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Heavy predation by Mergus merganser (Common Merganser) during severe winters of 2013–2014 and 2014–2015 resulted in substantial reductions of wild Salmo trutta (Brown Trout) in open-water, groundwater-fed reaches of Oatka Creek in western New York State. New York State Department of Environmental Conservation considered the need for habitat manipulation to reduce the severity of future overwinter-predation by mergansers in Oatka Creek Park (OCP) but lacked data to make an informed decision. Thus, this study sought to estimate population abundance, density, and year-class distribution of Brown Trout; quantify the availability of cover and habitat; and identify habitat features used by Brown Trout in OCP. We recorded data for 100 Brown Trout (101–512 mm TL) during spring 2016, autumn 2016, winter 2017, and spring 2017. Despite the absence of mergansers in ensuing warmer winters, trout population indices decreased as the study continued, likely affected by high streamflow during sampling events. Year-class distributions typical of a small stream, however, suggest that the population is recovering. Velocity refuges and structural cover were the primary factors determining habitat selection. Large woody debris was the most favored cover type by all Brown Trout; however, boulders were also important, especially during low streamflow. Large trout (>300 mm) showed a strong preference for deepwater habitats with slow currents and high densities of woody debris and boulders, while small trout (<200 mm) preferred shallower complex habitats with slow currents, course substrates, and high cover densities. Quality trout habitat and instream cover is abundant throughout OCP, but the abundance of highly complex overwinter habitats capable of providing protection from mergansers may be limited. Adding complex structural cover to areas favored by smaller trout (<300 mm) could increase habitat complexity and likely reduce the severity of future overwinter predation.
Biodiversity hotspots are regions with high numbers of rare species that are conservation priorities. Hall's Gullies is a region on the Avalon Peninsula in Newfoundland, Canada, that is well known for a large population of Erioderma pedicellatum, a lichen that is listed globally as critically endangered by the International Union for Conservation of Nature. To determine if there are other species of conservation interest in this region, we completed a detailed survey of the lichens and allied fungi. We combined our results with historical collections and report 179 species in 86 genera, which include 18 cyanolichens and 20 calicioids. Three species are listed on the federal Species at Risk Act: Degelia plumbea, Erioderma mollissimum, and E. pedicellatum. Fifteen species discovered during our study were new to Newfoundland and Labrador. Eleven of those species (the calicioids) we reported in a previous publication, but 4 are reported here for the first time from the province: Abrothallus santessonii, Biatora chrysantha, Heterodermia neglecta, and Plectocarpon scrobiculatae. Hall's Gullies is a hotspot for rare lichen species, but it is not legally protected and, as a result, should be a conservation priority.
Physiological states in snakes, such as digestion, gestation, and ecdysis, have been associated with different body temperatures (BT), yet few studies have examined these associations in a comparative context for wild-caught animals. We collected body and environmental temperatures for 2 natricine snake species—Thamnophis sirtalis (Common Gartersnake) and Nerodia sipedon (Common Watersnake)—from 4 artificial wetlands at the Letterkenny Army Depot, Franklin County, PA. We measured thermal data and associated microclimates from snakes captured under tin cover boards during monthly searches from Spring to Fall of 2012 (April–October). From 47 Common Gartersnakes and 20 Common Watersnakes, we found that most individuals of both species had a BT between 20 and 30 °C, which is consistent with data from other populations. Inter- and intraspecific comparisons of snake BTs in different physiological states revealed that Common Gartersnakes operated at higher temperatures than Common Watersnakes. Common Watersnakes thermoregulated within a generally narrower range of temperatures than Common Gartersnakes. The wide-ranging thermal ecology of the Common Gartersnake may facilitate its flexibility to occupy many habitats across an extensive geographic distribution and perhaps predispose it to greater adaptability in a changing thermal environment. We summarize our data on snake BTs and their associations with relevant environmental temperatures, discuss snake BT ranges across distinct physiological groups, and compare our results to those of other snake populations. Our findings provide a baseline to understand the degree to which operating snake temperatures, and consequently physiological processes, will change because of future warming in the Northeast.
