Effects of Background Color and Predation Risk on Color Change in Fire Salamander Larvae

2009 ◽  
Vol 55 (4) ◽  
pp. 359-367 ◽  
Author(s):  
Ori Segev
Keyword(s):  
Predation Risk ◽  
Perceived Risk ◽  
Color Change ◽  
White Background ◽  
Color Matching ◽  
Background Color ◽  
Background Matching ◽  
Threat Sensitivity ◽  
Risk Of Predation ◽  
Fire Salamander

The threat-sensitivity hypothesis assumes individuals should demonstrate flexibility in response to perceived predation risk and vary the intensity of anti-predator responses in concert with perceived risk of predation. Substrate color matching is adaptive as it enables organisms to become less conspicuous to both their prey and predators. I hypothesized that newborn fire salamander (Salamandra infraimmaculata) larvae will respond fast through physiological color change to contrasting backgrounds, becoming lighter against a white background and darker against a black background. Additionally, in accordance with the threat-sensitivity hypothesis, I expected a background color x predator interaction—i.e., that predator presence will further enhance the focal larvae color-matching response. To explicitly test these hypotheses I conducted a replicated outdoor mesocosm experiment. I used a two-by-two factorial design: pools of black or white background color crossed with the presence or absence of a larger cannibalistic conspecific. Digital photos of the focal larvae's dorsal view revealed that larval brightness and chroma changed accordingly against the contrasting black and white backgrounds to increase background matching. Although not statistically significant, larvae tended to show a stronger color-change response towards enhanced background matching in the presence of the free predator. Larval survival was strongly reduced in the presence of the larger conspecific, with no apparent effect of background color. This study demonstrates that Salamandra larvae are capable of environmentally induced physiological color change and highlights the need for further investigation into the interplay between threat intensity, mechanisms of risk assessment, and physiological antipredator responses.

Developmental costs of yellow colouration in fire salamanders and experiments to test the efficiency of yellow as a warning colouration

2020 ◽  
Vol 41 (3) ◽  
pp. 373-385 ◽  
Author(s):  
Barbara A. Caspers ◽  
E. Tobias Krause ◽  
Isabelle Hermanski ◽  
Christopher Wiesbrock ◽  
Friedrich-Wilhelm Kastrup ◽  
...  
Keyword(s):  
Predation Risk ◽  
Carabid Beetles ◽  
Colour Pattern ◽  
Natural Habitats ◽  
Yellow Colour ◽  
Risk Of Predation ◽  
Fire Salamander ◽  
Food Conditions ◽  
In Fire ◽  
Salamander Larvae

Abstract Warning colouration reduces predation risk by signalling or mimicking the unpleasantness of prey and therefore increases survival. We tested in two experiments the evolutionary costs and benefits of the yellow colour pattern in fire salamanders (Salamandra salamandra), which display a yellow/black colour pattern usually associated with toxic alkaloids. Our first experiment aimed to test whether the development of colouration is condition dependent and thus related to developmental costs, i.e. influenced by resource availability during the developmental process. Therefore, we reared fire salamander larvae under different nutritional conditions and compared the relative amount of yellow they developed after metamorphosis. Fire salamander larvae reared under limited food conditions had a lower proportion of yellow following metamorphosis than control larvae reared under superior food conditions. In a second experiment we tested whether the proportion of yellow has an impact on the risk of being attacked using artificial models. We tested, in salamander-free and salamander-occupied natural habitats, whether artificial clay models with different proportions of yellow and black receive different attack rates from potential predators (birds, mammals, insects). In clay models the proportion of yellow and the site had a significant effect on predation risk. Models with larger amounts of yellow had fewer bite marks from predators such as carabid beetles and birds, but only in sympatry with salamanders. In conclusion, the early expression of conspicuous colouration seems to be condition dependent and therefore potentially costly. Furthermore, the yellow colouration of fire salamanders act as a signal that potentially reduces their risk of being attacked by predators. Thus, the yellow colouration of fire salamanders seems to represent an adaptive trait that reduces the risk of predation, which can be expressed in higher quantity by individuals of a certain condition.

