Reduced avian predation on an ultraviolet-fluorescing caterpillar model

Many caterpillars exhibit patterns of ultraviolet (UV) fluorescence, although its purpose is unclear. We used realistic plasticine models of a fluorescing caterpillar species, the Polyphemus moth, Antheraea polyphemus (Lepidoptera; Saturniidae), adorned with fluorescent paint treatments and unpainted controls to quantify bird predation in two hardwood forested regions of New York State, United States of America. In separate field studies, significantly more birds struck deployed model caterpillars that had no UV fluorescence. More strikes on unpainted and clear paint treatments suggest paint itself did not impact predation, whereas similar predation attempts on bird and human-visible fluorescent dummies suggest that UV fluorescence and not UV reflectance was responsible for the observed effect. A second study found the dummy’s location on the tree was also important, but the low number of bird strikes limited analyses. Although our results do not identify a mechanism, fluorescence may function to deter or avoid predation. Our study contributes to a growing body of work investigating the importance of UV patterns in arthropods and highlights a potentially fruitful area of future research on predator–prey relations.

Predation on Common Wall Lizards: Survival Probabilities of Melanic Individuals

For estimation of predation plasticine models of prey animals are often used, because the soft material preserves imprints left by predators. We assumed that melanic common wall lizards (Podarcis muralis) disappear by selective predation faster than cryptic individuals and habitat features have important role in this process. We studied the survival probabilities of cryptic and melanic colored plasticine common wall lizard models in habitats with different background coloration on selected places near the city of Pécs (south Hungary), where melanic common wall lizards had been observed earlier. Contrary to our expectations the daily survival rates of melanic plasticine common wall lizards were somewhat higher in all three locations (sandstone quarry, stone wall, coal pit) than those of the cryptic ones, but these differences were not significant. Predators were mostly mammals, which left more marks on plasticine models than birds, but we could not show a preference of the body parts of prey. We concluded that rare occurrence of melanic common wall lizards in habitats near the city of Pécs is not due to predation pressure.

Seasonal variations in bird selection pressure on prey colouration

The direction and strength of selection for prey colouration by predators vary in space and time and depend on the composition of the predator community. We tested the hypothesis that bird selection pressure on prey colouration changes through the season due to changes in the proportion of naïve juvenile individuals in the bird community, because naïve and educated birds differ in their responses to prey colours. Bird predation on caterpillar-shaped plasticine models in two boreal forest sites increased sevenfold from early summer to mid-summer, and the time of this increase coincides with the fledging of juvenile birds. In early summer, cryptic (black and green) models were attacked at fivefold higher rates compared with conspicuous (red and yellow) models. By contrast, starting from fledging time, cryptic and conspicuous models were attacked at similar rates, hinting at a lower selectivity by naïve juvenile birds compared with educated adult birds. Cryptic models exposed in a group together with conspicuous models were attacked by birds at a threefold lower rate than cryptic models exposed singly, thus supporting the aposematic commensalism hypothesis. However, this effect was not observed in mid- and late summer, presumably due to the lack of avoidance of conspicuous prey by the juvenile birds. We conclude that selection pressure on prey colouration weakens considerably when naïve birds dominate in the community, because the survival advantages of aposematic colouration are temporarily lost for both the conspicuous and their neighbouring cryptic prey.

European Higher Education Students: Contested Constructions

There are currently over 35 million students within Europe and yet, to date, we have no clear understanding of the extent to which understandings of ‘the student’ are shared across the continent. Thus, a central aim of this article is to investigate how the contemporary higher education student understands their own role, and the extent to which this differs both within nation-states and across them. This is significant in terms of implicit (and sometimes explicit) assumptions that are made about common understandings of ‘the student’ across Europe – underpinning, for example, initiatives to increase cross-border educational mobility and the wider development of a European Higher Education Area. Drawing on data from students across Europe – and particularly plasticine models participants made to represent their understanding of themselves as students – we argue that, in many cases, there is an important disconnect between the ways in which students are constructed within policy, and how they understand themselves. The models produced by participants typically foregrounded learning and hard work rather than more instrumental concerns commonly emphasised within policy. This brings into question assertions made in the academic literature that recent reforms have had a direct effect on the subjectivities of students, encouraging them to be more consumerist in their outlook. Nevertheless, we have also shown that student conceptualisations differ, to some extent, by nation-state, evident particularly in Spain and Poland, and by institution – most notably in England and Spain, which have the most vertically differentiated higher education systems. These differences suggest that, despite the ‘policy convergence’ manifest in the creation of a European Higher Education Area, understandings of what it means to be a student in Europe today remain contested.

