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Cheng-Shiuan Lee, Nicholas S Fisher
Methylmercury (MeHg) is known to biomagnify in marine food chains, resulting in higher concentrations in upper trophic level animals than their prey. To better understand how marine copepods, an important intermediate between phytoplankton and forage fish at the bottom of the food chain, assimilate and release MeHg, we performed a series of laboratory experiments using the gamma-emitting radiotracer (203) Hg(2+) and Me(203) Hg with the calanoid copepod Acartia tonsa. Assimilation efficiencies (AEs) of Hg(2+) and MeHg ranged from 25 to 31% and 58 to 79%, respectively, depending on algal diets...
October 20, 2016: Environmental Toxicology and Chemistry
Zachary Y Huang, Stephanie Lin, Kiheung Ahn
Methoprene, a juvenile hormone (JH) analog, is a widely used insecticide that also accelerates behavioral development in honey bees (Apis mellifera). JH regulates the transition from nursing to foraging in adult worker bees, and treatment with JH or methoprene have both been shown to induce precocious foraging. To determine how methoprene changes honey bee behavior, we compared JH titers of methoprene-treated and untreated bees. Behavioral observations confirmed that methoprene treatment significantly increased the number of precocious foragers in 3 out of 4 colonies...
October 20, 2016: Insect Science
Christine L Madliger, Oliver P Love
The application of physiological measures to conservation monitoring has been gaining momentum and, while a suite of physiological traits are available to ascertain disturbance and condition in wildlife populations, glucocorticoids (i.e., GCs; cortisol and corticosterone) are the most heavily employed. The interpretation of GC levels as sensitive indicators of population change necessitates that GCs and metrics of population persistence are linked. However, the relationship between GCs and fitness may be highly context-dependent, changing direction, or significance, depending on the GC measure, fitness metric, life history stage, or other intrinsic and extrinsic contexts considered...
July 27, 2016: Ecological Applications: a Publication of the Ecological Society of America
L Chen, G Guo, X J Yuan, J Zhang, A Y Wen, X H Sun, T Shao
The objective of this study was to determine the effect of ensiling different ratios of whole crop oat to lucerne on fermentation quality, aerobic stability and in vitro digestibility of silage on the Tibetan plateau. Four experimental treatments were produced varying in the ratio of forages on a fresh matter (FM) basis: 1) 100% oat (control, dry matter (DM) content: 317 g/kg), 2) 90% oat + 10% lucerne (OL10, DM content: 316 g/kg), 3) 80% oat+ 20% lucerne (OL20, DM content: 317 g/kg) and 4) 70% oat+ 30% lucerne (OL30, DM content: 318 g/kg)...
October 20, 2016: Journal of Animal Physiology and Animal Nutrition
April Hayward, Mariela Pajuelo, Catherine G Haase, David M Anderson, James F Gillooly
Dive duration in air-breathing vertebrates is thought to be constrained by the volume of oxygen stored in the body and the rate at which it is consumed (i.e., "oxygen store/usage hypothesis"). The body mass-dependence of dive duration among endothermic vertebrates is largely supportive of this model, but previous analyses of ectothermic vertebrates show no such body mass-dependence. Here we show that dive duration in both endotherms and ectotherms largely support the oxygen store/usage hypothesis after accounting for the well-established effects of temperature on oxygen consumption rates...
2016: PeerJ
Pedro H C Pereira, Marcus Santos, Daniel L Lippi, Pedro Silva
Parrotfish are fundamental species in controlling algal phase-shifts and ensuring the resilience of coral reefs. Nevertheless, little is known on their ecological role in the south-western Atlantic Ocean. The present study analysed the ontogenetic foraging activity and feeding selectivity of the Brazilian endemic parrotfish Scarus zelindae using behavioural observation and benthic composition analyses. We found a significant negative relationship between fish size and feeding rates for S. zelindae individuals...
2016: PeerJ
Masakazu Asahara, Masahiro Koizumi, Thomas E Macrini, Suzanne J Hand, Michael Archer
The modern platypus, Ornithorhynchus anatinus, has an eye structure similar to aquatic mammals; however, platypuses also have a "sixth sense" associated with the bill electro- and mechanoreception that they use without opening their eyes underwater. We hypothesize that Ornithorhynchus and the Miocene taxon Obdurodon have different sensory capacities, which may have resulted from differences in foraging behavior. To estimate differences in foraging, sensory systems, and anatomical divergence between these monotremes, we compared their skull morphologies...
