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Christina G. Halpin

Bio: Christina G. Halpin is an academic researcher from Newcastle University. The author has contributed to research in topics: Aposematism & Predation. The author has an hindex of 11, co-authored 18 publications receiving 456 citations.

Papers
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Journal ArticleDOI
TL;DR: The aim of the review is to promote the view that predators do not simply learn to avoid aposematic prey, but rather make adaptive decisions about both when to gather information about defended prey and when to include them in their diets.
Abstract: The question, "Why should prey advertise their presence to predators using warning coloration?" has been asked for over 150 years. It is now widely acknowledged that defended prey use conspicuous or distinctive colors to advertise their toxicity to would-be predators: a defensive strategy known as aposematism. One of the main approaches to understanding the ecology and evolution of aposematism and mimicry (where species share the same color pattern) has been to study how naive predators learn to associate prey’s visual signals with the noxious effects of their toxins. However, learning to associate a warning signal with a defense is only one aspect of what predators need to do to enable them to make adaptive foraging decisions when faced with aposematic prey and their mimics. The aim of our review is to promote the view that predators do not simply learn to avoid aposematic prey, but rather make adaptive decisions about both when to gather information about defended prey and when to include them in their diets. In doing so, we reveal what surprisingly little we know about what predators learn about aposematic prey and how they use that information when foraging. We highlight how a better understanding of predator cognition could advance theoretical and empirical work in the field.

107 citations

Journal ArticleDOI
TL;DR: The aim of this review is to examine the form and function of multimodal warning displays, and evaluate the evidence for different functional hypotheses that can explain their widespread evolution.
Abstract: Multimodal defensive displays are commonplace, with prey combining conspicuous coloration, sounds, odours and other chemical emissions to deter predators. These components can signal to predators in multiple signal modalities to warn them that prey are defended. The aim of our review is to examine the form and function of multimodal warning displays. Data collected from the literature on multimodal insect warning displays show the degree of complexity and diversity that needs to be explained, and we identify patterns in the data that may be worthy of more rigorous investigation. We also provide a theoretical framework for the study of multimodal warning displays, and evaluate the evidence for different functional hypotheses that can explain their widespread evolution. Our review highlights that whilst multimodal warning displays are well documented, particularly in insects, we lack a good understanding of their function in natural predator–prey systems.

100 citations

Journal ArticleDOI
TL;DR: It is found that European starlings increased their consumption of mealworm, Tenebrio molitor, prey containing quinine when the ambient temperature was reduced below their thermoneutral zone from 20 °C to 6 °C, which suggests that conspicuous coloration may be more costly at lower temperatures, and that aposematic prey may need to invest more in chemical defences as temperatures decline.

42 citations

Journal ArticleDOI
TL;DR: It is found that birds ate fewer defended prey, and less quinine, when undefended prey were large compared with when they were small, but that the size of the defended prey had no effect on the numbers eaten, suggesting colour signals may be more salient to predators than size differences.

40 citations

Journal ArticleDOI
TL;DR: It is shown that European starlings (Sturnus vulgaris) increase their intake of a toxic prey type when the nutritional content is artificially increased, and decrease their intake when nutritional enrichment is ceased, demonstrating that birds can detect the nutritionalcontent of toxic prey by post-ingestive feedback, and use this information in their foraging decisions, raising new perspectives on the evolution of prey defences.
Abstract: Avian predators readily learn to associate the warning coloration of aposematic prey with the toxic effects of ingesting them, but they do not necessarily exclude aposematic prey from their diets. By eating aposematic prey ‘educated’ predators are thought to be trading-off the benefits of gaining nutrients with the costs of eating toxins. However, while we know that the toxin content of aposematic prey affects the foraging decisions made by avian predators, the extent to which the nutritional content of toxic prey affects predators' decisions to eat them remains to be tested. Here, we show that European starlings (Sturnus vulgaris) increase their intake of a toxic prey type when the nutritional content is artificially increased, and decrease their intake when nutritional enrichment is ceased. This clearly demonstrates that birds can detect the nutritional content of toxic prey by post-ingestive feedback, and use this information in their foraging decisions, raising new perspectives on the evolution of prey defences. Nutritional differences between individuals could result in equally toxic prey being unequally predated, and might explain why some species undergo ontogenetic shifts in defence strategies. Furthermore, the nutritional value of prey will likely have a significant impact on the evolutionary dynamics of mimicry systems.

