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Didelphis virginiana (Virginia Opossum) continues to spread further north into temperate North America, raising questions regarding how they survive harsh winters. Very few marsupials exhibit winter adaptations such as torpor or seasonal molting. We used stable isotopes to evaluate evidence of seasonal molting in Opossums. We serially cut hairs from captive Opossums to determine if a documented diet shift early in life was reflected along the hair shaft. Isotope values along the hair mirrored a shift in captive Opossum's diets. We compared isotope values between Opossums trapped in different seasons and found no differences. The data indicate Opossums do not seasonally molt at the northern edge of their range.
Ant communities are an important component of ecosystem functioning, as ant activities often accelerate leaf-litter decomposition and nutrient cycling in forest soils. In Northeastern North America, global climate change is expected to accelerate forest succession, and the effects of this succession on forest ant communities remain relatively unexplored. This work aims to understand the effects of forest succession and productivity on the functional group diversity of New England ant communities by testing a prediction of species–energy theory. Our study took place at the Harvard Forest, MA, where we conducted localized ground surveys for ants and measured the productivity of 4 tree species dominant in New England. We found that both ant species richness and functional group richness were significantly higher in association with deciduous trees compared to coniferous tree types. Species richness and functional group richness were highly correlated. Contrary to the species–energy theory, we found no strong correlations between tree productivity and ant community composition or function. Our findings indicate that local, top-down forest processes may influence the composition and functioning of ant communities as New England forests become dominated by deciduous trees.
Biofilm forms the base of food webs as an autochthonous resource in nutrient-poor, heavily shaded headwater streams. However, we know little about the influence of bottom-up and top-down controls on the standing stock of biofilm biomass in headwater streams. We used spatially extensive stream surveys and pre-existing stream chemistry data to assess the influence of potential bottom-up and top-down controls of biofilm biomass in the oligotrophic headwater streams of the Hubbard Brook Experimental Forest (HBEF), NH. The potential bottom-up controls we considered were canopy cover and aspect (determinants of available radiation at the stream surface), available nutrients (e.g., nitrogen, phosphorus), physical habitat characteristics (e.g., stream width, substrate), and physicochemical properties of water (e.g., water conductivity, pH). The potential top-down controls we examined were benthic macroinvertebrate biomass and stream salamander occurrence. Salamanders may affect biofilm biomass indirectly by preying on benthic macroinvertebrate consumers. We used stepwise multiple linear regression to assess the relative importance of these variables in predicting biofilm biomass and found that biofilm increased with light availability (as indicated by canopy cover and aspect), nutrient availability, and lower acidity, suggesting that the autotrophic components of biofilm may be particularly important. Our top-down control indices were unrelated to biofilm biomass; however, more intensive studies on top-down controls are needed in these systems.
Evidence indicating a decline in Ondatra zibethicus (Muskrat) populations in the United States during the past 40 years has led to speculation regarding factors influencing Muskrat survival. In order to understand population dynamics and survival, it is important to first define the ecology of local populations. We investigated the dwelling structure use, movements, home range, and survival of radio-tagged Muskrats (n = 14) in an urban wetland complex in central Pennsylvania. We used locations collected from intensive radio-telemetry monitoring to determine number of lodging structures used, hourly movement, and size and percent area overlap of home ranges. Muskrats shared an average of 9 lodging structures, and on average, 68% of a Muskrat's home range overlapped home ranges of other Muskrats. We used 4 home-range estimators (kernel density estimator [KDE]href, KDEad hoc, KDEplug-in, and local convex hull estimator) to assess the ability of each estimator to represent Muskrat home ranges. The KDEplug-in that constrained the estimate of home range to habitat boundaries provided the most appropriate home-range size for Muskrats in a linear–non-linear habitat matrix. We also calculated overwinter survival estimates using known-fate models. Our top model indicated a positive effect of the average weekly precipitation on survival, with an overwinter survival estimate of 0.59 (SE = 0.16). The main cause of Muskrat mortality was predation by Neovison vison (American Mink; n = 6). The small sample size and uncertainty surrounding our model selection led to weak estimates of survival; however, our model suggests that snowfall may be an important factor in Muskrat survival. Our study provides novel data on Muskrat ecology in Pennsylvania as well as preliminary evidence for future investigations of factors affecting Muskrat survival during the winter months.
