of species diversity for tree species> 4 dbh at eight sights in Acadia National Park on MD!, ME...... 15
Table 7. Comparison of tree diameters and stem densities between trap sites where squirrels were captured compared to locations without squirrel captures in Acadia National Park on MDI, ME...... 17 ANPFSQRl
Introduction and Background·
Two species of flying squirrels occur in North America and both occur in Maine. Northern flying squirrels are widespread throughout the state (Hall 1981: 450) whereas the range and distribution of southern flying squirrels are less well known (Cameron 1976). Hall's (1981) geographic range limit for the southern species includes a portion of Maine (modified from the first edition of Hall and Kelson [1959]) but no records ofvolans are listed for this state. The scientific literature, however, documents six occurrences ofthe southern flying squirrel in Maine (Cameron 1976) with the most northern sites at North Anson and Eastport. Muul (1968) indicated the range limit for volans was limited by temperature, and Cameron (1976) points out that North Anson is at the "extreme limits" of these temperature isotherms. MDI, located along the mid-coast of Maine and south of North Anson, is within the range limits for the southern flying squirrel, and although both species have been reported from MDI, the status ofvolans remains uncertain because reports have been poorly documented. The two species can be sympatric, although the relationship has been termed variable and exclusive, even unstable (Weigl 1978, u.s. FWS 1990). Thus, areas like MDI, where the southern flying squirrel reaches range limits and potentially overlaps with the northern species, may provide an opportunity to study unique interspecific and sympatric relationships (Weigl 1978, Payne et al. 1989). Furthermore, Acadia National Park is the dominant land use on MDI, and because the National Park Service (NPS) seeks to inventory local resources, detailed information on flying squirrels will assist Park managers in making more informed decisions related to resource management. American flying squirrels are associated with different forest communities. Northern flying squirrels are typically found in conifer vegetation that include mature red spruce, Picea rubra, balsam fir, Abies balsamea and yellow birch, Betula alleghaniensis, but can also be found in deciduous vegetation (i.e., hardwoods), especially when overlap with the southern flying squirrel does not occur. Southern flying squirrels are usually associated with the deciduous forest (MuuI1968, Weigl 1978) and are considered vegetation specialists compared to their northern congeners. Preferred vegetation communities consist of mature hardwood stands composed of red oak, Quercus rubra, sugar maple, Acer saccharum, American beech, Fagus grandifolia, and yellow birch. Other tree species often found on these sites are white birch, Betula papyrifera, white ash, Fraxinus americana, butternut, Juglans cinerea, trembling aspen, . Populus tremuloides, and eastern hemlock, Tsuga canadensis (Cameron 1976). A high density of snags, downed logs, and dense canopy cover are important for both species of American flying squirrels (Carey et al. 1997), and although omnivorous, each generally prefers different foods (Weigl 1978). Determination of important habitat characteristics for flying squirrels in the northeastern United States has been limited to a few studies, with most work done on the southern species (Madden 1974, Fridell and Litvaitis 1991). The objectives ofthis study were to review the historical information on flying squirrels on MDI and conduct a survey to document the occurrence and distribution of northern and southern flying squirrels in Acadia National Park. We also evaluated several habitat characteristics reported to be important for these rodents in other parts of their ranges. ANPFSQR2 . ) Study Area
This study was conducted on MDI, located along the mid-coast Maine (44° 12' - 44° 27" 2 N, 68° 10' - 68° 27' W). MDI's land area is 281 km , about half of which is within Acadia National Park. MDI's physiographic location is along the vegetative transition zone between the central hardwood and spruce-fir-northern hardwood forest communities (McMahon 1990). Much of the current vegetation on the island is spruce fir within a matrix of northern hardwoods (Westveld et al. 19S6). Nearly 113 of the MDI's acreage was burned in 1947; this event has altered vegetative succession in the burned area, encouraging the growth of deciduous tree species like aspen and birch. We selected vegetation communities for study sites that were representative ofMDI's flora and where flying squirrel species were likely to occur: conifer, hardwood, and mixed-wood. Dominant tree species on conifer sites were red spruce, white pine, Pinus strobus, and northern white cedar, Thuja occidentalis. Red oak, white pine, northern white cedar, red maple, and trembling aspen were common in the mixed hardwood-conifer sites and hardwood sites were represented by red oak and maple, American beech, sugar maple, and bigtooth aspen, P. grandidentata.
