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Chronic browsing by Odocoileus virginianus (White-tailed Deer) has potential to alter the life history of trees within Mid-Atlantic forests, including seedling size and abundance in the short term to overstory composition in the long term. Most studies quantify the effects of deer browse using small plots (<1 ha) and short time frames (<10 years), which may misrepresent larger-scale and longer-term impacts. We maintained a 4-ha deer exclusion plot for 20 years in a mesic northern Virginia temperate deciduous forest to examine the impacts of browsing on forest trees at multiple life-history stages. We compared the abundance and species composition, as well as seedling height, of woody stems across the seedling, small-sapling, and large-sapling size classes inside the deer exclosure and within an adjacent reference area. There were no significant differences in seedling abundance or community composition, but seedling height was on average 2.25 times greater in the exclosure than the reference plot. Small-sapling (1–5 cm DBH) stem count was 4.1 times greater inside the exclosure, with all species more abundant in the exclosure except Asimina triloba (Pawpaw) and Carya tomentosa (Mockernut Hickory). Differences were smaller in the large-sapling size class (5–10 cm DBH), with relative total large-sapling stem count only 1.25 times greater in the exclosure. Browsing pressure appeared to influence the composition and size structure of smaller stems in the past 20 years, but has had little effect on larger stems. While the lack of replication limited the scope of inference of our study, our findings suggest that natural delays in mature tree recruitment in a closed-canopy forest may mask the full impact of deer herbivory for decades.
Management strategies for Odocoileus virginianus (White-tailed Deer) often use changes in body weight as an indicator of population health and density. Annual fluctuations in White-tailed Deer age-sex classes are influenced by numerous environmental variables. We analyzed 1989–2009 deer harvest data from Virginia's Deer Management Assistance Program (DMAP), consisting of 15,622 deer in the Northern Piedmont of Virginia. We used Pearson's correlation and t-tests to examine impacts of annual fluctuations in precipitation, days with snow accumulation ≥1 inch, temperature, and acorn mast on average weights (kg) of current-year, 1-year-lag, and 2-year-lag fawn, and yearling age-sex classes. Of the variables we examined, seasonal precipitation appears to be the most significant environmental factor influencing White-tailed Deer body weight in the Northern Piedmont of Virginia. When using deer weight fluctuations as an indicator in management plans, managers should consider the influence of seasonal precipitation specific to their geographic region or management unit. Managers in the Northern Piedmont of Virginia should continue to use changes in average deer weights as an indicator of population density and habitat quality due to the stability of weights in response to regional environmental stochastic events.
The invasive crab Hemigrapsus sanguineus (Asian Shore Crab) arrived on the northeast coast of the United States about fifteen years ago, and has attained high population levels at the expense of other resident crabs. Data collected between 1998–2012 at a low-energy, rocky intertidal site in the western Long Island Sound reveal continued Asian Shore Crab dominance. A body of research has suggested several reasons for the success of the Asian Shore Crab, including predation on resident crabs. We coupled morphometric data with measurements of claw closure force to model strength as a function of crab size and sex, enabling interspecific comparisons. The model provides indirect support for conclusions of an earlier study that suggested Asian Shore Crab dominance was achieved through predation on juvenile recruits of resident crabs such as Carcinus maenas (Green Crab). Asian Shore Crab males may have had more impact than females on Green Crabs due to the sexual dimorphism of Asian Shore Crab chelae and consequent strength disparity.
While conducting an on-going project investigating the effects of prescribed fire on reptile communities, 31 Terrapene Carolina Carolina (Eastern Box Turtle) were captured in burned and unburned study sites; some with extensive injuries that were likely caused by a recent prescribed burn. In order to determine if the disturbance had any negative effects on the turtles, we recorded morphometries, mass, sex, and injuries for each one captured. Twenty percent of box turtles in the burned area exhibited injuries caused by the fire. Turtles in burned sites were similar in length but weighed significantly less (df = 1, F = 5.255, P = 0.0329) and had a poorer body-condition index than turtles in unburned sites. Additionally, one injured box turtle was encountered 32 times in a burned site. On average, this individual moved 22.5 m/day within a 3.77 ha home range. Over the course of 1 year, the turtle grew 1.3 mm and gained 27 g. The injuries to the carapace of this individual never fully healed during that year, and the scutes did not grow back; however, regeneration of the carapace may require a longer period of time. These scant data suggest that Eastern Box Turtles may not respond favorably to prescribed fire, and indicate that additional studies are needed to increase knowledge of the effects of prescribed fire on this species.
Mya arenaria (Softshell Clam) inhabit a wide range of intertidal and subtidal sediment types in the western North Atlantic. They avoid predation by burrowing deeply in the sediment. We investigated the effect of sediment type on the antipredator responses of Softshell Clams to Carcinus maenas (Green Crab) as well as the relative costs and benefits of living in different sediment types. Clam burrowing depth, growth, and Green Crab predation rate were observed in experimental plots of mud, sand, and gravel. Clams exposed to crabs burrowed deeper than did control clams in all sediment types, but clams burrowed deepest in finer sediment types. Clams in coarser sediments also had thicker shells and suffered lower rates of predation than did those in mud. These results suggest distinctive costs and benefits associated with inhabiting different sediment types. For Softshell Clams, coarse sediments are most costly metabolically, but have lower predation risk compared to finer sediments.