Landscape drivers and effectiveness of pest control by insectivorous birds in a landscape-dominant woody crop

Avian-mediated pest control is a significant ecosystem service with important economic implications. However, there is an overall paucity of experimental information about how landscape simplification affect its current level. Information on pest control by birds is missing in some permanent agroecosystems of worldwide importance, like olive orchards, that dominate vast areas in the Mediterranean region.We assess the effectiveness of insectivorous birds for controlling the two main pest insects in olive orchards and explore the effects of landscape complexity and distance to semi-natural patches on avian insectivore abundance and pest control. For this, we combine bird surveys with field experiments (branch exclusions and pest plasticine models) at the regional scale.Landscape heterogeneity increased the abundance and richness of insectivorous birds, which were also more abundant and diverse in semi-natural patches, compared to the farm olive matrix. Experiments evidenced that pest control by birds (measured as attack rates to plasticine models and pest damage) in the studied olive orchards is negligible, while pests were overall abundant and pest damage was high on most farms. This raises alarms about the status of avian pest control in this agroecosystem.Although landscape heterogeneity increased the abundance/richness of insectivorous birds, and favored some forest species, insectivorous bird abundance seems diluted in relation to prey availability in all landscapes. Thus, pest control by birds seems currently unsuccessful in olive orchards. Our results might be evidencing the loss of an ecosystem service due to a generalized massive decline of common and forest insectivorous birds.Key messageOlive orchards dominate extensive areas causing important landscape simplification.Insectivorous birds are more abundant in semi-natural patches within olive farms.Field experiments show a low impact of birds on olive pests and damage.Avian-mediated pest biocontrol seems diluted by limited suitable habitat for birds.Agri-environmental measures should focus on increasing landscape complexity.

The yellow-legged gull as a predator of lizards in Balearic Islands

Lizards and gulls cohabit in several Mediterranean islands. The yellow-legged gull, Larus michahellis, was found to prey several vertebrate species. However, precise information about the interaction between gulls and other vertebrates, particularly with lizards is still scarce. The Balearic lizard, Podarcis lilfordi, shares several coastal islets with the yellow-legged gull. Using two different sources of information, we studied the interaction of both species in Colom Island (Menorca, Balearic Islands, Spain). We studied the diet of the yellow-legged gull and learnt that the Balearic lizard is not a common prey of the yellow-legged gull. On the other hand, we studied the potential predation pressure of gulls on lizards, using plasticine models of lizards. We did two different experiments from which we can conclude that yellow-legged gulls rarely attack lizards and, consequently, cannot be considered a major threat for this endemic lizard species, at least in the population under study. Finally, we obtained evidence that plasticine models can only be employed with caution to assess predation pressure of opportunistic scavengers, much as gulls are. The majority of marks on models were not the consequence of true attacks by gulls, but the result of ground exploratory behaviour of gulls in search of any edible matter. Therefore, contrary to popular belief, in the case of the yellow-legged gull, the proportion of marked models would be an indication of ground-based wandering activity, rather than a result of its predation pressure on lizards.

Comments on Guimarães & Sawaya. Pretending to be venomous: is a snake's head shape a trustworthy signal to a predator?

Several species of non-venomous snake are known to flatten their heads when disturbed, and this behaviour has been suggested to be a mimicry of vipers (Arnold & Ovenden 2002, Hailey & Davies 1986, Young et al. 1999). Using plasticine models, Guimarães & Sawaya (2011) tested the antipredatory function of a triangular head shape in snakes. Their article presents the first published empirical experiment testing the adaptive significance of vipers' triangular head shape. Guimarães & Sawaya (2011) found no support for the viper mimicry hypothesis. Accordingly, they concluded that ‘the shape of [the] head seemed not to confer advantage itself’. Although the use of plasticine models is a generally accepted method of testing predation pressure on snakes, we argue that the experiment may have failed to find the antipredatory function of triangulation due to the pooling of attacks by mammalian and avian predators. Mammals generally rely on olfactory cues during foraging. Plasticine has a strong odour which does not resemble the odour of any prey species. It is thus unlikely that mammals would treat snake replicas as true snakes.

The snake head-shape signal: a reply to Valkonen & Mappes

It has already been suggested that snake head triangulation might be related to mimicry of the head shape of vipers (Greene & McDiarmid 2005, and references therein). Until very recently, this hypothesis has never been experimentally tested. We first tested the hypothesis of snakes’ head shape as a dangerous signal to predators by use of plasticine models (Guimarães & Sawaya 2011). We suggested in that study that shape of the head does not confer advantage itself but may work in synergy with a set of traits including colour and behavioural displays that warn and discourage predator attacks.

Mathematical and Physical Modeling of Soft Cobbing Process of Hot Rolling Steels

The soft cobbing, used in steel’s continuous casting, is widely applying in technologies of rolled metal manufacturing. It is important to know ingot’s stress-strain state and dynamics of ingot’s changes while cobbing, when there is a liquid metal in the centre of section. The complex questions of numerical modeling of soft cobbing process and experimental investigation on physics plasticine models are considered in presented work. The analysis of findings is presented in the article.

Seeing through the lizard’s trick: do avian predators avoid autotomous tails?

Counter-adaptations of predators towards their prey are a far less investigated phenomenon in predator-prey interactions. Caudal autotomy is generally considered an effective last-resort mechanism for evading predators. However, in victim-exploiter relationships, the efficacy of a strategy will obviously depend on the antagonist’s ability to counter it. In the logic of the predator-prey arms race, one would expect predators to develop attack strategies that minimize the chance of autotomy of the prey and damage on the predator. We tested whether avian predators preferred grasping lizards by their head. We constructed plasticine models of the Italian wall lizard (Podarcis sicula) and placed them in natural habitat of the species. Judging from counts of beak marks on the models, birds preferentially attack the head and might also avoid the tail and limb regions. While a preference for the head might not necessarily demonstrate tail and limb avoidance, this topic needs further exploration because it suggests that even unspecialised avian predators may see through the lizard’s trick-of-the-tail. This result may have implications for our understanding of the evolution of this peculiar defensive system and the loss or decreased tendency to shed the tail on island systems with the absence of terrestrial predators.