Optimal background matching camouflage

Background matching is the most familiar and widespread camouflage strategy: avoiding detection by having a similar colour and pattern to the background. Optimizing background matching is straightforward in a homogeneous environment, or when the habitat has very distinct sub-types and there is divergent selection leading to polymorphism. However, most backgrounds have continuous variation in colour and texture, so what is the best solution? Not all samples of the background are likely to be equally inconspicuous, and laboratory experiments on birds and humans support this view. Theory suggests that the most probable background sample (in the statistical sense), at the size of the prey, would, on average, be the most cryptic. We present an analysis, based on realistic assumptions about low-level vision, that estimates the distribution of background colours and visual textures, and predicts the best camouflage. We present data from a field experiment that tests and supports our predictions, using artificial moth-like targets under bird predation. Additionally, we present analogous data for humans, under tightly controlled viewing conditions, searching for targets on a computer screen. These data show that, in the absence of predator learning, the best single camouflage pattern for heterogeneous backgrounds is the most probable sample.

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Inhibition or Facilitation? Contrasted Inter-Specific Interactions in Sphagnum under Laboratory and Field Conditions

Plants ◽

10.3390/plants9111554 ◽

2020 ◽

Vol 9 (11) ◽

pp. 1554

Author(s):

Chao Liu ◽

Zhao-Jun Bu ◽

Azim Mallik ◽

Yong-Da Chen ◽

Xue-Feng Hu ◽

...

Keyword(s):

Field Experiment ◽

Species Interactions ◽

Laboratory Experiments ◽

Resource Competition ◽

Specific Interactions ◽

Interaction Type ◽

Negative Effects ◽

Experiment Data ◽

The Stability ◽

Positive Effect

In a natural environment, plants usually interact with their neighbors predominantly through resource competition, allelopathy, and facilitation. The occurrence of the positive effect of allelopathy between peat mosses (Sphagnum L.) is rare, but it has been observed in a field experiment. It is unclear whether the stability of the water table level in peat induces positive vs. negative effects of allelopathy and how that is related to phenolic allelochemical production in Sphagnum. Based on field experiment data, we established a laboratory experiment with three neighborhood treatments to measure inter-specific interactions between Sphagnum angustifolium (Russ.) C. Jens and Sphagnum magellanicum Brid. We found that the two species were strongly suppressed by the allelopathic effects of each other. S. magellanicum allelopathically facilitated S. angustifolium in the field but inhibited it in the laboratory, and relative allelopathy intensity appeared to be positively related to the content of released phenolics. We conclude that the interaction type and intensity between plants are dependent on environmental conditions. The concentration of phenolics alone may not explain the type and relative intensity of allelopathy. Carefully designed combined field and laboratory experiments are necessary to reveal the mechanism of species interactions in natural communities.

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Effect of a dragonfly (<i>Bradinopyga strachani</i> Kirby, 1900) on the density of mosquito larvae in a field experiment using mesocosms

Web Ecology ◽

10.5194/we-18-81-2018 ◽

2018 ◽

Vol 18 (1) ◽

pp. 81-89 ◽

Cited By ~ 4

Author(s):

Daniel Acquah-Lamptey ◽

Roland Brandl

Keyword(s):

Field Experiment ◽

Laboratory Experiments ◽

Water Bodies ◽

Mosquito Population ◽

Mosquito Larvae ◽

Promising Strategy

Abstract. Laboratory experiments with food-deprived larvae of odonates suggested that these predators may have the potential to control mosquito populations. However, it remains unclear whether larvae of odonates co-occur with mosquito larvae in the field and whether larvae of odonates reduce the density of mosquito larvae in the field. We exposed 35 water-filled concrete containers in the field in shady and sunny conditions. Some of these containers were partially covered (for simplicity called closed containers, allowing only mosquitoes to lay eggs), whereas others remained open. The density of mosquito larvae was higher in shaded containers and in closed containers. The multivoltine odonate Bradinopyga strachani colonized open containers and the occurrence of these predators resulted in a clear reduction of the mosquito population. Our results indicate that increasing the colonization of water bodies by Bradinopyga strachani is a promising strategy for controlling populations of mosquitoes.

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LOW-LEVEL FEEDING OF TROLENE FOR CONTROL OF THE CATTLE GRUBS HYPODERMA LINEATUM (DE VILL.) AND H. BOVIS (L.)