39 citations


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30 Apr 1984
TL;DR: A review of the literature on optimal foraging can be found in this article, with a focus on the theoretical developments and the data that permit tests of the predictions, and the authors conclude that the simple models so far formulated are supported by available data and that they are optimistic about the value both now and in the future.
Abstract: Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

2,709 citations

Journal ArticleDOI
04 Aug 2017-Science
TL;DR: A roadmap of technological advances and key questions for the future of animal coloration research are provided, to identify hitherto unrecognized challenges for this multi- and interdisciplinary field.
Abstract: Coloration mediates the relationship between an organism and its environment in important ways, including social signaling, antipredator defenses, parasitic exploitation, thermoregulation, and protection from ultraviolet light, microbes, and abrasion. Methodological breakthroughs are accelerating knowledge of the processes underlying both the production of animal coloration and its perception, experiments are advancing understanding of mechanism and function, and measurements of color collected noninvasively and at a global scale are opening windows to evolutionary dynamics more generally. Here we provide a roadmap of these advances and identify hitherto unrecognized challenges for this multi- and interdisciplinary field.

459 citations

Journal ArticleDOI
TL;DR: The take-home message is that variability in performance in cognitive tasks does not necessarily demonstrate individual variation in cognitive ability, and that the authors need to both design more stringent cognitive tests and be more cautious in their interpretation.
Abstract: Across a range of disciplines, researchers are becoming increasingly interested in studying the variation in cognitive abilities found within populations. Behavioral ecology is no exception: the pursuit to understand the evolution of cognition has lead to a rapidly expanding literature that uses various tasks to measure individuals’ cognitive abilities. While this is an exciting time, we are concerned that without being clearer as to the cognitive abilities under test it will be difficult to design appropriate experiments and the interpretation of the data may be unsound. The aim of this review is 3-fold: 1) to highlight problems with designing tasks for measuring individual variation in cognitive abilities and interpreting their outcomes; 2) to increase awareness that noncognitive factors can cause variation in performance among individuals; and 3) to question the theoretical basis for thinking that performance in any cognitive task should necessarily correlate with a measure of fitness. Our take-home message is that variability in performance in cognitive tasks does not necessarily demonstrate individual variation in cognitive ability, and that we need to both design more stringent cognitive tests and be more cautious in their interpretation.

224 citations

Journal ArticleDOI
TL;DR: The history of the study of complexity in animal communication, issues relating to defining and classifying multi-modal signals, and particular issues to consider with multimodal (as opposed to multicomponent unimodal) communication are discussed.
Abstract: Though it has long been known that animal communication is complex, recent years have seen growing interest in understanding the extent to which animals give multicomponent signals in multiple modalities, and how the different types of information extracted by receivers are interpreted and integrated in animal decision-making. This interest has culminated in the production of the present special issue on multimodal communication, which features both theoretical and empirical studies from leading researchers in the field. Reviews, comparative analyses, and species-specific empirical studies include manuscripts on taxa as diverse as spiders, primates, birds, lizards, frogs, and humans. The present manuscript serves as both an introduction to this special issue, as well as an introduction to multimodal communication more generally. We discuss the history of the study of complexity in animal communication, issues relating to defining and classifying multimodal signals, and particular issues to consider with multimodal (as opposed to multicomponent unimodal) communication. We go on to discuss the current state of the field, and outline the contributions contained within the issue. We finish by discussing future avenues for research, in particular emphasizing that ‘multimodal’ is more than just ‘bimodal’, and that more integrative frameworks are needed that incorporate more elements of efficacy, such as receiver sensory ecology and the environment.

197 citations

Journal ArticleDOI
TL;DR: This review focuses on the recent advances in the understanding of prereceptor ligand metabolism, GR subtypes and GR polymorphisms, and the impact of tissue- and individual-specific diversity in the glucocorticoid pathway on human health and disease.
Abstract: Glucocorticoids exert a wide variety of physiological and pathological responses, most of which are mediated by the ubiquitously expressed glucocorticoid receptor (GR). The glucocorticoid response varies among individuals, as well as within tissues from the same individual, and this phenomenon can be partially explained through understanding the process of generating bioavailable ligand and the molecular heterogeneity of GR. This review focuses on the recent advances in our understanding of prereceptor ligand metabolism, GR subtypes and GR polymorphisms. Furthermore, we evaluate the impact of tissue- and individual-specific diversity in the glucocorticoid pathway on human health and disease.

197 citations