October 2016: Science Advances
Christine L Madliger, Oliver P Love
Labile physiological variables, such as stress hormones [i.e. glucocorticoids (GCs)], allow individuals to react to perturbations in their environment and may therefore reflect the effect of disturbances or positive conservation initiatives in advance of population-level demographic measures. Although the application of GCs as conservation biomarkers has been of extensive interest, few studies have explicitly investigated whether baseline GC concentrations respond to disturbances consistently across individuals...
2016: Conservation Physiology
Linda J Gormezano, Scott R McWilliams, David T Iles, Robert F Rockwell
Trade-offs between locomotory costs and foraging gains are key elements in determining constraints on predator-prey interactions. One intriguing example involves polar bears pursuing snow geese on land. As climate change forces polar bears to spend more time ashore, they may need to expend more energy to obtain land-based food. Given that polar bears are inefficient at terrestrial locomotion, any extra energy expended to pursue prey could negatively impact survival. However, polar bears have been regularly observed engaging in long pursuits of geese and other land animals, and the energetic worth of such behaviour has been repeatedly questioned...
2016: Conservation Physiology
Michael A Mole, Shaun Rodrigues DÁraujo, Rudi J van Aarde, Duncan Mitchell, Andrea Fuller
Most of southern Africa's elephants inhabit environments where environmental temperatures exceed body temperature, but we do not know how elephants respond to such environments. We evaluated the relationships between apparent thermoregulatory behaviour and environmental, skin and core temperatures for tame savanna elephants (Loxodonta africana) that were free-ranging in the hot parts of the day, in their natural environment. Environmental temperature dictated elephant behaviour within a day, with potential consequences for fine-scale habitat selection, space use and foraging...
2016: Conservation Physiology
Simone Vincenzi, Alain J Crivelli, Stephan Munch, Hans J Skaug, Marc Mangel
Better understanding of variation in growth will always be an important problem in ecology. Individual variation in growth can arise from a variety of processes; for example, individuals within a population vary in their intrinsic metabolic rates and behavioral traits, which may influence their foraging dynamics and access to resources. However, when adopting a growth model, we face trade-offs between model complexity, biological interpretability of parameters, and goodness of fit. We explore how different formulations of the von Bertalanffy growth function (vBGF) with individual random effects and environmental predictors affect these trade-offs...
July 2016: Ecological Applications: a Publication of the Ecological Society of America
Hannah B Vander Zanden, Alan B Bolten, Anton D Tucker, Kristen M Hart, Margaret M Lamont, Ikuko Fujisaki, Kimberly J Reich, David S Addison, Katherine L Mansfield, Katrina F Phillips, Mariela Pajuelo, Karen A Bjorndal
Assessments of large-scale disasters, such as the Deepwater Horizon oil spill, are problematic because while measurements of post-disturbance conditions are common, measurements of pre-disturbance baselines are only rarely available. Without adequate observations of pre-disaster organismal and environmental conditions, it is impossible to assess the impact of such catastrophes on animal populations and ecological communities. Here, we use long-term biological tissue records to provide pre-disaster data for a vulnerable marine organism...
October 2016: Ecological Applications: a Publication of the Ecological Society of America
Kelly M Proffitt, Mark Hebblewhite, Wibke Peters, Nicole Hupp, Julee Shamhart
Understanding how habitat and nutritional condition affect ungulate populations is necessary for informing management, particularly in areas experiencing carnivore recovery and declining ungulate population trends. Variations in forage species availability, plant phenological stage, and the abundance of forage make it challenging to understand landscape-level effects of nutrition on ungulates. We developed an integrated spatial modeling approach to estimate landscape-level elk (Cervus elaphus) nutritional resources in two adjacent study areas that differed in coarse measures of habitat quality and related the consequences of differences in nutritional resources to elk body condition and pregnancy rates...
October 2016: Ecological Applications: a Publication of the Ecological Society of America
Nadja Danner, Anna Maria Molitor, Susanne Schiele, Stephan Härtel, Ingolf Steffan-Dewenter
Honey bees (Apis mellifera L.) show a large variation in foraging distances and use a broad range of plant species as pollen resources, even in regions with intensive agriculture. However, it is unknown how increasing areas of mass-flowering crops like oilseed rape (Brassica napus; OSR) or a decrease of seminatural habitats (SNH) change the temporal and spatial availability of pollen resources for honey bee colonies, and thus foraging distances and frequency in different habitat types. We studied pollen foraging of honey bee colonies in 16 agricultural landscapes with independent gradients of OSR and SNH area within 2 km and used waggle dances and digital geographic maps with major land cover types to reveal the distance and visited habitat type on a landscape level...