Canadian Journal of Animal Science ◽

10.4141/cjas59-009 ◽

1959 ◽

Vol 39 (1) ◽

pp. 58-63 ◽

Cited By ~ 3

Author(s):

J. Weintraub ◽

C. O. M. Thompson ◽

M. C. Qually

Keyword(s):

Field Experiment ◽

Single Treatment ◽

Low Level ◽

Hypoderma Lineatum ◽

The Third ◽

Full Effect ◽

Cent Mortality

Calves were fed individually for 18 days on a ration of crushed oats treated with Trolene to give a daily dosage of 10 mg./kg. This treatment produced 94 per cent mortality of pre-hypodermal cattle grubs. This was not significantly different from 97 per cent mortality obtained with a single treatment by boluses at 100 mg./kg. The low-level treatment had no effect on the mortality of the pre-hypodermal grubs during the first week of treatment but reached its full effect before the beginning of the third week. Of the hypodermal grubs present at the time of treatment, 94 per cent died and the remainder pupated. The only symptom of toxicity observed was mild diarrhoea in the low-level-treated calves.In a field experiment, two groups of calves that had consumed treated range blocks daily at averages of 7.7 and 4.2 mg. Trolene/kg. for 93 and 64 days showed 95 and 88 per cent mortality, respectively, of the pre-hypodermal grubs. By comparison, another group of calves, treated with boluses at 110 mg. Trolene/kg., showed 80 per cent mortality. The average number of grubs surviving the three treatments were significantly different from each other and from the untreated controls (P <.01). All treatments were begun before hypodermal grubs had appeared. No symptoms of toxicity were seen in the calves of the two low-level-treated groups; ataxia of the hindquarters was observed in the bolus-treated calves on the day following treatment, but these symptoms disappeared on the same day without the use of an antidote.

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The chemical composition of the soil in a factorial experiment with citrus. I. Exchangeable metal cations and their effect on the cation content of citrus

Australian Journal of Agricultural Research ◽

10.1071/ar9600208 ◽

1960 ◽

Vol 11 (2) ◽

pp. 208 ◽

Cited By ~ 1

Author(s):

H Groenewegen ◽

D Bouma

Keyword(s):

Field Experiment ◽

Cover Crops ◽

Laboratory Experiments ◽

Appreciable Effect ◽

Exchangeable Calcium ◽

Cation Content ◽

Two Factors ◽

Exchangeable Magnesium ◽

Citrus Leaves ◽

Exchangeable Form

In a factorial field experiment with citrus it was found that application of ammonium sulphate caused a greater proportionate reduction in the exchangeable calcium of the soil than in the exchangeable potassium. Short-term laboratory experiments with virgin soil, to which ammonium was added, suggested that at least two factors were involved. If solutions of high electrolyte concentrations were added, a greater release of exchangeable calcium than of potassium occurred, relative to the amounts of these ions originally present in exchangeable form. Secondly, a release of potassium from non-exchangeable to exchangeable form also occurred. In the 0–4 in. layer of the field experiment, exchangeable magnesium was reduced in the same proportion as exchangeable calcium. In the 4–12 in. layer, exchangeable magnesium was reduced relatively more than calcium. The same trend was apparent in laboratory experiments. In one experiment, for example, the original amount of magnesium was reduced by 76 per cent., and calcium by 66 per cent. A comparison between cultural treatments showed that the potassium content of the soil from a bare surface treatment was much lower than that from treatments with cover crops. The changes in soil composition had no appreciable effect on the cation content of citrus leaves, and some reasons for this are discussed.

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Announcements of Support and Public Good Provision

The American Economic Review ◽

10.1257/aer.20130711 ◽

2017 ◽

Vol 107 (12) ◽

pp. 3760-3787 ◽

Cited By ~ 12

Author(s):

Judd B. Kessler

Keyword(s):

Public Goods ◽

Field Experiment ◽

Prosocial Behavior ◽

Public Good ◽

Large Scale ◽

Laboratory Experiments ◽

Public Good Provision ◽

Scale Field ◽

Large Scale Field ◽

Good Provision

Providing information about contributions to public goods is known to generate further contributions. However, it is often impossible to provide verifiable information on contributions. Through a large-scale field experiment and a series of laboratory experiments, I show that nonbinding announcements of support for a public good encourage others to contribute, even when actual contributions might not or cannot be made. Providing a way to easily announce support for a charity increases donations by $865 per workplace fundraising campaign (or 16 percent of average giving). I discuss implications for understanding prosocial behavior and for organizations aiming to increase contributions to public goods. (JEL C93, D64, D83, H41, L31)