Methods Based on known, preferred habitat characteristics for northern and southern flying squirrels (MuuI1968, Weigl 1978, U.S. FWS 1990), we reviewed vegetation cover maps ofMDI (1979) and selected 8 sites (i.e., forest stands) potentially suitable for flying squirrels: conifer, mixed conifer-hardwood, and hardwood (Table 1). We set traps along 1200 total meters of parallel transects at SO m intervals with SO m between each transect line to maximize coverage through a particular vegetation type (see Appendix A for specific location and orientation of transects). Two traps were placed 1.S m above the ground in tree boles of mature trees, and one trap was placed on the ground at each SO m interval along a transect. We divided trapping into 4 separate sessions beginning in June and trapped two sites simultaneously until completion in August. We used Havahart® traps (SO cm x SO cm x 180 cm) with a mixture of peanut butter and oats for bait. Traps were baited and opened at sunset, checked at sunrise, and then closed to avoid non-target captures. Upon capture, squirrels were placed into mesh bags to be weighed and confirm species identification. We identified flying squirrels species by examining the color of the base of ventral hairs (U.S. FWS 1990). We also aged each individual « SS g = juvenile, grey dorsally = juvenile; red, brown = adult), measured hind foot and body length, and recorded sex and reproductive status (i.e., nipple size and testes descent). We clipped hair on the tail to uniquely identify individuals for recapture (Wells-Gosling 1985:98). At each trap site, we measured the following habitat characteristics: tree diameter at breast height (dbh) (> 10.2 cm using a prism), a 20 m (radius) circular plot for small trees (> 2.S4 cm dbh and < 10.16 cm dbh) and logs and snags, a 10 m circular plot for saplings (> 1.37 m high and < 2.54 cm dbh), and a 4 m circular plot for seedlings « 1.37 m high). We determined dbh and basal area by species, and stand classification as either hardwood or conifer (> 7S%) or mixed (> SO% or < 7S%). Counts of seedlings, saplings, and small trees were recorded in the 4 m, 10 m, and 20 m plots, respectively. Snags and logs were recorded at each transect point ANPFSQR3 · ~) using the classification recommended by Thomas et al. (1979). We calculated the diversity of tree species at each site using the Shannon species diversity index (Pielou 1966). Statistical analyses of habitat characteristics were conducted at two levels, at the forest stand level (i.e., combination of all trap sites on transects in a single forest stand) and microhabitat level (i.e., individual trap locations along transects). We compared differences in vegetation between sites with and without squirrel populations using t-tests. We used a Kruskal Wallis test to compare differences in snag and log density, tree, small tree, sapling, and seedling densities between locations with flying squirrels captures and locations without captures. To accommodate small sample sizes and balance the probability between Type I and Type II errors
(Tacha et al. 1982), we chose to set 0< = 0.10 to denote significance.
