Torpor and activity in a free-ranging tropical bat: implications for the distribution and conservation of mammals?

Bats are most diverse in the tropics, but there are no quantitative data on torpor use for energy conservation by any tropical bat in the wild. We examined the thermal biology, activity patterns and torpor use of two tree-roosting long-eared bats (Nyctophilus geoffroyi, 7.8?g) in tropical northern Australia in winter using temperature telemetry. Bats commenced activity about 20?min after sunset, ended activity about 2.5?h before sunrise and entered torpor everyday in the early morning even when minimum ambient temperatures (T _a) were as high as 23°C. On average, bats remained torpid for almost 5?h, mean minimum skin temperature (T _skin) measured was 22.8?±?0.1°C and daily T _skin minima were correlated with T _a. Our study shows that even in the tropics, torpor is frequently employed by bats, suggesting that worldwide most bat species are heterothermic and use torpor for energy conservation. We propose that the ability of employing torpor and the resulting highly plastic energy requirements may partially explain why these small insectivorous bats can inhabit almost the entire Australian continent despite vastly different climatic and likely trophic conditions. Reduced energy requirements also may permit survival in degraded or modified habitats, reduce the need for foraging and reduce exposure to predators. Thus, the ability to employ torpor may be one important reason for why most Australian bats and other heterothermic mammals have not gone extinct whereas many obligatory homeothermic mammals that cannot employ torpor and have high energy and foraging requirements have suffered high rates of extinctions.     

A comparison of mixture toxicity assessment: examining the chronic toxicity of atrazine, permethrin and chlorothalonil in mixtures to Ceriodaphnia cf. dubia

Pesticides predominantly occur in aquatic ecosystems as mixtures of varying complexity, yet relatively few studies have examined the toxicity of pesticide mixtures. Atrazine, chlorothalonil and permethrin are widely used pesticides that have different modes of action. This study examined the chronic toxicities (7-d reproductive impairment) of these pesticides in binary and ternary mixtures to the freshwater cladoceran Ceriodaphnia cf. dubia. The toxicity of the mixtures was compared to that predicted by the independent action (IA) model for mixtures, as this is the most appropriate model for chemicals with different modes of action. Following this they were compared to the toxicity predicted by the concentration addition (CA) model for mixtures. According to the IA model, the toxicity of the chlorothalonil plus atrazine mixture conformed to antagonism, while that of chlorothalonil and permethrin conformed to synergism. The toxicity of the atrazine and permethrin mixture as well as the ternary mixture conformed to IA implying there was either no interaction between the components of these mixtures and/or in the case of the ternary mixture the interactions cancelled each other out to result in IA. The synergistic and antagonistic mixtures deviated from IA by factors greater than 3 and less than 2.5, respectively. When the toxicity of the mixtures was compared to the predictions of the CA model, the binary mixture of chlorothalonil plus atrazine, permethrin plus atrazine and the ternary mixture all conformed to antagonism, while the binary mixture of chlorothalonil plus permethrin conformed to CA. Using the CA model provided estimates of mixture toxicity that did not markedly underestimate the measured toxicity, unlike the IA model, and therefore the CA model is the most suitable to use in ecological risk assessments of these pesticides.     

Field demonstration of visible opacity photographic systems

The Digital Opacity Compliance System (DOCS) is an innovative method that uses digital imaging technology to quantify visible opacity of stationary sources. DOCS, which has been demonstrated at pilot and full scale as a technically defensible and economically attractive alternative to U.S. Environmental Protection Agency (EPA) Reference Method 9 (Method 9), uses commercial-off-the-shelf (COTS) digital cameras in combination with a user-friendly computer software package to determine opacity. To date, all DOCS field testing has been conducted using two models of digital cameras, notably, Kodak Models DC265 and DC290, both of which are no longer commercially available. To ensure that field-validated digital cameras will be available to future DOCS users, a suite of new digital cameras was evaluated with the opacity determination software including the following: (1) Sony Model Cybershot Model DSC-WI, (2) Nikon Model Coolpix 5200, (3) Fuji Finepix Model E500, and (4) Kodak Model DX6490. Within the opacity range of regulatory interest, that is, 0-40%, the Sony Cybershot Model DSC-WI and Nikon Coolpix Model 5200 digital cameras were found to generate plume photographs of which the DOCS opacity analysis yielded results that were statistically equivalent to the previously field-validated Kodak Model DC290. In contrast, the Fuji Finepix Model E500 generated plume photographs of which the DOCS opacity analysis were, on average, 2.2% less than those generated by the Kodak Model DC290 photographs, a difference that was determined to be statistically significant. Over the same opacity range, photographs taken by the Kodak Model DX6490 yielded DOCS opacity readings that were found to be statistically equivalent to a Method 9-certified transmissometer. Based on the results from the current digital camera validation testing approach, EPA has developed a new camera-based visible opacity measurement method titled "Determination of Visible Emission Opacity from Stationary Sources Using Computer-Based Photographic Analysis Systems." The proposed method is expected to be promulgated after closure of the public comment period.     