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Nitrous oxide production from granular nitrogen fertilizers applied to a silt loam soil

Canadian Journal of Soil Science ◽

10.4141/s02-062 ◽

2003 ◽

Vol 83 (5) ◽

pp. 521-532 ◽

Cited By ~ 45

Author(s):

M. Tenuta and E. G. Beauchamp

Keyword(s):

Nitrous Oxide ◽

Field Experiment ◽

Laboratory Experiment ◽

Laboratory Experiments ◽

N Fertilizer ◽

Nitrogen Fertilizers ◽

Silt Loam ◽

N Fertilizers ◽

Oxide Production ◽

Nitrous Oxide Production

One field and two laboratory experiments were conducted to determine the relative magnitude and pattern of N2O production from several granular N fertilizers including urea, ammonium nitrate, calcium nitrate, ammonium sulfate and, in a laboratory experiment, monoammonium and diammonium phosphates. Several parameters, in particular soil water content, were studied for their roles in N2O production with these fertilizers. The field experiment was conducted at the Elora Research Station (20 km north of Guelph) on Conestoga silt loam during July on a site previously cropped to barley. Three methods were employed to assess N2O production following N fertilizer treatments in the field experiment, viz., soil cover, soil core and profile distribution. The data with each method revealed that incorporated urea produced the greatest quantity of N2O especially in the first few days following application. Shortly after urea application and incorporation (10 cm), N2O was detected at a depth of 50 cm indicating gas produced in the tilled layer was transported to lower depths. Data obtained with the intact core method showed that nitrification preceeded denitrification as the source of N2O produced during a wetting event as air-filled porosity decreased from 65% to less than 50%, respectively. The laboratory experiments showed that under aerobic conditions N2O production was generally greater with urea than the other N fertilizers. The greater production of N2O with urea was associated with N2O-accumulation. In the second laboratory experiment, saturating the soil following 14 d of aerobic incubation showed enhanced N2O production with ammonium phosphate fertilizers. Our findings indicate refinement of methods to predict N2O emissions based on N fertilizer source use and moisture can reduce uncertainties in national estimates of N2O emissions from agricultural soils. Key words: Nitrous oxide production, nitrogen fertilizers, soil atmosphere profiles, nitrification, denitrification, air-filled porosity

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Simulated Changes in Storm Morphology Associated with a Sea-Breeze Air Mass

Monthly Weather Review ◽

10.1175/mwr-d-20-0069.1 ◽

2020 ◽

Author(s):

Joshua Hartigan ◽

Robert A. Warren ◽

Joshua S. Soderholm ◽

Harald Richter

Keyword(s):

Front Propagation ◽

Sea Breeze ◽

Wind Fields ◽

Air Mass ◽

Convective Storms ◽

Low Level ◽

Environmental Air ◽

Homogeneous Environment ◽

Gust Front

AbstractThe central east coast of Australia is frequently impacted by large hail and damaging winds associated with severe convective storms, with individual events recording damages exceeding AU$1 billion. These storms present a significant challenge for forecasting due to their development in seemingly marginal environments. They often have been observed to intensify upon approaching the coast, with case studies and climatological analyses indicating that interactions with the sea breeze are key to this process. The relative importance of the additional lifting and vorticity along the sea-breeze front compared to the change to a cooler, moister air mass with stronger low-level shear behind the front has yet to be investigated. Here, the role of the sea-breeze air mass is isolated using idealized numerical simulations of storms developing in a horizontally homogeneous environment. The base-state substitution (BSS) modeling technique is utilized to introduce the sea-breeze air mass following initial storm development. Compared to a simulation without BSS, the storm is longer lived and more intense, ultimately developing supercell characteristics including increased updraft rotation, deviant motion to the left of the mean wind vector, and a strong reflectivity gradient on the inflow edge. Separately simulating the changes in the thermodynamic and wind fields reveals that the enhanced storm longevity and intensity are primarily due to the latter. The change in the low-level environmental winds slows gust front propagation, allowing the storm to continue to ingest warm, potentially buoyant environmental air. At the same time, increased low-level shear promotes the development of persistent updraft rotation causing the storm to transition from a multicell to a supercell.

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