The control of color change in the Pacific tree frog, Hyla regilla

2004 ◽  
Vol 82 (6) ◽  
pp. 889-896 ◽  
Author(s):  
James C Stegen ◽  
C M Gienger ◽  
Lixing Sun
Keyword(s):  
Light Intensity ◽  
Environmental Variables ◽  
Color Change ◽  
Interactive Effects ◽  
Tree Frog ◽  
Background Color ◽  
Hyla Regilla ◽  
Background Matching ◽  
The Pacific ◽  
Initial Color

A number of environmental variables have been identified as affecting anuran color, but rarely have the interactions between these variables been investigated. In attempt to elucidate the function of color change, we conducted a within-subject, full factorial experiment designed to determine the simple and interactive effects of background, temperature, and light intensity on the rate of color change in the Pacific tree frog (Hyla regilla Baird and Girard, 1852). Color was investigated holistically, as well as by decomposing it into its constituent parts (hue, chroma, and lightness), using digital photography. The rate of color change was faster on the green versus the brown background, at 10 versus 25 °C, and at low versus high light intensity. There was also a significant effect of the interaction between background color and temperature on the rate of color change. We found increased rates of hue, chroma, lightness, and color change with increasing initial hue, chroma, lightness, and color distances between the Pacific tree frog and its background, respectively. In addition, initial color distance covaried with changes in environmental variables. After controlling for initial color distance, and thus the effects of background matching, background color and temperature still showed a significant interaction for their effects on rate of color change. These results suggest that crypsis (i.e., background matching) is not the only function of physiological color change in H. regilla. Physiological color change may also be used to hydro- and (or) thermo-regulate.

scholarly journals The strength of a female mate preference increases with predation risk

2008 ◽  
Vol 276 (1657) ◽  
pp. 775-780 ◽  
Author(s):  
Tae Won Kim ◽  
John H Christy ◽  
Stefan Dennenmoser ◽  
Jae C Choe
Keyword(s):  
Sexual Selection ◽  
Predation Risk ◽  
Perceived Risk ◽  
General Pattern ◽  
Visual Orientation ◽  
Relative Preference ◽  
Avian Predators ◽  
Risk Of Predation ◽  
Courtship Signals ◽  
Perceived Predation Risk

When females search for mates and their perceived risk of predation increases, they less often express preferences for males that use conspicuous courtship signals, relaxing sexual selection on production of these signals. Here, we report an apparent exception to this general pattern. Courting male fiddler crabs Uca beebei sometimes build pillars of mud at the openings to their burrows in which crabs mate. Females visit several males before they choose a mate by staying and breeding in their burrows, and they preferentially visit males with pillars. Previous studies suggested that this preference is based on a visual orientation behaviour that may reduce females' risk of predation while searching for a mate. We tested this idea by determining whether the female preference for males with pillars increases with perceived predation risk. We attracted avian predators to where crabs were courting and measured the rates that sexually receptive females visited courting males with and without mud pillars. Under elevated risk, females continued to search for mates and they showed a stronger relative preference for males with pillars. Thus, when predation risk is high, females may continue to express preferences that are under natural selection because they help females avoid predation, strengthening sexual selection for use of the preferred signal.

Do long-tailed macaques avoid large heterospecific carcasses?

Behaviour ◽  
2021 ◽  
pp. 1-12
Author(s):  
Jeffrey V. Peterson ◽  
Agustín Fuentes
Keyword(s):  
Predation Risk ◽  
Nonhuman Primate ◽  
Perceived Risk ◽  
Macaca Fascicularis ◽  
Future Research ◽  
Tree Line ◽  
Risk Of Predation ◽  
Vigilance Behaviour ◽  
Pathogen Avoidance

Abstract This anecdotal observation details the response of long-tailed macaques (Macaca fascicularis) to a heterospecific carcass. The subgroup of macaques we were following abruptly changed their direction of travel upon reaching a tree line while displaying silent vigilance behaviour. We later discovered a dog carcass in the area and concluded their behaviour may have been in response to the smell of that carcass. The carcass was not visible from the response point at the tree line due to its distance from that point (approximately 30 meters) and the uneven and densely vegetated terrain between. The macaques were therefore most likely responding to scent cues from the carcass. We suggest the observed vigilance behaviour is excessive under a strictly pathogen-avoidance explanation and may be understood as a response to a cue of potential predation risk. We review alternative explanations and suggest future research on nonhuman primate heterospecific carcass avoidance is necessary to fully assess the potential relation to perceived risk of predation.

scholarly journals Plasticity of parental care under the risk of predation: how much should parents reduce care?