Results and Discussion
We captured only northern flying squirrels during this study. Squirrels were captured in two conifer stands and one mixed-wood stand and one individual was captured in a hardwood stand (Aunt Betty's Pond) (Table 2). Capture rates (x = 3.19 squirrels/100 trap nights, range 1.74 - 4.20, Table 3) were greater than other reports for this species in North Carolina (1.21100 trap nights) or West Virginia (0.8/100 trap nights). In the southern Appalachians, Weigl (1990) reported variable capture rates. Observations by park personnel during this study reported flying squirrels at some study sites where we did not capture any individuals, suggesting that greater dispersion of traps and longer trapping periods may be necessary to insure complete coverage of MDI. We used color dye to mark individuals but the dye proved ineffective as a long-lasting mark; clipping of tail hair proved to be successful and we used this technique to validate recaptures. Measuring active individuals through mesh bags or traps was not successful, and accurate data were collected only on sex, weights and age (Table 2). For future work, if accurate measurements are needed, squirrels should be immobilized for proper handling. Differences were not detected in mean dbh or density of deciduous and conifer trees, mean log or snag density, between stands with and without squirrel populations (Tables 4 and 5). Although woody plant diversity was generally greater in conifer and the mixed-wood stands with squirrels compared to conifer and mixed-wood stands without squirrels (Table 6), differences were small. Tree density varied between stands probably resulting in low power to detect significant differences (Table 3). At the microhabitat level, we detected some differences in vegetation parameters that may be important for flying squirrels on MDI. In the mixed-wood stand (Compass Harbor), deciduous tree dbh was larger where squirrels were captured compared to locations without captures (Table 7). Conversely, on one conifer stand (Beech Mt.), squirrels were captured where deciduous tree diameter was significantly smaller. Interestingly, mean dbh of deciduous trees in the mixed-wood stand was nearly twice the size of deciduous trees at capture locations on the two conifer stands. Flying squirrels have been found to prefer deciduous trees with snags (Carey et al. 1997) that are usually associated with larger (and older) trees used for denning. Older deciduous trees also have rougher bark that provides squirrels greater maneuverability (Sonenshine and Levy 1981, Bendel and Gates 1987). Based on these results, squirrels may prefer deciduous trees once they reach a certain size and exhibit certain physical qualities, thus the association with larger trees in the mixed-wood stand. In several past studies of flying squirrels, understory vegetation has not been considered an important indicator of ANPFSQR4
habitat suitability (Sonenshine and Levy 1981, Payne et al. 1989, but see Bendell and Gates 1987). On MDIunderstory vegetation also varied, but with a few exceptions. At capture locations in one conifer stand (Beech Mountain), density of small trees was significantly less for both conifer and deciduous species compared to locations without captures (Table 6). We also detected differences in conifer sapling density between capture locations and locations without captures in both conifer stands, but trends were not evident (Table 6). Deciduous seedling density was greater at capture locations in each of the two conifer stands with squirrel populations (Table 6). Dense seedlings with leaves may offer increased cover and protection for female squirrels (and young) when away from their dens, especially near the ground. This may be important in an aging conifer forest typical ofMDI where breaks in the canopy and sparse undergrowth allow better visibility for predators. Flying squirrels are thought to be particularly vulnerable to predators when not gliding, and whether on the ground or in trees, protection is best afforded in dense understory vegetation. Finally, cedar has been found to be important in some areas for nest construction (Sonenshine and Levy 1981), and northern white cedar was common in all stands where we captured squirrels. Interactions between northern and southern flying squirrels indicate that the southern species is more aggressive and where both occur may displace the northern species into conifer vegetation (Weigl 1978). In addition, the southern flying squirrel carries a parasitic nematode that may be deadly to the northern species (Weigl 1977). The occurrence of northern flying squirrels in conifer and mixed conifer-hardwood vegetation on MDI suggests that the more aggressive southern flying squirrel did not occur on MDI in our study sites, particularly the mixed wood stand. Our results are further supported by Garman's (1991) recent survey on MDI that found northern flying squirrels in conifer as well as mixed wood vegetation. A biological survey of Pickett Mountain generated the first report of the southern flying squirrel (G. [Sciropterus] volans) (Twitchell and Crockett 1925) from MDI. The authors report capturing one specimen using a butterfly net in a "mixed conifer" stand with over 50% spruce-fir vegetation. It is many years later before Coman (1981, 1987) and Grierson (1995) publish reports that list the southern flying squirrel as occurring on MDI. Grierson (1995) listed volans as the only flying squirrel species as occurring on MDI but she thought that the listing was a publishing error (R. Grierson pers. commun., July 1998). Grierson (1995) provided measurements and a photograph for this