Contribution of the gasoline distribution cycle to volatile organic compound emissions in the metropolitan area of Mexico City

Gasoline distribution in the metropolitan area of Mexico City (MAMC) represents an area of opportunity for the abatement of volatile organic compound (VOC) emissions. The gasoline distribution in this huge urban center encompasses several operations: (1) storage in bulk and distribution plants, (2) transportation to gasoline service stations, (3) unloading at service stations' underground tanks, and (4) gasoline dispensing. In this study, hydrocarbon (HC) emissions resulting from breathing losses in closed reservoirs, leakage, and spillage from the operations just listed were calculated using both field measurements and reported emission factors. The results show that the contribution of volatile HC emissions due to storage, distribution, and sales of gasoline is 6651 t/year, approximately 13 times higher than previously reported values. Tank truck transportation results in 53.9% of the gasoline emissions, and 31.5% of emissions are generated when loading the tank trucks. The high concentration of emissions in the gasoline transportation and loading operations by tank trucks has been ascribed to (1) highly frequent trips from distribution plant to gasoline stations, and vice versa, to cope with excessive gasoline sales per gasoline station; (2) low leakproofness of tank trucks; and (3) poor training of employees. In addition, the contribution to HC evaporative and exhaust emissions from the vehicles of the MAMC was also evaluated.     

Development of an empirical model to estimate real-world fine particulate matter emission factors: the traffic air quality model

The purpose of the study was to quantify the impact of traffic conditions, such as free flow and congestion, on local air quality. The Borman Expressway (I-80/94) in Northwest Indiana is considered a test bed for this research because of the high volume of class 9 truck traffic traveling on it, as well as the existing and continuing installation of the Intelligent Transportation System (ITS) to improve traffic management along the highway stretch. An empirical traffic air quality (TAQ) model was developed to estimate the fine particulate matter (PM2.5) emission factors (grams per kilometer) based solely on the measured traffic parameters, namely, average speed, average acceleration, and class 9 truck density. The TAQ model has shown better predictions that matched the measured emission factor values more than the U.S. Environmental Protection Agency (EPA)-PART5 model. During congestion (defined as flow-speeds < 50 km/hr [30 mi/hr]), the TAQ model, on average, overpredicted the measured values only by a factor of 1.2, in comparison to a fourfold underprediction using the EPA-PART5 model. On the other hand, during free flow (defined as flow-speeds > 80 km/hr [50 mi/hr]), the TAQ model was conservative in that it overpredicted the measured values by 1.5-fold.     

Examining spatial patterns in polycyclic aromatic compounds measured in stream macroinvertebrates near a small subarctic oil and gas operation

The Cameron River runs through a small, remote petrochemical development in the Cameron Hills (Northwest Territories, Canada). In order to evaluate the exposure of aquatic biota to contaminants from oil and gas activities, we measured polycyclic aromatic compounds (PACs) in macroinvertebrates collected from sites and tributaries along the Cameron River, including upstream and downstream of the development, and sites located near drilled wells (developed). Macroinvertebrate tissue PAC burdens ranged from 0.2–2.8 μg g^?1 lipid for unsubstituted compounds, and from 4.2–63.2 μg g^?1 lipid for alkylated compounds, relatively low compared to similar studies from more industrialized regions in North America. There was no significant difference in tissue PAC burdens between upstream, downstream, or developed sites (p?=?0.12), although alkyl PACs in five out of seven developed sites were higher than the regional average. Petrogenic PACs were dominant in most samples, including alkyl fluorines, alkyl phenanthrene/anthracenes, and alkyl dibenzothiophenes. Minimal changes in PAC composition in macroinvertebrate tissues were detected along the Cameron River, with the exception of the two sites furthest downstream that had high concentrations of C3-C4 naphthalene. Overall, our results suggest that oil and gas development in the Cameron Hills has not resulted in substantial increases in PAC bioaccumulation in stream macroinvertebrates, although the potential that alkyl naphthalenes are being transported downstream from the development warrants further attention.     

Effects of Widespread Drought‐Induced Aspen Mortality on Understory Plants

Forest die‐off around the world is expected to increase in coming decades as temperature increases due to climate change. Forest die‐off will likely affect understory plant communities, which have substantial influence on regional biological diversity, ecosystem function, and land–atmosphere interactions, but how die‐off alters these plant communities is largely unknown. We examined changes in understory plant communities following a widespread, drought‐induced die‐off of trembling aspen (Populus tremuloides) in the western United States. We assessed shrub and herbaceous cover and volume in quadrats in 55 plots located across a wide range of levels of aspen mortality. We measured species richness and composition of herbaceous plant communities by recording species presence and absence in 12 sets of paired (1 healthy, 1 dying) aspen plots. Although understory composition in healthy and dying stands was heterogeneous across the landscape, shrub abundance, cover, and volume were higher and abundance of herbaceous species, cover, and volume were lower in dying aspen stands. Shrub cover and volume increased from 2009 to 2011 in dying stands, which suggests that shrub growth and expansion is ongoing. Species richness of herbs declined by 23% in dying stands. Composition of herbs differed significantly between dying and healthy stands. Richness of non‐native species did not differ between stand types. The understory community in dying aspen stands was not similar to other shrub‐dominated plant communities in the region and may constitute a novel community. Our results suggest that changes in understory plant communities as forests die off could be a significant indirect effect of climate change on biological diversity and forest communities. Efectos de la Mortalidad Extensiva de Álamos Inducida por Sequía sobre Plantas del Sotobosque     