Invasive species pose a considerable threat to biodiversity and the functioning of the ecosystem. Hemigrapsus sanguineus (Asian Shore Crab) has outnumbered native crabs on the northeast coast of North America since shortly after its introduction in the late 1980s. Asian Shore Crabs occur in high densities along much of the Atlantic coast from Maine to North Carolina. Our research focused on the relationship between limb loss and energy use and storage in both male and female Asian Shore Crabs as a means of understanding their ability to reach high population densities. We sampled 154 crabs of both sexes from Odiorne Point State Park in Rye, NH. We then dissected the individual specimens and measured limb loss and the mass of the hepatopancreas (an energy storage organ) and gonads. Our findings reveal that limb loss has similarly limited impacts on male and female crabs in terms of both energy storage and reproductive effort. We conclude that despite a high frequency of injury, the energetics of Asian Shore Crabs were largely unaffected, and that this may be one reason why this species has been able to achieve sustained high densities throughout much of its invaded range.
A few moderately long-term studies have documented population dynamics of the invasive Hemigrapsus sanguineus (Asian Shore Crab) and species with which it interacts. One such study on Cape Cod reported exponential growth of the Asian Shore Crab through 2012, concurrent with declines in 2 resident species, but recent data at nearby sites suggest considerable geographic variation in population dynamics, with modest recovery of resident crab populations. We monitored the Cape Cod population for an additional 5 years to determine whether population growth of the Asian Shore Crab had slowed and whether there was any change in population dynamics of Carcinus maenas (Green Crab), Littorina littorea (Common Periwinkle), or Mytilus edulis (Blue Mussel). Asian Shore Crab density declined by nearly 90% since 2012. There was no evidence of recovery by the Green Crab, but the Blue Mussel experienced a brief but substantial increase in density in 2015, when both crab species displayed >70% reductions in density from the previous year. The pattern of population dynamics of the Asian Shore Crab from 2003 to 2017 is consistent with boom–bust dynamics, but it remains unclear whether the population will equilibrate near its current density or undergo recurrent boom–bust cycles.
According to the transparency-regulator hypothesis (TRH), water transparency is the main driver of zooplankton diel vertical migration (DVM) because it influences ultraviolet radiation (UV) exposure and visual predation, which vary greatly over a diel period. I tested the TRH by examining zooplankton DVM and Secchi depth over 2 summers in Mountain Lake, VA, a unique natural lake where transparency and water level fluctuate substantially. Daytime mean depth and Secchi depth were positively correlated for Daphnia parvula, but this was not the case for other taxa. Zooplankton exhibited diurnal deficits (DDs; higher night densities compared to day), indicating that DVM does not account for all diel movement. DDs are sometimes attributed to light-mediated sampler avoidance or diel horizontal migration (DHM), but DDs did not increase with Secchi depth and DDs in littoral zones do not indicate DHM. Overall, these results suggest that factors other than transparency—perhaps predator densities—more strongly influence DVM in Mountain Lake.
In our air pollution studies at The Pennsylvania State University, we have successfully used Prunus serotina (Black Cherry), Asclepias syriaca (Common Milkweed), Apocynum androsaemifolium (Spreading Dogbane), and Ailanthus altissima (Tree-of-Heaven) as ozone-sensitive bioindicators to detect phytotoxic levels of ambient ozone. However, ambient ozone concentrations have decreased in our study area, and we are seeking a more sensitive bioindicator species. We observed significant levels of ambient ozone-induced leaf injury (stipple) on native Rhus typhina (Staghorn Sumac) within a field in a central Pennsylvania, suggesting that this species might serve as a new and highly sensitive ozone bioindicator. Therefore, we conducted a preliminary survey to determine the incidence and severity of ozone-induced stipple on Staghorn Sumac. In the same location, we concurrently evaluated the level of foliar stipple on the ozone-sensitive bioindicator species listed above. Staghorn Sumac developed significantly greater ozone-induced symptoms than the other bioindicators and has potential to serve as a bioindicator to detect phytotoxic levels of ambient ozone in the eastern US.
Shrimp are critical to estuarine food webs because they are a resource to economically and ecologically important fish and crabs, but also consume primary production and prey on larval fish and small invertebrates. Yet, we know little of their natural history. This study determined shrimp community composition, seasonality, and life histories by sampling the water column and benthos with plankton nets and benthic traps, respectively, in Great Bay, a relatively unaltered estuary in southern New Jersey. We identified 6 native (Crangon septemspinosa, Palaemon vulgaris, P. pugio, P. intermedius, Hippolyte pleuracanthus, and Gilvossius setimanus) and 1 non-native (P. macrodactylus) shrimp species. These results suggest that the estuary is home to a relatively diverse group of shrimp species that differ in the spatial and temporal use of the estuary and the adjacent inner shelf.
