Artificial surveillance cues do not increase generosity: two meta-analyses

Many studies have seemingly demonstrated that anonymous individuals who are shown artificial cues of being watched behave as if they are being watched by real people. However, several studies have failed to replicate this surveillance cue effect. In light of these mixed results, we conducted two meta-analyses investigating the effect of artificial observation cues on generosity. Overall, our meta-analyses found no evidence to support the claim that artificial surveillance cues increase generosity, either by increasing how generous individuals are, or by increasing the probability that individuals will show any generosity at all. Therefore, surveillance cue effects should be interpreted cautiously.     

Cannibalizing Harmonia axyridis (Coleoptera: Coccinellidae) larvae use endogenous cues to avoid eating relatives

Cannibalism is widespread among many different organisms, and can have both negative and positive fitness consequences. Avoiding eating relatives can minimize negative fitness consequences of cannibalism. Such avoidance requires kin discrimination, but evidence for this ability among cannibals is limited with little data that address the cues used in such discrimination. We examined whether larvae of the ladybird beetle Harmonia axyridis avoid eating their relatives. We further manipulated environmental factors to create individuals that had similar or dissimilar rearing environments to begin to test for endogenous versus exogenous recognition cues. In our experiments, third-instar larvae were much less likely to cannibalize if they were interacting with a relative. Larvae that did cannibalize kin required more encounters, and significantly delayed cannibalism, compared to larvae cannibalizing unrelated individuals. Acquired cues were less important. Even though the different rearing environment resulted in significantly different phenotypic effects, similarity or dissimilarity of rearing environment had no effect on cannibalism, and there was no interaction between environments and relatedness in cannibalism. We suggest that H. axyridis has a well-developed kin discrimination system, and that kin recognition in this ladybird beetle is based on endogenous rather than exogenous cues. We also argue that these cues reflect either direct or indirect genetic effects on larval phenotypes.     

RETRACTED ARTICLE: Latitude affects degree of advancement in laying by birds in response to food supplementation: a meta-analysis

Food supplementation experiments have provided considerable information about the importance of resource availability in timing reproduction. Supplemented birds usually advance breeding over non-supplemented controls. Initial observations suggested that degree of advancement in studies conducted at higher latitudes was less than in those at lower latitudes. We hypothesized that birds at high latitudes are less responsive to the "supplementary" cue of food. We tested this hypothesis using a literature-based meta-analysis of 36 papers which, because several papers presented separate data sets from different years, yielded 56 "studies." We used step-wise regression to determine whether latitude, elevation, the duration of supplementation, and the migratory status of the species predicted the degree to which mean clutch initiation dates of food supplemented birds differed from non-supplemented controls (i.e., effect size = [Formula: see text]). Consistent with our predictions, there was a significant inverse relationship between effect size and latitude: elevation, migratory status, and duration of treatment contributed little to the model. Because the response of animals' reproductive systems to environmental information is mediated by the neuroendocrine system, we discuss two models: (1) the adaptive specialization hypothesis in which higher latitude species that experience a relatively short breeding season have evolved a reliance on photic cues while exhibiting reduced sensitivity to non-photic cues; and (2) the conditional plasticity hypothesis in which an individual might show a marked response to non-photic information if it lived at low latitudes, but be largely driven by photic cues, endogenous rhythms, or both to the relative exclusion of non-photic information if it lived at higher latitudes.     

Predation risk perception and food scarcity induce alterations of life-cycle traits of the mosquito Culex pipiens

