The Glass is Half-Full: Overestimating the Quality of a Novel Environment is Advantageous

According to optimal foraging theory, foraging decisions are based on the forager's current estimate of the quality of its environment. However, in a novel environment, a forager does not possess information regarding the quality of the environment, and may make a decision based on a biased estimate. We show, using a simple simulation model, that when facing uncertainty in heterogeneous environments it is better to overestimate the quality of the environment (to be an “optimist”) than underestimate it, as optimistic animals learn the true value of the environment faster due to higher exploration rate. Moreover, we show that when the animal has the capacity to remember the location and quality of resource patches, having a positively biased estimate of the environment leads to higher fitness gains than having an unbiased estimate, due to the benefits of exploration. Our study demonstrates how a simple model of foraging with incomplete information, derived directly from optimal foraging theory, can produce well documented complex space-use patterns of exploring animals

Effects of Wind Turbine Noise on Songbird Behavior During Nonbreeding Season

Anthropogenic noise is one of the fastest growing, globally widespread pollutants, affecting countless species worldwide. Despite accumulating evidence of the negative impacts of wind turbines on wildlife, little is known about how the noise they generate affects ecological systems. Songbirds may be susceptible to noise pollution due to their reliance on vocal communication and thus, in this field study, we examined how songbirds are affected by wind turbine noise. We broadcasted noise produced by one wind turbine in a migratory stopover site during the nonbreeding season. Throughout the study, we repeatedly monitored the acoustic environment and songbird community before, during, and after the noise treatments with passive acoustic monitoring and mist netting. We employed generalized linear mixed effects models to assess the impact of experimental noise treatment on birds behavior and likelihood ratio tests to compare models with variables of interest with null models. The daily number of birds in the presence of wind turbine noise decreased by approximately 30% compared with the before and after phases. This reduction had a significant spatial pattern; the largest decrease was closer to the speaker and on its downwind side, fitting measured sound propagation. Although we found no impact on species diversity, two out of three most common species showed clear avoidance behavior: 45% and 36% decrease in abundance for the lesser whitethroat (Sylvia curruca) and Sardinian warbler (Sylvia melanocephala momus), respectively. In the after phase, there were lingering effects on the lesser whitethroat. The age structure of the lesser whitethroat population was affected because only juvenile birds showed avoidance behavior. No difference in avoidance extent was found between migratory and nonmigratory species, but the impacts of displacement on migrants during stopover are especially troubling from a conservation perspective. Our results stress the need to address the impacts of noise pollution on wildlife when planning noise-generating infrastructures, such as wind turbines, to allow for sustainable development without threatening already declining songbird populations

Look before you leap: is risk of injury a foraging cost?

Theory states that an optimal forager should exploit a patch so long as its harvest rate of resources from the patch exceeds its energetic, predation, and missed opportunity costs for foraging. However, for many foragers, predation is not the only source of danger they face while foraging. Foragers also face the risk of injuring themselves. To test whether risk of injury gives rise to a foraging cost, we offered red foxes pairs of depletable resource patches in which they experienced diminishing returns. The resource patches were identical in all respects, save for the risk of injury. In response, the foxes exploited the safe patches more intensively. They foraged for a longer time and also removed more food (i.e., had lower giving up densities) in the safe patches compared to the risky patches. Although they never sustained injury, video footage revealed that the foxes used greater care while foraging from the risky patches and removed food at a slower rate. Furthermore, an increase in their hunger state led foxes to allocate more time to foraging from the risky patches, thereby exposing themselves to higher risks. Our results suggest that foxes treat risk of injury as a foraging cost and use time allocation and daring—the willingness to risk injury—as tools for managing their risk of injury while foraging. This is the first study, to our knowledge, which explicitly tests and shows that risk of injury is indeed a foraging cost. While nearly all foragers may face an injury cost of foraging, we suggest that this cost will be largest and most important for predators

Dynamic Pathways for Viral Capsid Assembly

We develop a class of models with which we simulate the assembly of particles into T1 capsid-like objects using Newtonian dynamics. By simulating assembly for many different values of system parameters, we vary the forces that drive assembly. For some ranges of parameters, assembly is facile, while for others, assembly is dynamically frustrated by kinetic traps corresponding to malformed or incompletely formed capsids. Our simulations sample many independent trajectories at various capsomer concentrations, allowing for statistically meaningful conclusions. Depending on subunit (i.e., capsomer) geometries, successful assembly proceeds by several mechanisms involving binding of intermediates of various sizes. We discuss the relationship between these mechanisms and experimental evaluations of capsid assembly processes.Comment: 13 pages, 13 figures. Submitted to Biophys.