flying squirrel account, but measurements were identical to those listed for the northern flying squirrel in Godin (1977: 102), a reference used by Grierson (1995). The photograph provided no information as to location source, and it is difficult to differentiate between these species with one photo that shows only dorsal hair. Coman includes volans in the last 2 editions (1981, 1987) of his publication on MDI fauna, but makes only general reference to location (i.e.. , deciduous forest) and reports no voucher specimens, despite noting receipt of dead individuals. Nevertheless, we recognize that other possibilities may be valid about the occurrence of southern flying squirrels on MDI. This species may have occurred on MDI earlier this century, but is not now endemic to the island. Confirmation to species for American flying squirrels can be difficult, making errors possible. Finally, our survey (and previous ones) may not have been extensive enough to capture southern flying squirrels. G. sabrinus has been documented on MDI several times during this century (Stupka 1932, Stupka 1933, Stupka 1935, Branin 1939, Manville 1942, Calhoun 1950, Calhoun 1951, Davis 1961, Allen 1969, Garman 1991). Branin (1939) and Manville (1942) referenced voucher specimens in scientific collections at Acadia National Park in Bar Harbor, ME. We examined ANPFSQR5
local natural history museum collections (University of Maine, College of the Atlantic [COA]) and the current NPS collection at Acadia National Park but could not locate these specimens and assume they no longer exist. Godin (1977: 102) examined two specimens from MDI for his treatise on mammals of New England and those specimens were listed as part of collections at either the Harvard or Smithsonian Natural History museums. In addition to the two northern flying squirrel specimens examined by Godin (1977) we know of only three other specimens from MDI. All specimens are currently in COA's museum collection (at the time of this report, however, one specimen was to be given to the Maine Audubon Society for educational purposes) in Bar Harbor, ME (35 mm slides of specimens in COA's collection are now on file at NPS offices in Bar Harbor). Although coincidental, for much ofthis century surveys have documented flying squirrels on MDI at about 10 year intervals (with slight exceptions). Despite documentation that has been inattentive from a purely scientific viewpoint, this chronology provides some basis from which to evaluate the local status of these arboreal rodents. In retrospect, voucher specimens would provide important information on the distribution of flying squirrels on MDI, particularly the existence ofvolans. Although collection of voucher specimens is standard in the conduct of most scientific studies, the issue can be emotional (Reynolds et al. 1996), and some agencies discourage the practice. Agencies that are reluctant to allow collection of voucher specimens should consider the value of scientific information in the context of monitoring biodiversity (Reynolds et al. 1996), an objective many consider critical for protecting natural resources. Past studies of the northern flying squirrel have concentrated on habitat characteristics in the Great Lakes Region and the southern Appalachians, where two subspecies,Juscus and coloratus, that occur in the mountains of Virginia and North Carolina are endangered (Weigl and Osgood 1974, Urban 1988, Payne et al. 1989, U. S. Fish and Wildlife Service [FWS] 1990). Many questions regarding the natural history of American flying squirrels remain to be answered (U.S. FWS 1990). In particular, the distribution of the southern species on MDI and elsewhere throughout southcentral Maine needs better documentation. Areas where the two squirrel species may overlap, like MDI, should receive periodic surveys to update the occurrence of these rodents, and if the southern species is found, additional research on the relationship between the two congeners seems warranted.
Recommendations
We recommend that the NPS periodically resurvey for flying squirrels at approximately 10 year intervals. Although work has been conducted only on southern flying squirrels (Witt 1992), these rodents have relatively low metabolism and rapidly lose heat. Trapping should stop when ambient temperatures fall below 7.00 C or precautions like nest material or boxes are employed. Trapping surveys should encompass more sites (than this survey), and periods should be two weeks, and longer if possible, to ensure capture of resident individuals. Because southern flying squirrels appear to be rare on MDI, if they exist at all, trapping surveys will need to be extensive to determine ifthis species occurs. Finally, we recommend collection of voucher specimens to effectively document biodiversity. ANPFSQR6
Acknowledgments
We wish to thank the Eastern National Association for their financial support of this project. The staff at Acadia National Park, particularly Bruce Connery, assisted with field work, as did Kimberly Meyer, Adam Vashon, Scott Whitcomb, Steven Richard, Gil Paquette, Eric York, and Kristine Higgins. Steve Garman gave constructive advice, reviewed the draft report, and shared his knowledge on small mammal trapping and we thank him. Dave Manski and Bruce Connery kindly reviewed and provided many helpful comments on the draft report, and somehow tolerated our delinquency in completing this effort, for that we will be forever grateful.
Literature Cited
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Table 1. Mean density (per ha) of trees (> 10.2 cm dbh) in 8 potential habitats for flying squirrels in Acadia National Park on MDI, ME.