Abstract.  1. Predators may affect prey populations by direct consumption, and by inducing defensive reactions of prey to the predation risk. Food scarcity frequently has effects on the inducible defences of prey, but no consistent pattern of food–predation risk interaction is known.
2. In this study the combined effect of food shortage and predation-risk perception in larvae of the mosquito Culex pipiens was investigated. Water exposed to the aquatic predator bug Notonecta glauca was used as a source of predation intimidation. Mosquito larvae were reared in three different media containing either no predator cues or the cues of N. glauca that had been fed on either C. pipiens larvae or on Daphnia magna . Food was provided in favourable or limited amount for these set-ups.
3. The results showed that chemical cues from the predators fed with prey's conspecifics caused a decreased survival, delayed pre-imaginal development, and reduction in body size of emerged mosquitoes, whereas chemical cues from predators fed with D. magna caused only delayed development. Food scarcity significantly exacerbates the negative effect of the predator cues on pre-imaginal development of C. pipiens . Effects of the cues on larval development and body size of imagoes are significantly stronger for females than for males.
4. The present study suggests that when food is limited, predators can affect population dynamics of prey not only by direct predation, but also by inducing lethal and sublethal effects due to perception of risk imposed by chemical cues. To understand the effects of predators on mosquito population dynamics, environmental parameters such as food deficiency should be considered.     

Is love in the air or at first sight? Mate finding cues used by sympatric male velvet ants (Hymenoptera: Mutillidae)

Mate finding has been examined in a wide range of hymenopteran families, with the greatest knowledge from social species and parasitoids used in pest management. Velvet ants (Hymenoptera: Mutillidae) provide a unique system to study mate finding because short‐lived flying males must find solitary, wingless females that have spatially and temporally dispersed emergence. Based on limited field observations, it is thought that male velvet ants may use visual, chemical, and vibratory cues for mate finding, though there have been no controlled experiments to test these hypotheses. Using choice experiments, this study aims to determine the role of visual and airborne chemical cues used in female detection by three sympatric species of Dasymutilla males. We find that visual cues are not used for initial female detection and that airborne chemicals are sufficient for female detection. We also discover that males readily approach females of different species, indicating airborne chemicals are not used for species recognition. Despite the lack of discrimination by males, we determined that the sympatric, morphologically similar species show no genetic introgression, and therefore some other isolating mechanism must be at play after males make initial contact with the females.     

Effects of substratum and conspecific adults on the metamorphosis of Chasmagnathus granulata (Dana) (Decapoda: Grapsidae) megalopae

The ability of marine invertebrate larvae to delay their metamorphosis in the absence of adequate environmental cues has been reported for numerous sedentary and sessile species. In the present study, the effect of various substrata and the presence of conspecific adults on the metamorphosis of a mobile species, the crab Chasmagnathus granulata, was evaluated. The duration of the megalopa stage in experiments with six different substrata and in the presence or absence of conspecific adults was compared in a laboratory study. In addition, the influence of natural substrata was compared with that of artificial substrata of similar grain size or texture. In a further experiment, the two most effective cues (natural mud and conspecific adults) were tested as single vs. combined factors. Natural mud and unidentified chemical cues from conspecific adults had the strongest accelerating effects on development duration to metamorphosis. With the exception of nylon threads (artificial filamentous substratum), none of the artificial substrata had a significant effect on the duration of the megalopa stage. Simultaneous exposure to natural mud and water containing chemical cues from conspecific adults accelerated metamorphosis more than each of these factors separately. Megalopae that were reared without a substratum (control) delayed their metamorphosis by 29% (about 3 days) compared with those in simultaneous contact with natural mud and rearing water of adult conspecifics. The results indicate that the metamorphosis of the megalopa of C. granulata is influenced by the presence or absence of environmental stimuli that are associated with the preferred adult habitat.     

Do house mice use UV cues when foraging?

Research on the behavioural ecology of ultraviolet (UV-A, wavelengths of 320–400 nm, hereafter: UV) sensitivity in terrestrial vertebrates has mainly focused on sexual signalling and foraging in birds and reptiles, whereas the fact that some rodents are also sensitive to UV light has been somewhat ignored. Here, we present the results of two behavioural experiments, which tested whether rodents use UV cues in foraging. In the first experiment we asked whether the colour contrast in the UV waveband is used as a foraging cue. House mice were offered UV-reflecting and UV-absorbing artificial food items in two different illuminations where UV light was either present or absent. The food items were offered to two groups of mice, one group on a UV-reflecting and the other on a UV-absorbing background. The second experiment investigated more specifically whether UV cues are especially important in dawn and dusk when short wavelengths are high in the proportion of available light. House mice showed no preference between the food items regardless of illumination or background. Therefore, our results indicate that house mice do not use UV cues in foraging.     