Cryptic herbivores mediate the strength and form of ungulate impacts on a long-lived savanna tree

Plant populations are regulated by a diverse array of herbivores that impose demographic filters throughout their life cycle. Few studies, however, simultaneously quantify the impacts of multiple herbivore guilds on the lifetime performance or population growth rate of plants. In African savannas, large ungulates (such as elephants) are widely regarded as important drivers of woody plant population dynamics, while the potential impacts of smaller, more cryptic herbivores (such as rodents) have largely been ignored. We combined a large-scale ungulate exclusion experiment with a five-year manipulation of rodent densities to quantify the impacts of three herbivore guilds (wild ungulates, domestic cattle, and rodents) on all life stages of a widespread savanna tree. We utilized demographic modeling to reveal the overall role of each guild in regulating tree population dynamics, and to elucidate the importance of different demographic hurdles in driving population growth under contrasting consumer communities. We found that wild ungulates dramatically reduced population growth, shifting the population trajectory from increase to decline, but that the mechanisms driving these effects were strongly mediated by rodents. The impact of wild ungulates on population growth was predominantly driven by their negative effect on tree reproduction when rodents were excluded, and on adult tree survival when rodents were present. By limiting seedling survival, rodents also reduced population growth; however, this effect was strongly dampened where wild ungulates were present. We suggest that these complex interactions between disparate consumer guilds can have important consequences for the population demography of long-lived species, and that the effects of a single consumer group are often likely to vary dramatically depending on the larger community in which interactions are embedded.     

Identifying the possibilities and pitfalls of conducting IUCN Red List assessments from remotely sensed habitat information based on insights from poorly known Cuban mammals

The International Union for Conservation of Nature's Red List of Threatened Species (RLS) is the key global tool for objective, repeatable assessment of species’ extinction risk status, and plays an essential role in tracking biodiversity loss and guiding conservation action. Satellite remote sensing (SRS) data sets on global ecosystem distributions and functioning show exciting potential for informing range-based RLS assessment, but their incorporation has been restricted by low temporal resolution and coverage of data sets, lack of incorporation of degradation-driven habitat loss, and noninclusion of assumptions related to identification of changing habitat distributions for taxa with varying habitat dependency and ecologies. For poorly known mangrove-associated Cuban hutias (Mesocapromys spp.), we tested the impact of possible assumptions regarding these issues on range-based RLS assessment outcomes. Specifically, we used annual (1985–2018) Landsat data and land-cover classification and habitat degradation analyses across different internal time series slices to simulate range-based RLS assessments for our case study taxa to explore potential assessment uncertainty arising from temporal SRS data set coverage, incorporating proxies of (change in) habitat quality, and assumptions on spatial scaling of habitat extent for RLS parameter generation. We found extensive variation in simulated species-specific range-based RLS assessments, and this variation was mostly associated with the time series over which parameters were estimated. However, results of some species-specific assessments differed by up to 3 categories (near threatened to critically endangered) within the same time series, due to the effects of incorporating habitat quality and the spatial scaling used in RLS parameter estimation. Our results showed that a one-size-fits-all approach to incorporating SRS information in RLS assessment is inappropriate, and we urge caution in conducting range-based assessments with SRS for species for which habitat dependence on specific ecosystem types is incompletely understood. We propose novel revisions to parameter spatial scaling guidelines to improve integration of existing time series data on ecosystem change into the RLS assessment process.     

Identification of haemocytes and their role in clotting in the blue crab,Callinectes sapidus

Three types of haemocyte — hyaline cells, small granule and large granule haemocytes — have been identified in the circulation of blue crabs, Callinectes sapidus Rathbun, that were collected and processed in North Carolina, USA in February 1991. Differentiation of haemocytes begins in the haematopoietic tissue and continues in the circulation. Hyaline cells are distinguished morphologically by their relatively small size, high nucleocytoplasmic ratio and sparse cytoplasmic granule content. Small and large granule haemocytes are distinguished, respectively, by a preponderance of small and large electron dense granules in their cytoplasm. Furthermore, a light and electron microscopic examination of the clotting process performed in July 1991 revealed that hyaline cells initiated coagulation when exposed to seawater, whereas granular haemocytes did not undergo marked changes when so treated. These distinct functional and morphologic features suggest that the hyaline cell and granular haemocytes represent distinct cell lines. It remains unclear whether small granule haemocytes differentiate into large granule haemocytes.