Deciduous Conifer
Potential sites for northern flying squirrels Bubble Pond (conifer) 75 274 Beech Mountain (conifer)* 70 260 Sargeant Drive (conifer) * 17 185 Eagle Lake (conifer) 33 261
Potential sites for southern flying squirrels
Compass Harbor (mixed) * 115 58 Aunt Betty's Pond (hardwood)** 434 8 Bubble Rock (hardwood) 193 6 Sand Beach (mixed) 45 72
.) *: sites where squirrels were captured,;::::: 2 individuals **: only one individual captured ANPFSQRll
Table 2. Weights (g) for northern flying squirrels captured in Acadia National Park on MDI, ME. ANPFSQR12
Table 3. Capture rates (captures/lOO trap nights) for flying squirrels at 8 sites in Acadia National Park on MDI, ME.
INITIAL CAPTURES a TOTAL CAPTURES Adult Adult Juvenile Adult Adult Juvenile Capture Female Male ~ Female Male Rates Bubble Pond 0 0 0 ~ 0 0 0 0 Beech Mtna. 0 3 0 ~ 0 10 0 1.74 Sargeant Dr. 4 4 4 ~ 7 12 5 4.20 Eagle Lake 0 0 0 ~ 0 0 0 0 Compass Hbr. a 2 3 1 ~ 10 10 1 3.65 Aunt Betty's Pond 1 0 0 ~ 2 0 0 0.35 Sand Beach 0 0 0 ~ 0 0 0 0 Bubble Rock 0 0 0 ~ 0 0 0 0 a: Individuals captured at these two sites were initially marked with color dye that proved ineffective as a lasting mark. ANPFSQR13
Table 4. Comparison of habitat characteristics of sites with and without northern flying squirrel populations in Acadia National Park on Mount Desert Island, ME.
Sites with Squirrels (n = 3) Sites w/out Squirrels (n = 4) x SE x SE Conifer Tree 167.7 59.1 153.5 67.5 Density (#/ha) Deciduous Tree 67.3 28.2 86.4 36.6 Density (#/ha) Conifer Tree 13.4 1.0 13.7 1.2 Diameter (> 10.16 cm) Deciduous Tree 11.2 1.2 11.2 0.9 Diameter (> 10.16 cm)
Log Density 3.8 1.9 4.1 1.7 (#/ha) Snag Density 2.4 0.4 2.5 0.7 (#/ha) ANPFSQR14
Table 5. The mean number oflogs/ha and snags/ha for three sites where flying squirrels occurred (> 1 individual) and 4 sites where no squirrels were captured in Acadia National Park on MDI, ME. Log and snag categories taken from Thomas et al. (1979).
Transects with Squirre1s Transects w/Qut Squirre1s n x SE n x SE Log 1 3 0.6 0.2 4 0.8 0.4 2 3 0.6 0.3 4 1.6 0.6 3 3 7.8 2.9 4 6.3 1.3 4 3 6.2 3.3 4 7.7 1.4
5 3 1.7 0.6 4 3.0 1.0
Snag 3 3 3.2 1.3 4 1.6 0.8
4 3 2.0 0.8 4 2.1 0.9
5 3 0.9 0.4 4 0.4 0.3 6 3 3.2 1.3 4 4.1 1.0
7 3 2.9 1.7 4 4.2 0.7
8 3 0.1 0.1 4 0.4 0.2 ANPFSQR15
Table 6. Density (trees/ha) and Shannon index of species diversity for tree species> 10.16 cm dbh at eight sites in Acadia National Park, on MDI, ME.