Frog breeding pond selection in response to predators and conspecific cues

Predators are a major influence on the breeding site selection decisions of anurans. Many species actively avoid breeding in habitat with predators when given the choice between predator and predator‐free sites. However, certain factors such as site fidelity or conflicting cues may preclude avoidance behavior. We conducted two experiments examining how western chorus frogs, Pseudacris triseriata, respond to predators, western mosquitofish, Gambusia affinis, using an array of artificial ponds located at two field sites. In one experiment, we added G. affinis to half of our experimental ponds and monitored subsequent colonization by frogs. We found that frogs laid significantly fewer eggs in ponds with fish compared to fishless ponds. In another experiment, we introduced an additional cue to complicate the decision‐making process and monitored colonization of ponds in response to treatments of conspecific breeding cues only (eggs), predators (G. affinis) only, and conspecific cues and predators. We found no significant differences in number of eggs deposited among these three treatments. Based on these results, P. triseriata does not always exhibit complete avoidance of fish predators, and avoidance may vary based on factors such as site fidelity or dispersal costs. This study represents a step toward understanding how multiple biotic factors at a breeding pond may influence anuran site selection behavior in the field.     

Pollinator attraction in Cornus capitata (Cornaceae): the relative role of visual and olfactory cues

Aims It is generally accepted that visual displays and floral scent play important roles in communication between flowering plants and their pollinators. However, the relative role of visual and olfactory cues in pollinator attraction is largely unknown. In this study, we determined the roles of both types of cue in attracting pollinators to Cornus capitata, a medium sized tree with each capitulum surrounded by four large, white, petaloid bracts.Methods Pollinator observations and pollination experiments were conducted in a natural population; the inflorescences' visual and olfactory signals were characterized by spectral and chemical analyses; the responses of pollinators to visual and olfactory cues were tested using dual-choice behavioural bioassays; the relative roles of visual and olfactory cues in pollinator attraction were tested by comparing the responses of pollinators to inflorescences subjected to three experimental treatments (intact, all bracts removed, and capitulum removed) within the natural population.Important findings For fruit set, C. capitata is entirely dependent on pollinators, with a bee, Anthophora sp., being the main pollinator. Bracts present high colour distance and green contrast against the leaves. Twelve volatile compounds in the floral scent were detected, most of which have previously been reported to be attractive to a broad spectrum of bee species. Behavioural bioassays showed that both, visual cues alone and olfactory cues alone, are attractive to pollinating bees. However, visual cues alone attracted significantly more approaches than olfactory cues alone, while olfactory cues alone elicited a significantly higher landing percentage than visual cues alone. The finding suggests that, in the C. capitata – Anthophora sp. interaction, visual cues are mainly used for location from long distances, while olfactory cues mainly aid landing from short distances. Our results indicate that different modalities of floral cues should be considered together to understand fully the communication between flowering plant and pollinators.     

What the honeybee sees: a review of the recognition system of Apis mellifera

Abstract. For many years, two opposing theories have dominated our ideas of what honeybees see. The earliest proposal based on training experiments was that bees detected only simple attributes or features, irrespective of the actual pattern. The features demonstrated experimentally before 1940 were the disruption of the pattern (related to spatial frequency), the area of black or colour, the length of edge, and the angle of orientation of a bar or grating. Cues discovered recently are the range, and radial and tangential edges, and symmetry, relative to the fixation point, which is usually the reward hole. This theory could not explain why recognition failed when the pattern was moved. In the second theory, proposed in 1969, the bee detected the retinotopic directions of black or coloured areas, and estimated the areas of overlap and nonoverlap on each test pattern with the corresponding positions in the training pattern. This proposal explained the progressive loss of recognition as a test pattern was moved or reduced in size, but required that the bees saw and remembered the layout of every learned pattern and calculated the mismatch with each test image. Even so, the same measure of the mismatch was given by many test patterns and could not detect a pattern uniquely. Moreover, this theory could not explain the abundant evidence of simple feature detectors. Recent work has shown that bees learn one or more of a limited number of simple cues. A newly discovered cue is the position, mainly in the vertical direction, of the common centre (centroid) of black areas combined together. Significantly, however, the trained bees look for the cues mentioned above only in the range of places where they had occurred during the training. These two observations made possible a synthesis of both theories. There is no experimental evidence that the bees detect or re-assemble the layout of patterns in space; instead, they look for a cue in the expected place. With an array of detectors of the known cues, together with their directions, this mechanism would enable bees to recognize each familiar place from the coincidences of cues in different directions around the head.     