Setophaga discolor (Prairie Warbler) is a Nearctic–Neotropical migratory songbird that is experiencing long-term population declines. A potentially important driver behind these decreases is the loss of shrubland and early successional forest communities in the eastern United States. Central to conservation for species like the Prairie Warbler is an understanding of breeding habitat requirements at the scale of the home range. Despite the Prairie Warbler being identified as a species of continental conservation concern, few studies have explicitly quantified habitat conditions within its home ranges. We used radio telemetry to quantify Prairie Warbler use of space during the breeding season as well as associated vegetation data across 3 study sites in north-central Pennsylvania from May to June 2016. We radio-tracked 11 adult male Prairie Warblers. Using the telemetry locations, we estimated kernel densities and classified minimum convex polygons around kernel densities to define males' home ranges and core-use areas. The average home range (95% kernel) was 6.4 ha, and the average core-use area (50% kernel) was 0.73 ha. Prairie Warbler core-use areas contained more shrubs and lower tree count than peripheral portions of home ranges. To this end, management activities that promote a dense shrub layer across early successional communities should benefit Prairie Warblers. Results from this study serve as baseline data that can be used to help direct future studies at the home-range scale of Prairie Warbler breeding-season ecology.
We examined the predator–prey relationship between nymphs of the predatory dragonfly Anax junius (Common Green Darner) and larval and metamorphic Notophthalmus viridescens (Eastern Newt), some of which may contain the potent neurotoxin, tetrodotoxin. First, we conducted a palatability study to determine which life-history stages were palatable to dragonflies. We also tested the metamorphosis and survival rates of larval newts when exposed to predatory dragonflies in small microcosms. Finally, we tested the predator avoidance behavior of larval newts in response to chemical cues from a control, food stimulus, and predatory dragonflies. All life-history stages (small and large larvae, and recent metamorphs) were palatable to dragonflies. In microcosm trials, we found that newt larvae had a lower chance of surviving and transforming when dragonflies were present compared to a control. Finally, newt larvae decreased movement significantly when exposed to predatory dragonfly stimulus compared to either a control or food stimulus. These results suggest dragonflies are effective predators of newts from hatching through metamorphosis. However, the larvae do possess behavioral avoidance mechanisms that likely reduce the risk of predation by dragonflies.
Although bats are highly transient and secretive animals, banding allows biologists to track the longevity of these mammals and their return rates to various roosts. For its mass, Myotis lucifugus (Little Brown Bat) is extremely long-lived, with multiple records exceeding 30 y of age. We report 9 longevity records from 5 male Little Brown Bats, found during hibernation in northwest Wisconsin, that were at least 18–32 y of age at the time of recapture. Extreme longevity records, like those reported here, may no longer be discovered, due to an introduced fungal disease, white-nose syndrome, that has caused mass mortality in species of hibernating bats in North America.
Although most summaries of the distribution of Neotoma magister (Allegheny Woodrat) do not include Massachusetts, there are 2 historical reports of the species' past occurrence there. Herein, we review those reports and provide details on a specimen from the Berkshire Mountains taken in 1958. No additional observations have been documented in Massachusetts over the subsequent 60 years. Recent efforts to confirm presence of woodrats at the Berkshire Mountains site and efforts in the past several decades to locate a population elsewhere in Massachusetts have been unsuccessful. We conclude that the Allegheny Woodrat historically occurred in Massachusetts, although available habitat was limited. Based on the available habitat and the documented patterns of decline in other portions of the Northeast, it is almost surely now extirpated from Massachusetts.
A postflexion (tholichthys-stage) Chaetodon ocellatus (Spotfin Butterflyfish) was captured in a Southern Maine estuary in October 2017. As the Gulf of Maine continues its current warming trend, we anticipate an increase in the presence of such transient tropical species.
During a study of Canis lupus (Gray Wolf or Wolf) ecology on Michipicoten Island, ON, Canada, we observed the pelt of a Castor canadensis (American Beaver) within the natal chamber of a Wolf den. Herein, we describe this seemingly novel observation and discuss potential implications for denning Wolves.