2013 ◽  
Vol 9 (4) ◽  
pp. 20130154 ◽  
Author(s):  
Cameron K. Ghalambor ◽  
Susana I. Peluc ◽  
Thomas E. Martin
Keyword(s):  
Parental Care ◽  
Predation Risk ◽  
Perceived Risk ◽  
Nest Predation ◽  
Behavioural Plasticity ◽  
Risk Of Predation ◽  
Theoretical Predictions ◽  
The Mean ◽  
Parental Provisioning ◽  
Nest Predator

Predation can be an important agent of natural selection shaping parental care behaviours, and can also favour behavioural plasticity. Parent birds often decrease the rate that they visit the nest to provision offspring when perceived risk is high. Yet, the plasticity of such responses may differ among species as a function of either their relative risk of predation, or the mean rate of provisioning. Here, we report parental provisioning responses to experimental increases in the perceived risk of predation. We tested responses of 10 species of bird in north temperate Arizona and subtropical Argentina that differed in their ambient risk of predation. All species decreased provisioning rates in response to the nest predator but not to a control. However, provisioning rates decreased more in species that had greater ambient risk of predation on natural nests. These results support theoretical predictions that the extent of plasticity of a trait that is sensitive to nest predation risk should vary among species in accordance with predation risk.

Evaluation of Color-matching Ability of a Structural Colored Resin Composite

2021 ◽  
Author(s):  
M Saegusa ◽  
H Kurokawa ◽  
N Takahashi ◽  
T Takamizawa ◽  
R Ishii ◽  
...  
Keyword(s):  
Resin Composite ◽  
Color Measurement ◽  
White Background ◽  
Color Matching ◽  
Background Color ◽  
Cavity Depth ◽  
B Values ◽  
Black Background ◽  
Artificial Teeth ◽  
Excellent Color

Clinical Relevance Although excellent color-matching ability was confirmed for the structural colored resin composite Omnichroma, care should be taken to ensure that the appropriate chromatic color conditions for restoration are achieved in the oral environment. SUMMARY Purpose: The present study evaluated the color-matching ability of a structural colored resin composite to compare it with resin composites employing pigments. Methods and Materials: A structural colored resin composite (Omnichroma [OMC]), a supranano-filled resin composite (Estelite Σ Quick [ELQ]), and a nano-filled resin composite (Filtek Supreme Ultra [FSU]) were used. Each resin composite was packed into a Teflon mold and pressed down with a clear strip under a glass slide. The specimens were light irradiated through the slide with a light-emitting diode curing unit. The thickness of the specimens (n=6) was measured with a digital caliper before being transferred to distilled water and stored at 37°C for 24 hours. The measurements of the optical characteristics of the specimens on a black-and-white background were performed using a spectrophotometer. D65 (CIE D65) was used as a light source for the spectrophotometer. Measurements were repeated three times for each specimen under each color-measurement condition, and average values for three same-shade specimens were calculated. One-way analysis of variance and Tukey post hoc tests were used (α=0.05). To determine its ability to match the color of artificial teeth, each shade of resin composite was placed in a cavity before performing color measurements. Using a spectrophotometer (CMS-35F S/C) with a flexible sensor, L*, a*, and b* values were obtained. Results: The spectral reflectance curve of OMC showed that it reflected light wavelengths from 430-700 nm regardless of the background color and thickness of the specimens. The percentage of reflectance of ELQ decreased near wavelengths of 550-580 nm. Regarding the influence of background color on CIE L*, a*, b* values, the L* level showed significantly higher values for all tested materials with white backgrounds, and OMC was most affected by the difference in background color. However, a* values of ELQ and FSU were significantly higher with a black background than with a white background, and OMC showed a significantly higher value with a white background than with a black background. The b* values were higher with a white background than with a black background and were significantly higher for all three products, and these tendencies were much greater for ELQ and FSU. Conclusions: The ability of OMC to match the color of artificial teeth showed acceptable color compatibility, regardless of the shade of the artificial teeth and the depth of the cavity. However, ELQ and FSU showed reduced color compatibility, especially for a cavity depth of 3.0 mm. Excellent color matching ability was confirmed for the structural colored resin composite OMC, resulting in reduced color differences and therefore improving the esthetic appearance of the restoration, simplifying shade matching, and compensating for any color mismatch.