September 2016: Ecological Applications: a Publication of the Ecological Society of America
XianJun Yuan, AiYou Wen, Seare T Desta, ZhiHao Dong, Tao Shao
BACKGROUND: Short-chain fatty salts have been widely used as food and forage preservatives because of their antimicrobial properties. This study evaluated the effects of 4 chemical compounds with antimicrobial property on nitrogen transformations and intrinsic protease activity of alfalfa silage. RESULTS: Potassium diformate and formic acid rapidly reduced silage pH. Silages treated with sodium diacetate (SD) and calcium propionate (CAP) had higher final peptide N concentrations than other silage...
October 18, 2016: Journal of the Science of Food and Agriculture
Jan-Dieter Ludwigs, Markus Ebeling, Timothy B Fredricks, Roger C Murfitt, Steven Kragten
The registration of pesticides follows guidance published by the European Food Safety Authority, EFSA. As a default, the EFSA guidance document on risk assessment for birds and mammals assumes that animals feed exclusively on pesticide-treated fields. However, the guidance document suggests refining the risk via the proportion of food animals obtain from a treated field or specific crop (expressed via the so-called PT value). The EFSA guidance equalizes the portion of food taken from a treated area per day with the portion of time spent potentially foraging over the course of a day within this area...
October 18, 2016: Environmental Toxicology and Chemistry
Fikeremaryam Birara Feleke, Melaku Berhe, Getachew Gebru, Dana Hoag
The livestock sector serves as a foremost source of revenue for rural people, particularly in many developing countries. Among the livestock species, sheep and goats are the main source of livelihood for rural people in Ethiopia; they can quickly multiply, resilient and are easily convertible to cash to meet financial needs of the rural producers. The multiple contributions of sheep and goat and other livestock to rural farmers are however being challenged by climate change and variability. Farmers are responding to the impacts of climate change by adopting different mechanisms, where choices are largely dependent on many factors...
2016: SpringerPlus
Bernardo Duarte, Maria Teresa Cabrita, Carla Gameiro, Ana Rita Matos, Rita Godinho, João Carlos Marques, Isabel Caçador
A profound analysis of A. tripolium photochemical traits under salinity exposure is lacking in the literature, with very few references focusing on its fatty acid profile role in photophysiology. To address this, the deep photochemical processes were evaluated by Pulse Amplitude Modulated (PAM) Fluorometry coupled with a discrimination of its leaf fatty acid profile. Plants exposed to 125-250 mM NaCl showed higher photochemical light harvesting efficiencies and lower energy dissipation rates. under higher NaCl exposure, there is evident damage of the oxygen evolving complexes (OECs)...
October 17, 2016: Plant Biology
Stefan Abrahamczyk, Michael Kessler, Daniel Hanley, Dirk N Karger, Matthias P J Müller, Anina C Knauer, Felix Keller, Michael Schwerdtfeger, Aelys M Humphreys
A longstanding debate concerns whether nectar sugar composition evolves as an adaptation to pollinator dietary requirements or whether it is 'phylogenetically constrained'. Here we use a modeling approach to evaluate the hypothesis that nectar sucrose proportion (NSP) is an adaptation to pollinators. We analyze ~2,100 species of asterids, spanning several plant families and pollinator groups (PGs), and show that the hypothesis of adaptation cannot be rejected: NSP evolves toward two optimal values, high NSP for specialist-pollinated and low NSP for generalist-pollinated plants...
October 16, 2016: Journal of Evolutionary Biology
Teemu Aitta-Aho, Elpiniki Pappa, Denis Burdakov, John Apergis-Schoute
The hypothalamic hypocretin/orexin (HO) system holds a central role in the regulation of several physiological functions critical for food-seeking behavior including mnemonic processes for effective foraging behavior. It is unclear however whether physiological increases in HO neuronal activity can support such processes. Using a designer rM3Ds receptor activation approach increasing HO neuronal activity resulted in improved short-term memory for novel locations. When tested on a non-spatial novelty object recognition task no significant difference was detected between groups indicating that hypothalamic HO neuronal activation can selectively facilitate short-term spatial memory for potentially supporting memory for locations during active exploration...
October 13, 2016: Neurobiology of Learning and Memory
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