Stimulation of metamorphosis in an estuarine crab, Chasmagnathus granulata (Dana, 1851): temporal window of cue receptivity

The larvae of most benthic marine invertebrate species must develop for a minimum of time in the plankton before they become competent for settlement and metamorphosis in response to stimulating external cues. In an experimental laboratory study, we identified the temporal window of cue receptivity within the moulting cycle of the megalopa stage of an estuarine crab, Chasmagnathus granulata Dana. This species shows an export strategy including an early larval transport to coastal marine waters where zoeal development takes place, followed by the return of the megalopa stage to brackish habitats where the adults live. In two series of experiments (A, B), megalopae were exposed for differential periods to a combination of metamorphosis-stimulating cues which had previously been found effective (seawater conditioned with adult odor and presence of mud). In experimental series A, these cues were added on successively later days of the moulting cycle, while series B comprised treatments in which the cues were provided from the first day (postmoult) and removed on successively later days of the moulting cycle. Each series of experiments was repeated with larvae originating from two different females (F1, F2). The average development time of megalopae kept continuously in the presence of cues (control experiments, C1) ranged in the two hatches from 9.3 to 9.6 days. In the inverse controls where no cue was added at any time (C2), megalopal development to metamorphosis took on average 11.2-12.0 days. In series A, development duration in treatments with exposure to the cues commencing within 3-4 days after moulting was not significantly different from that in the permanently exposed C1 controls. Later beginning of the exposure, by contrast, had no stimulating effect (significant delay compared to C1, no significant difference from unexposed control, C2). In series B, no significant differences in development time were observed between the C1 controls and treatments with an initial exposure for a minimum of 4 or 6 days of the moulting cycle (F1, F2, respectively). Shorter initial periods of exposure had no metamorphosis-stimulating effects (no significant difference from C2). In conclusion, our results from both experiments suggest that the megalopa stage of C. granulata is most receptive of stimulating cues during a period lasting from ca. one third to one half of the moulting cycle, which coincides with the transition between stages C (intermoult) and D₀ (early premoult) of Drach's classification system. This suggests an interaction of extrinsic stimulating cues with intrinsic (hormonal) factors involved in the control of the moulting cycle.     

Interaction between positional but not between non-positional cues in human predictive learning

Four experiments with human subjects examined the cue-interaction effects using a computer-controlled predictive learning task. In Phase 1, subjects learned that cue P was consistently associated with the occurrence of an outcome (P+), whereas cue N was never followed by the outcome (N−). In Phase 2, two neutral cues, R and I, were compounded with P and N, respectively. Each compound was followed by the outcome (PR+ and NI+). Thus, cue R was compounded with the already predictive cue P, whereas cue I was compounded with the non-predictive cue N. In each phase, subjects rated the contingency between the different cues and the outcome. In experiments 1 and 2, the spatial position of the cues was fixed, whereas it was variable in experiments 3, 4a and 4b. Verbal cues were used in experiments 1–3, whereas the cues consisted of geometrical figures in experiments 4a and 4b. Evidence for cue interaction, as indicated by giving cue I a higher contingency rating than cue R after or during Phase 2, was only found under the conditions of experiments 1 and 2. The results indicate that the use of positional cues facilitates the occurrence of cue-interaction effects. Possible reasons for this finding are discussed.     