Elevated nest predation risk promotes offspring size variation in birds with prolonged parental care.

2019 ◽  
Author(s):  
Gretchen F. Wagner ◽  
Emeline Mourocq ◽  
Michael Griesser
Keyword(s):  
Predation Risk ◽  
Reproductive Cycle ◽  
Perceived Risk ◽  
Nest Predation ◽  
Bird Species ◽  
Size Variation ◽  
Egg Laying ◽  
Offspring Size ◽  
Natural Predation ◽  
Risk Spreading

Predation of offspring is the main cause of reproductive failure in many species, and the mere fear of offspring predation shapes reproductive strategies. Yet, natural predation risk is ubiquitously variable and can be unpredictable. Consequently, the perceived prospect of predation early in a reproductive cycle may not reflect the actual risk to ensuing offspring. An increased variance in investment across offspring has been linked to breeding in unpredictable environments in several taxa, but has so far been overlooked as a maternal response to temporal variation in predation risk. Here, we experimentally increased the perceived risk of nest predation prior to egg-laying in seven bird species. Species with prolonged parent-offspring associations increased their intra-brood variation in egg, and subsequently offspring, size. High risk to offspring early in a reproductive cycle can favour a risk-spreading strategy particularly in species with the greatest opportunity to even out offspring quality after fledging.

Do changes in reef habitats influence relative predation risk on the juvenile Australasian spiny lobster, Jasus edwardsii (Hutton, 1875)?

Crustaceana ◽  
2015 ◽  
Vol 88 (7-8) ◽  
pp. 839-856 ◽  
Author(s):  
J. Hesse ◽  
J. A. Stanley ◽  
A. G. Jeffs
Keyword(s):  
Predation Risk ◽  
Spatial Scales ◽  
Spiny Lobster ◽  
Habitat Type ◽  
Small Spatial Scale ◽  
Important Species ◽  
Early Juvenile ◽  
Risk Of Predation ◽  
Jasus Edwardsii ◽  
Commercially Important

Kelp habitats are in decline in many temperate coastal regions of the world due to climate change and expansion of populations of grazing urchins. The loss of kelp habitat may influence the vulnerability to predators of the juveniles of commercially important species. In this study relative predation rates for kelp versus barren reef habitat were measured for early juvenile Australasian spiny lobster, Jasus edwardsii (Hutton, 1875), on the northeastern coast of New Zealand using tethering methods. Variation in assemblages of predators over small spatial scales appeared to be more important for determining the relative predation of lobsters, regardless of habitat type. Therefore, the assessment of relative predation risk to early juvenile lobsters between kelp and barren habitats will require more extensive sampling at a small spatial scale, as well as a specific focus on sampling during crepuscular and nocturnal periods when these lobsters are most at risk of predation.

Behavioural responses of voles to simulated risk of predation by a native and an alien mustelid: an odour manipulation experiment

2010 ◽  
Vol 37 (4) ◽  
pp. 273 ◽  
Author(s):  
Karen Fey ◽  
Peter B. Banks ◽  
Hannu Ylönen ◽  
Erkki Korpimäki
Keyword(s):  
Baltic Sea ◽  
Predation Risk ◽  
Myodes Glareolus ◽  
The Baltic Sea ◽  
Short Term ◽  
Behavioural Responses ◽  
Alien Predator ◽  
Risk Of Predation ◽  
The Baltic ◽  
The Impact