Procyon lotor (Raccoon) is a major predator of beach-nesting and colonial waterbirds on the Virginia barrier islands. An understanding of water as a barrier to inter-island movement by Raccoons will be essential to effective management of these predators in this naturally fragmented coastal environment. We examined 4 independent lines of direct evidence for Raccoon movement between 1999 and 2007: 1) locations of recaptured, ear-tagged Raccoons on both the islands and the adjacent mainland, 2) overland movements of radio-collared Raccoons, 3) inter-island movements of radio-collared resident Raccoons, and 4) movements of translocated Raccoons. We recaptured 78 of 177 ear-tagged island Raccoons, all on the same island as the initial capture. We also tagged and released 65 mainland Raccoons, none of which was ever recaptured on an island. We often observed overland movements >1 km per day by radio-collared animals on both the islands and the mainland. Nevertheless, only 3 of 51 (6%) collared animals (2 males and 1 female) moved overwater from the location where they were captured. None of the 4 Raccoons radio-collared on the mainland moved to an island. Although Raccoons in this system are highly mobile, overwater movements seem to be infrequent events; only 3 of 234 tagged/ collared island individuals moved between islands, and none of the 69 tagged/collared mainland individuals moved to an island. Finally, we observed return movements by 22 of the 32 (69%) animals (11 males and 11 females) that were translocated either from the mainland to a nearby island or between adjacent islands. Translocated animals exhibited a much greater tendency than resident animals to make overwater crossings. In all cases of overwater movement, the water channels were relatively shallow and relatively slow moving. None of the 335 marked animals in this study crossed a tidal inlet. The mobility observed here is consistent with the idea that the distribution of Raccoons on the islands has expanded in recent decades. Predation management on these islands will require a strategic approach that takes into account both island isolation and Raccoon mobility.
We provide a preliminary assessment of the ground-dwelling arthropod community composition in six common coastal dune ecosystem land cover-types at Cape Cod National Seashore. We captured 6815 individual arthropods representing 16 arthropod orders from 1008 terrestrial pitfall trap-nights. The most abundant orders were Hymenoptera, Diptera, Araneae, and Isopoda (76.1%, 8.5%, 5.5%, and 3.3% of total captures, respectively). There were differences in ground-dwelling arthropod community composition among the three early-successional and the three later-successional cover types, with the latter having a greater overall arthropod diversity and higher capture rates for a number of the major arthropod taxa captured. Our report is among the first communitywide analyses of arthropod community composition in coastal dune ecosystems of the northeastern US. The results from this study should be viewed as a preliminary assessment given that: 1) we employed a single trapping method (i.e., pitfall traps); 2) traps were only open during the late-afternoon to early morning hours, and only during the summer months; and 3) captured arthropods were classified only to order. We hope our report will inspire additional research of coastal dune arthropod communities.
In North America, Castor canadensis (Beaver) impoundments of low-order streams greatly modify ecological processes, influence stream biota, and impact fish movement. We evaluated the short-term effects of removing a beaver dam from an Appalachian headwater stream on a Salvelinus fontinalis (Brook Trout) population. Prior to dam removal, we found only one marked trout that had navigated the dam moving upstream and no marked trout from above the dam moving downstream. Immediately following dam removal, trout abundance above and below the dam increased 67.1% and 46.0%, respectively. During later samples, however, declines in both trout abundance and relative weight suggest the initial large increases in our study sections after dam removal may have led to increased competition among trout, causing large numbers to move several hundred meters further upstream, beyond our study site, in order to find acceptable habitat. These results demonstrate that the presence and subsequent removal of a beaver pond on a Brook Trout stream can be considered both beneficial and harmful; thus, site-specific evaluation is necessary to determine best whether to retain or remove ponds.
This paper presents the results of a long-term study to detect the presence of Puma concolor (Cougar) in eastern Canada. We installed 38 scratching posts to attract wild Cougars and collect hair samples in several national and provincial parks in Québec, New Brunswick, and Nova Scotia. A set of semi-nested primers was used to discriminate Cougar samples from other mammalian species based on variation in the 16S rRNA gene of the mitochondrial DNA. Our analyses performed on 476 hair samples revealed 19 positive identifications of Cougars in Québec and New Brunswick. Sequencing further showed that some specimens were from South America, whereas others had a North American origin. We discuss the implications of these results for the conservation of Cougars in eastern Canada.