Are dogs able to recognize their handler's voice? A preliminary study

Abstract

A number of studies have dealt with the ability of dogs to rely on olfactory cues to recognize their owner or handler. However, in the absence of these cues (e.g., when working at a distance from their owner) dogs have to use other senses to interact with their owner. Considering the high sensitivity of their auditory system, we can hypothesize that dogs are able to use vocal cues for this purpose. Certainly, it is commonly assumed that dogs can discriminate between people on the basis of their voice, and yet there is a clear lack of empirical data on this subject. The present study assesses the importance of the handler's olfactory and visual cues versus the importance of his/her vocal cues to the working behavior of dogs. I compare the ability of working dogs to obey different vocal commands issued either by their handler (HV) or by a stranger (SV) via loudspeakers in different olfactory contexts: presence of their handler (H) or of a stranger (S). The dogs' performance (percentage of correct responses) decreased when the acoustic cues were modified (H+HV tended to differ from the H+SV—p = 0.09—and differed from the S+SV conditions—p = 0.05) but not when only the olfactory cues were changed (no difference between H+HV and S+HV conditions—p > 0.1). Consequently, we can assume that dogs rely, at least in part, on acoustic parameters of voices to recognize and cooperate with their handler.     

Predator-induced changes in morphology of a prey fish: the effects of food level and temporal frequency of predation risk

In a series of experiments, we investigated the effects of food availability and risk frequency on the dynamics of predator-induced changes in growth and morphology of prey fish using goldfish (Carassius auratus) as our test species. In experiment 1, we fed goldfish high or low food rations and exposed them to either alarm cues from conspecifics, cues from swordtails or a water control. After 60 days, goldfish in the alarm cue treatment significantly increased their body depth and body weight but had smaller body length than goldfish exposed to swordtails cues or water, likely reducing their vulnerability to gape-limited predators. Importantly, food level had an impact on the amplitude of the morphological changes. In experiment 2, goldfish were exposed to two different frequencies of predation cues or a water control for 50 days. The cues were either continued or discontinued from day 51 to 100, and all cues were resumed from day 101 to 150. We found that goldfish exposed to predation cues increased their depth and weight at a faster rate than did the goldfish exposed to water, and of particular significance was the fact that frequency of risk had an effect on the amplitude of the change. When the cues were interrupted, the increase in growth rate parameters was reduced to the level of the goldfish exposed to water. However, when the cues were resumed, the rate increased to match the growth rate of the goldfish that were continuously exposed to the cues. Finally, we staged encounters between goldfish of differing morphologies and yellow perch (Perca flavescens) and found that deep-bodied goldfish had better survival than the shallow-bodied ones. These experiments illustrate the dynamic nature of inducible morphological defences.     

Fiber alignment directs cell motility over chemotactic gradients

The ability of tissue engineered scaffolds to direct cell behavior is paramount for scaffold design. Cell migration can be directed by various methods including chemical, adhesive, mechanical, and topographical cues. Electrospinning has emerged as a popular method to control topography and create fibrous scaffolds similar to that found in extracellular matrix. One major hurdle is limited cell infiltration and several studies have explored methods to alter electrospun materials to increase scaffold porosity; however, uniform cell distributions within scaffolds is still limited. Towards this, we investigated the motility of HUVECs on a model system of electrospun hyaluronic acid fibers under a gradient of VEGF and found that topographical cues dominate cell motility direction. Using time‐lapse microscopy, cell aspect ratio, and migration angle were measured; cells were directed in a chemical gradient and/or on aligned electrospun fibers. Measurements of the persistence time demonstrated an additive effect of the chemical gradient and fiber alignment. However, when fibers were aligned perpendicular to a chemical gradient, cells were directed by fiber alignment and there was no effect of the chemical gradient. These results suggest that topographical cues may be more influential than chemical cues in directing cell motility and should be considered in material design. Biotechnol. Bioeng. 2013; 110: 1249–1254. © 2012 Wiley Periodicals, Inc.     