Context. Potential mammalian prey commonly use the odours of their co-evolved predators to manage their risks of predation. But when the risk comes from an unknown source of predation, odours might not be perceived as dangerous, and anti-predator responses may fail, except possibly if the alien predator is of the same archetype as a native predator. Aims. In the present study we examined anti-predator behavioural responses of voles from the outer archipelagos of the Baltic Sea, south-western Finland, where they have had no resident mammalian predators in recent history. Methods. We investigated responses of field voles (Microtus agrestis) to odours of native least weasels (Mustela nivalis) and a recently invading alien predator, the American mink (Mustela vison), in laboratory. We also studied the short-term responses of free-ranging field voles and bank voles (Myodes glareolus) to simulated predation risk by alien mink on small islands in the outer archipelago of the Baltic Sea. Key results. In the laboratory, voles avoided odour cues of native weasel but not of alien mink. It is possible that the response to mink is a context dependent learned response which could not be induced in the laboratory, whereas the response to weasel is innate. In the field, however, voles reduced activity during their normal peak-activity times at night as a response to simulated alien-mink predation risk. No other shifts in space use or activity in safer microhabitats or denser vegetation were apparent. Conclusions. Voles appeared to recognise alien minks as predators from their odours in the wild. However, reduction in activity is likely to be only a short-term immediate response to mink presence, which is augmented by longer-term strategies of habitat shift. Because alien mink still strongly suppresses vole dynamics despite these anti-predator responses, we suggest that behavioural naiveté may be the primary factor in the impact of an alien predator on native prey. Implications. Prey naiveté has long been considered as the root cause of the devastating impacts of alien predators, whereby native prey simply fail to recognise and respond to the novel predation risk. Our results reveal a more complex form of naiveté whereby native prey appeared to recognise alien predators as a threat but their response is ultimately inadequate. Thus, recognition alone is unlikely to afford protection for native prey from alien-predator impacts. Thus, management strategies that, for example, train prey in recognition of novel threats must induce effective responses if they are expected to succeed.

scholarly journals PENGARUH RESIN TERHADAP PERUBAHAN WARNA PADA CAT TEMBOK

2019 ◽  
Vol 5 (2) ◽  
pp. 132
Author(s):  
Nurlela Nurlela ◽  
Risnawati Risnawati
Keyword(s):  
Film Thickness ◽  
Vinyl Acetate ◽  
Polyvinyl Acetate ◽  
Color Change ◽  
Color Difference ◽  
Background Color ◽  
Color Changes ◽  
Synthetic Resins ◽  
Color Background

The Influence of Resin against the Change of Color on the Wall PaintThe quality of the paint is determined by the resin used. Synthetic resins for polymer paints are made by combining several monomers to achieve various characteristics. The incorporation of some monomers such as polyvinyl acetate resin, acrylic vinyl resin and acrylic styrene resin which act as a binder can affect the quality of the paint especially the color change. The purpose of this study is to find the color changes that occur on the wall paint by using Poly Styrene Acrylic , Poly Vinyl Acetate and Poly Vinyl Acrylic. From the results of the measurement of color difference, significant color change occurs in the Poly Vinyl Acetate (PVAc) + Poly Vinyl Acrylic (PVA) and Poly Styrene Acrylic (PSA). The results of the quality test of the three resins based on pH test, scrub test and viscosity test, PSA has better quality compared to PVA + PVAc and PVA resin. From the color difference measurement test, some things need to be considered, are temperature, film thickness, substrate color/background color and measurement conditions (measured in wet sample/in plate/dry surface) and test on resin added additive according to the type of each resin.Keywords: Paint, Resin, Color Changes, Poly Vinyl Acetate, Poly Styrene.ABSTRAK Kualitas dari cat sangat ditentukan oleh resin yang digunakan. Resin sintetis untuk cat berupa polimer yang dibuat dengan menggabung beberapa monomer untuk mencapai berbagai karakteristik. Penggabungan dari beberapa monomer seperti resin poli vinil asetat, resin vinil akrilik dan resin stirena akrilik yang berfungsi sebagai pengikat mampu mempengaruhi kualitas cat terutama dari perubahan warna. Tujuan dari penelitian ini adalah untuk mengetahui perubahan warna yang terjadi pada cat tembok dengan menggunakan Poli Stirena Akrilik, Poli Vinil asetat dan Poli Vinil Akrilik. Dari hasil pengukuran perbedaan warna, perubahan warna cukup signifikan terjadi pada resin Poli vinil Asetat (PVAc) + Poli Vinil Akrilik (PVA) dan resin  Poli Stirena Akrilik (PSA). Hasil uji Kualitas cat dari ketiga resin berdasarkan uji pH, uji scrub dan uji viscositas, PSA memiliki kualitas yang lebih baik dibandingkan dengan resin PVA+PVAc dan PVA. Dari pengujian pengukuran perbedaan warna, beberapa hal yang perlu di perhatikan, yaitu suhu, film thickness, warna substrat/background color dan kondisi pengukuran (diukur dalam keadaan wet sample/dalam bentuk plate/dry surface) dan pengujian terhadap resin yang ditambahkan zat aditif yang sesuai dengan tipe masing-masing resin tersebut.Kata Kunci: Cat, Resin, Perubahan Warna, Poli Vinil, Poli Stirena.

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