Picea glauca 18.6 0.0 0.0 0.0 36.2 0.5 0.0 0.0
Picea rubens 21.5 149.5 186.6 0.0 12.4 66.4 5.8 176.2
Picea abies 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0
Picea spp. 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Abies balsamea 0.6 8.5 44.1 0.0 8.1 3.8 0.0 13.2
Tsuga cauadensis 3.5 12.5 12.4 0.0 0.3 0.9 0.8 14.0
Pinus strobus 8.9 1.5 2.3 6.9 3.3 44.5 0.0 13.8
Pinus resinosa 4.5 0.0 0.2 0.9 0.2 1.4 0.0 0.5
Pinus rigida 0.0 2.4 0.0 0.0 0.3 32.0 0.0 0.0
Acer rubrum 30.6 21.7 7.8 74.2 14.2 9.3 16.0 35.6
Acer 0.0 0.0 2.3 0.0 0.0 0.4 6.9 5.5 pennsylvanicum
Acer saccharum 0.0 0.0 0.1 0.0 0.0 0.0 20.1 0.0 Acer spp. 0.3 0.0 0.0 0.0 3.6 0.0 0.0 1.3
Quercus rubra 41.2 0.0 0.0 267.0 0.0 0.0 0.0 0.0 Fagus graudifolia 4.0 0.0 0.7 11.4 0.0 0.0 124.1 0.2
Betula papryifera 20.4 40.5 19.7 7.4 26.4 7.5 13.9 26.6
Betula 0.0 0.0 0.6 0.0 0.0 0.0 9.6 0.0 Alleghaniensis
Betula 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.8 populifolia
Thuja 0.0 85.8 15.4 0.0 10.9 35.7 0.0 57.2 occidentalis
Fraxinus 1.6 0.0 0.0 0.0 15.5 0.0 2.4 0.3 pennslvauica
Fraxinus spp. 11.2 0.0 0.0 0.0 2.6 0.0 0.0 0.0
Populus 5.1 0.0 0.0 0.0 75.4 0.0 0.0 0.0 tremulodies ANPFSQR16
0.0 0.4 0.0 74.3 23.0 3.6 0.0 4.3 Populus grandidentata
Malus spp. 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Prunus 0.0 0.0 0.0 0.0 3.3 0.0 0.0 0.0 virginiana
Carpinus 0.0 0.0 0.7 0.0 0.0 0.0 0.0 0.0 caroliniana
Lonicera spp. 0.0 7.4 0.9 0.0 0.0 0.0 0.0 0.0 ANPFSQR17
Table 7. Comparison of tree diameters and stem densities, mean (standard error), between trap sites where squirrels were captured compared to locations without squirrel captures in Acadia National Park on MD!, ME.
a Beech Mtn Sargeant Dr. a Compass Hbr.b Conifer I· ·Nttaptur~sl Capt I 12.3(0.4) 9.6(1.5)' 16.6(1.5) 16.0(1.0)' 12.6(1.1)
Small Tree 9.9(3.7)' 19.2(3.9)' 1.9(0.7)* 6.1(1.6)' 3.6(2.4) 2.1(1.1) 8.9(1.9) 4.9(1.2) Density
Sapling 2.3(1.0)* 6.9(1.5)* 1.4(0.6) 2.1(1.5) 1.0(0.6) 1.1(0.6) 0.6(0.6) 6.3(3.0) Density
Seedling 7.1(2.3) 6.4(2.2) 11.1(3.3)* 5.4(2.3)* 0.0(0.0) I 0.3(0.3) 0.4(0.4) 1.9(1.5)
a: Conifer stand b: Mixed-wood stand * Denotes difference between capture locations and locations without captures at p ,.; 0.10. ANPFSQR 18
Appendix A. Maps ofMDI, ME showing transect locations used to trap flying squirrels and sample vegetation during 1992. . ) IlQ] Flying squirrel transects [ZQ] Primary & secondary roads lZQ] Tertiary roads lZQ] Quaternary roads lZQ] Carriage roads /\/ Tr ai Is '---- II Lakes and ponds II Northern hardwoods • Red oak ( ~ Red maple om Birch/aspen forest ~ Mixed hardwood/conifer ~ Mixed conifer Spruce/fir Sea e 1:6000
Key to close-up transect maps /' ~) \
General locations of transects on Mt. Desert Island ~ Approximate location of 1947 fire
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o
General locations of transects on Mt. Desert Island l
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Flying squirrel trapping transects: Aunt Bettys Pond (
Flying squirrel trapping transects: Beech Cliff Trail I Flying squirrel trapping transects: Compass Ha~dJ -91
I I I I I
Flying squirrel trapping transects: Sand Beach Flying squirrel trapping transects: Sargent Drive )
Flying squirrel trapping transects: Eagle Lake Flying squirrel trapping transects: Bubble Rock Flying squirrel trapping transects: Bubble Pond