Productivity of Gavia immer (Common Loon) has declined in Ontario and across southern Canada. Variations in the timing of lake ice-off have the potential to negatively influence productivity of Common Loons, but there is conflicting evidence as to how ice-off dates affect this species' reproductive success. Our study investigated the association between annual ice-off timing in southern Ontario and the presence and reproductive success of Common Loons surveyed at 69 small lakes in 16 years over a 38-year span (1982–2019). We found negative relationships between residual ice-off date and the presence of Common Loon pairs, the proportion of Common Loon pairs attempting to breed, and the number of large young per pair per year, suggesting that there were fewer pairs, breeding attempts per pair, and large young per pair in years with later ice-off dates. Our results show that ice-off date is an important factor affecting reproduction in Common Loons, and that ice-off dates can be used to help predict annual variations in productivity of Common Loons.
During four 5-day trips to the 3 northern-most Maine counties of Aroostook, Piscataquis, and Somerset, we captured 347 small mammals from which we collected 415 fleas, 36 lice, and 10 larval botfly ectoparasites. Additionally, we located records of fleas from Maine in the Traub collection at the Carnegie Museum of Natural History, Pittsburgh, PA. From these sources, we establisned new state records of occurrence in Maine for 2 flea species, Conorhinopsylla stanfordi and Orchopeas howardi, and 1 louse species, Neohaematopinus semifasciatus. We herein report 27 new county records for fleas and 3 for botflies. The total number of flea species known to occur in Maine is now 32.
Risk associated with predation influences habitat selection in Odocoileus virginianus (White-tailed Deer). In the absence of predation risk, selection pressure for predator avoidance behaviors are relaxed, but behavioral traits associated with predator avoidance often persist. Our study area lacks populations of typical predators of White-tailed Deer, and our objective was to investigate birth-site selection by parturient White-tailed Deer in the absence of predation risk. We paired observed birth-sites (n = 31) with random sites and compared the vegetation characteristics using univariate paired analyses. Females selected birth-sites with 10% more vegetation density up to 1 m in comparison to random sites (P = 0.02). Parturient females have retained some degree of selection towards predator avoidance behavior despite the absence of non-human predator communities in the study area.
Haliaeetus leucocephalus (Bald Eagle) is a well-studied species, and information on their nest abundance and population trends is widely available. However, research on the movements and home range of nesting Bald Eagles in the interior US is lacking. In this study, we used a solar-powered Argos platform transmitter terminal (PTT) with global positioning system (GPS) capabilities to monitor the movements of an adult, breeding male Bald Eagle, captured at Ballard Wildlife Management Area, KY, from 29 April 2012 to 23 October 2013. We generated minimum convex polygons (MCP) for comparisons to previous studies and used 95% and 50% fixed kernel density estimators (KDE) to estimate home-range size and core-use areas, respectively, during nesting and non-nesting periods. Estimates of home range and core-use areas were slightly larger during the non-nesting period (MCP = 420.0 km2, 95% KDE = 1.6 km2, 50% KDE = 0.2 km2) when compared to the nesting period (nesting MCP=415.0 km2, 95% KDE =1.3 km2, 50% KDE = 0.01 km2). Our home range and core-use estimates were smaller than previous studies using comparable methods, suggesting that habitat quality at this site may be high.
A maternity roost for Lasionycteris noctivagans (Silver-haired Bat) discovered in Fredericton, NB, on 30 June 2020 is the first evidence of parturition for the species in Atlantic Canada and the most northern in eastern North America. The colony consisted of 17 non-volant pups and an estimated 8–10 adult females, with parturition estimated as early to mid-June. The roost was located at a height of ∼9 m in a mature Pinus strobus (Eastern White Pine). There is a need to assess the importance of large trees and stands of over-mature forest for bats in the Atlantic region.