Female German cockroaches join conspecific groups based on the incidence of auditory cues

Insects deciding whether to approach and join a group of conspecifics may utilize olfactory and auditory signals, or cues, from that group as indicators of its size or the suitability of its shelter. Here we show (1) that German cockroaches, Blattella germanica L. (Dictyoptera: Blattellidae), in groups wing‐fan; (2) that the incidence of wing‐fanning (WF) increases proportionately to group size; and (3) that gravid females utilize auditory cues associated with WF behaviour when they decide whether or not to enter a shelter. In binary choice arena bioassays, proportionately more gravid females avoided shelters associated with play‐back of high‐incidence male‐ or female‐produced WF sound, indicating a high‐density group of conspecifics, but sought shelters associated with play‐back of low‐incidence WF sound, indicating a low‐density group of conspecifics. These auditory cues seem to convey information on group size or density, avoid sensory fatigue in enclosed environments, and allow sonotactic orientation to the group's location.     

水生生态环境中捕食信息素的生态学效应

捕食信息素是捕食者释放的,能够引发猎物反捕食反应的化学信号。在水生生态系统中,捕食信息素在捕食者和猎物之间信息传递及协同进化过程中发挥着重要的作用,其生态学效应在国际上受到广泛关注。捕食信息素的来源有多种形式,研究中常使用养殖过捕食者的水溶液作为捕食信息素的来源。捕食信息素的作用效果受到捕食者和猎物的种类、信息素的浓度、观察的指标等多方面因素的影响。捕食信息素可以对水生生物的行为、形态和生活史特征等方面造成影响。水生生物通过感知捕食信息素来提前预知潜在的被捕食风险,并作出适应性调整,以降低被捕食的风险。在某些情况下,捕食信息素可以与污染物产生交互作用,从而干扰污染物对水生生物的毒性。对水生环境中捕食信息素的研究现状做了综述,介绍了当前对捕食信息素来源和理化性质等本质问题的认识,总结捕食信息素对水生生物行为、形态和生活史特征的影响,以及捕食信息素对污染物毒性的干扰,并分析了这一研究领域尚存在的困难和今后的研究方向。加强对捕食信息素的研究,将为解析水生环境中捕食者和猎物的生态关系提供新依据。     

Response to conspecific and heterospecific alarm cues by pumpkinseeds in simple and complex habitats: field verification of an ontogenetic shift

Three focal size classes [small (<40 mm, standard length, L _S), medium (40–80 mm L _S) and large (>80 mm L _S)] of pumpkinseed Lepomis gibbosus were exposed to conspecific or one of three heterospecific chemical alarm cues under one of three levels of habitat complexity (low, intermediate and high). Under low and intermediate habitat complexities, pumpkinseeds <80 mm L _S exhibited a significant antipredator response when exposed to the chemical alarm cues of heterospecific prey guild members (largemouth bass Micropterus salmonides and hypoxanthine‐3‐ N ‐oxide, the putative Ostariophysan alarm 'pheromone'), while pumpkinseeds >80 mm L _S exhibited a foraging response. Under highly complex habitats, pumpkinseeds of all three size classes exhibited an antipredator response. Moreover, under all three habitat conditions, pumpkinseeds of all size classes exhibited an antipredator response to conspecific alarm cues. There was no change in behaviour under any treatment combination in response to an allopatric heterospecific control (swordtails Xiphophorus helleri ). These results provide the first field verification of the size dependent use of chemical alarm cues by centrarchids and demonstrate that microhabitat complexity significantly influences the threat‐sensitive use of these cues.     

Mate preference for multiple cues: interplay between male and nest size in the sand goby, Pomatoschistus minutus

Female mating preferences are often based on more than one cue.In empirical studies, however, different mate choice cues aretypically treated separately ignoring their possible interactions.In the current work, we studied how male body size and sizeof the male's nest jointly affect mate preferences of femalesand gobies, Pomatoschistus minutus. The females were givena binary choice between males that differed either in body sizeor size of their nest or both. We found that neither body sizenor size of the nest alone affected male attractiveness, buttogether these 2 cues had a significant effect. Specifically,large males were more popular among females when they had alarge nest than when they occupied a small nest. The resultssuggest that if interaction effects between multiple mate choicecues are not considered, there is a danger of ignoring or underestimatingthe importance of these cues in sexual selection by female choice.