What evidence exists on the effects of anthropogenic noise on acoustic communication in animals? A systematic map protocol

Background: Noise pollution is an intense, widespread anthropogenic disturbance that can have highly detrimental impacts on natural populations, communities, and ecosystems across the globe. One major way through which noise can affect wildlife is by masking acoustic signals that animals rely on and, in doing so, hindering inter- and intraspecific communication among individuals. In response, many animals change their vocal behavior in an attempt to overcome the signal- and cue-masking effects of noisy environments. This can be done by changing the amplitude of the vocal output, shifting its frequency, or changing its temporal structure. However, to date, we still know very little about the ecological contexts of signal modifications in animals or their fitness consequences. We present a protocol for a systematic map aiming to collect and characterize all research done on animals' signal modification in response to anthropogenic noise. The map will increase our understanding of the consequences of noise pollution on animal communication and may guide the development of new mitigation tools to alleviate any negative effects. The map will also allow us to identify gaps in the literature and highlight possible future research areas. Methods: We will collect information about different types of acoustic modifications in response to noise as well as information about the noise's source and properties. The map will also include the ecological context of the signal modification and the fitness consequences of the modification, if measured. We will search both commercially published literature and grey literature, and conduct the searches in academic journal databases, online search engines, and specialist websites. Articles will be screened for inclusion at title, abstract and full-text levels and will then be critically appraised for study robustness and validity. Data will then be extracted and coded according to categories informed by consultation with stakeholders. Data will be summarized in a quantitative manner, accompanied with a narrative review that will map our knowledge on how animals change their vocalizations in response to noise pollution as a function of their taxa, geographic location, noise pollution source, and vocalization type.Peer reviewe

Clinical Features and Outcomes of Paediatric Patients With Isolated Colonic Crohn Disease

Objectives: Adult studies suggest that patients with isolated colonic Crohn disease (L2 CD) exhibit unique characteristics differentiating them from patients with ileo-caecal (L1) CD and ulcerative colitis (UC). We aimed to characterize clinical features and outcomes of paediatric patients with L2. Methods: Retrospective data was collected through the Porto Inflammatory Bowel Disease group of the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) on Paediatric patients with L2, L1 or UC at different time-points. Outcome measures included time to first flare, hospital admissions, initiation of anti-tumor necrosis factor-alpha (TNF alpha) drug, stricture and surgery. Results: Three hundred patients were included: 102 L1, 94 L2 and 104 UC. Rates of hematochezia at presentation were 14.7%, 44.7% and 95.2%, while rates of fever were 12.7%, 26.6% and 2.9%, for patients with L1, L2 and UC, respectively (P < 0.001 for all comparisons). Skip lesions were identified in 65% of patients with L2, and granulomas in 36%, similar to L1 patients. Rates of anti-Saccharomyces cerevisiae antibodies (ASCA) and perinuclear antineutrophil cytoplasmic (pANCA) positivity significantly differed between the three groups: 25.4% and 16.7% for patients with L2, compared with 55.2% and 2.3%, and 1.8% and 52.9% for patients with L1 and UC, respectively. Response rates to exclusive enteral nutrition were comparable between L1 and L2 (78.3-82.4%), as was the response to oral steroids (70.4-76.5%) in the three groups. While times to first flare and admission were similar between groups, patients with L1 were commenced on anti-TNF alpha earlier. Moreover, stricturing phenotype and need for colectomy were very rare in patients with L2. Conclusions: Significant differences are observed in the clinical presentation and outcomes of Paediatric patients with L2, compared to patients with L1 and UC.Peer reviewe

Staying warm or moist? Operative temperature and thermal preferences of common frogs (Rana temporaria), and effects on locomotion

Ambient temperature largely determines the body temperature of amphibians, and thus their hydration state and physiological performance. Microhabitat conditions chosen by terrestrial amphibians may represent a trade-off between high ambient temperatures, which maximize performance but cause high rates of water loss, and low temperatures, which, in turn, slow desiccation, but potentially hinder performance. We determined the operative temperature of common frogs (Rana temporaria) by placing 3% agar models in different microhabitats and measuring their temperature and water loss. Temperature measurements derived from the models accurately matched the body temperature of live frogs placed in the same microhabitat. Operative temperatures were lower than ambient temperatures on a warm day, probably because of evaporative water loss, but they were similar to or even slightly higher than ambient temperatures on a cool day, possibly because of warmth from the substrate. Frogs in the field selected moist and cool habitats, and their body temperatures ranged from 15 to 21 °C. In a temperature gradient in the laboratory, captive frogs chose significantly higher temperatures (19.4±1.7 °C) when the gradient floor was covered entirely with wet sand than when sand was wet in the cool end, but dry in the warm end (17.6±2.5 °C). The relevance of the preferred temperature was assessed through jumping performance experiments, using frogs with different body temperatures. Jump length was lower at low body temperature (6 °C) than at higher body temperatures, and peaked at 15 °C. Our results suggest that the frogs select favourable microhabitats of intermediate temperature, which could result in reduced water loss and peak physiological and behavioural performance.Prof. Sue W. Nicolson and the National Research Foundation, South Africa, are thanked for funding A.K.’s journey to Poland. C.R.T. was supported by a grant from the Australian Research Council (DP0879851).http://www.thebhs.org/pubs_journal.htmlab201