Woodland vernal pools, small-scale forested depressions that flood in the spring and dry as summer progresses, are an essential and rapidly disappearing component of breeding habitat for numerous amphibian and macroinvertebrate species. Here we propose five multiple linear regression models to assist in the rapid assessment of vernal pools to conserve those with the greatest amphibian, aquatic macroinvertebrate, and herbaceous vegetation features. These models are based on samples taken from 21 pools distributed throughout the South Mountain landscape, a largely forested landscape matrix in south-central Pennsylvania. A comparison of the vegetative community of vernal pools and upland sites using Morisita's index of community similarity shows them to be quite distinct. Based on our analyses and models, we propose conserving woodland vernal pools that possess plant species indicative of seasonal inundation, a large water volume when inundated, high tree cover, presence of coarse woody debris, high phosphate level in the water, and low sphagnum presence along the pool perimeter. Vernal pools with high herbaceous, shrub, and tree diversity likewise predict high amphibian productivity (abundance). This rapid assessment is expected to be a set of invaluable tools for identifying and ranking woodland vernal pools for state and federal conservation agencies.
Spiders are often found as residents in association with Sarracenia purpurea (Purple Pitcher Plant). Many spiders choose web locations based on environmental cues such as vegetation structure and composition, prey density, temperature, and humidity. To determine if spiders use cues from the Purple Pitcher Plant to build their webs, we conducted a field study using variants of the plant that separated various morphological features: nectar, pigment, and the presence of prey. There was no difference in spider residency across all treatments and no difference in male/female or mature/immature residency. Linyphiids were the most common residents, possibly due to pitcher structure and natural web size.
Disseminated neoplasia, a diffuse tumor of the hemic system, is characterized in many bivalve mollusks by hemolymph containing 1–100% mitotic hemocytes. Little is known about the onset and chronic distribution of neoplasia in populations of Mya arenaria (Soft-shell Clam), though studies have reported episodic exposure to environmental contaminants or an infectious agent as a potential cause of this disease. Here we provide the first set of continuous data on neoplasia in Soft-shell Clams, from three sites in New England where sediments have been characterized regarding their granulometry, composition, contaminants, and clam densities. When correlating sediment characteristics to terminal neoplasia (76–100% neoplastic or rounded, unattached hemocytes), New Bedford Harbor, MA, which is the most contaminated site, had the highest frequency of treminal neoplasia (maximum of 9.49% ± 0.78 SE), and the most pristine site, Ogunquit, ME, displayed the lowest frequencies (maximum of 0.47% ± 0.05 SE). Correlations of frequency of neoplasia to known environmental contaminants also suggests that fully neoplastic individuals were found only at sites of increased levels of heavy metals, PCBs, and PAHs. In addition, we documented the highest frequency of clams with terminal neoplasia from New Bedford Harbor in December (9.49% ± 0.78 SE) when seawater temperatures were low, and the lowest frequency in July (1.08 ± 0.4 SE) when seawater temperatures were highest. These results may indicate vulnerability of neoplastic clams to seasonal increases in environmental temperature and resulting oxidative stress. Based on shell measurements and a theoretical mathematical age model (which correlates susceptibility to neoplasia with age and sexual maturity), we suggest that the Soft-shell Clam is most susceptible to this disease between one and two years of age (9.5% frequency at 1 year, 22.25% incidence at 1.5 years, and 57.14% incidence at 2 years).
Collections of bird specimens are an important resource for teaching bird identification, but acquiring suitable specimens can be problematic. Older collections tend to be preserved with a variety of potentially harmful chemicals; additionally, traditional methods for preparing specimens typically require extensive training. Freeze-drying is a method that involves removing water from specimens via sublimation, and may be an acceptable alternative to conventional taxidermy techniques for teaching collections. We freeze-dried 63 birds and 12 bird parts (i.e., talons and wings) of 44 species salvaged from throughout Pennsylvania since January 2008 using a Taxi-Dry Freeze-Dryer (Freeze-dry Specialties, Inc.). To determine the extent of water lost during the freeze-drying process, we measured the masses of birds and parts before and after preservation. Whole birds that were successfully freeze-dried lost 59.4% ± 0.9% (mean ± SE) of their initial mass, and unsuccessfully dried birds lost 46.9% ± 3.5% of their initial mass. Generally, birds with an initial mass >160 g did not lose enough water in the freeze-drying process to be effectively preserved. We conclude that if proper storage and maintenance conditions are met, freeze-drying can be an effective method for preserving small bird specimens for teaching collections.
Evidence for the presence of the native philomycid slugs Philomycus carolinianus (Carolina Mantleslug) and Megapallifera mutabilis (Changeable Mantleslug) in Wisconsin is given through data on body length, external morphology, traits of the jaw, color pattern, genital morphology, and comparison to the known distribution data for members of the genera. These are the first published records from Wisconsin for these two species.
We report 4 new recoveries of the endangered Myotis sodalis (Indiana Bat) that were banded in Michigan during summer and found hibernating in Ohio, Indiana, or Kentucky, 225–386 km from the initial banding site. A fifth individual apparently made the longest migration on record for Indiana Bats (575 km) on multiple occasions. Since 1997, 15% of 71 Indiana Bats banded in Michigan during summer have been recovered during winter.