1
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Lawrence JP, Rojas B, Blanchette A, Saporito RA, Mappes J, Fouquet A, Noonan BP. Linking Predator Responses to Alkaloid Variability in Poison Frogs. J Chem Ecol 2023; 49:195-204. [PMID: 36854928 DOI: 10.1007/s10886-023-01412-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 02/11/2023] [Accepted: 02/15/2023] [Indexed: 03/02/2023]
Abstract
Many chemically-defended/aposematic species rely on diet for sequestering the toxins with which they defend themselves. This dietary acquisition can lead to variable chemical defenses across space, as the community composition of chemical sources is likely to vary across the range of (an aposematic) species. We characterized the alkaloid content of two populations of the Dyeing Poison Frog (Dendrobates tinctorius) in northeastern French Guiana. Additionally, we conducted unpalatability experiments with naive predators, Blue Tits (Cyanistes caeruleus), using whole-skin secretion cocktails to assess how a model predator would respond to the defense of individuals from each population. While there was some overlap between the two D. tinctorius populations in terms of alkaloid content, our analysis revealed that these two populations are markedly distinct in terms of overall alkaloid profiles. Predator responses to skin secretions differed between the populations. We identified 15 candidate alkaloids (including three previously undescribed) in seven classes that are correlated with predator response in one frog population. We describe alkaloid profile differences between populations for D. tinctorius and provide a novel method for assessing unpalatability of skin secretions and identifying which toxins may contribute to the predator response. In one population, our results suggest 15 alkaloids that are implicated in predator aversive response. This method is the first step in identifying the causal link between alkaloids and behavioral responses of predators, and thus makes sense of how varying alkaloid combinations are capable of eliciting consistent behavioral responses, and eventually driving evolutionary change in aposematic characters (or characteristics).
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Affiliation(s)
- J P Lawrence
- Department of Biology, University of Mississippi, University, MS, 38677, USA. .,Lyman Briggs College, Michigan State University, East Lansing, MI, 48825, USA.
| | - Bibiana Rojas
- Department of Biology and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.,Konrad Lorenz Institute of Ethology, Department of Interdisciplinary Life Sciences, University of Veterinary Medicine Vienna, Savoyenstraße 1, 1160, Vienna, Austria
| | - Annelise Blanchette
- Department of Biology, John Carroll University, University Heights, OH, 44118, USA.,Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA, 70118, USA
| | - Ralph A Saporito
- Department of Biology, John Carroll University, University Heights, OH, 44118, USA
| | - Johanna Mappes
- Department of Biology and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.,Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, Helsinki University, Helsinki, Finland
| | - Antoine Fouquet
- Laboratoire Evolution et Diversité Biologique, UMR5174, Université Paul Sabatier, 31062, Toulouse Cedex 9, France
| | - Brice P Noonan
- Department of Biology, University of Mississippi, University, MS, 38677, USA
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2
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Winters AE, Chan W, White AM, van den Berg CP, Garson MJ, Cheney KL. Weapons or deterrents? Nudibranch molluscs use distinct ecological modes of chemical defence against predators. J Anim Ecol 2021; 91:831-844. [PMID: 34839542 DOI: 10.1111/1365-2656.13643] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/15/2021] [Indexed: 11/28/2022]
Abstract
Defensive chemicals are used by plants and animals to reduce the risk of predation through different mechanisms, including toxins that cause injury and harm (weapons) and unpalatable or odiferous compounds that prevent attacks (deterrents). However, whether effective defences are both toxins and deterrents, or work in just one modality is often unclear. In this study, our primary aim was to determine whether defensive compounds stored by nudibranch molluscs acted as weapons (in terms of being toxic), deterrents (in terms of being distasteful) or both. Our secondary aim was to investigate the response of different taxa to these defensive compounds. To do this, we identified secondary metabolites in 30 species of nudibranch molluscs and investigated their deterrent properties using antifeedant assays with three taxa: rock pool shrimp, Palaemon serenus, and two fish species: triggerfish Rhinecanthus aculeatus and toadfish Tetractenos hamiltoni. We compared these results to toxicity assays using brine shrimp Artemia sp. and previously published toxicity data with a damselfish Chromis viridis. Overall, we found no clear relationship between palatability and toxicity, but instead classified defensive compounds into the following categories: Class I & II-highly unpalatable and highly toxic; Class I-weakly unpalatable and highly toxic; Class II-highly unpalatable but weakly toxic; WR (weak response)-weakly unpalatable and weakly toxic. We also found eight extracts from six species that did not display activity in any assays indicating they may have very limited chemical defensive mechanisms (NR, no response). We found that the different classes of secondary metabolites were similarly unpalatable to fish and shrimp, except extracts from Phyllidiidae nudibranchs (isonitriles) that were highly unpalatable to shrimp but weakly unpalatable to fish. Our results pave the way towards better understanding how animal chemical defences work against a variety of predators. We highlight the need to disentangle weapons and deterrents in future work on anti-predator defences to better understand the foraging decisions faced by predators, the resultant selection pressures imposed on prey and the evolution of different anti-predator strategies.
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Affiliation(s)
- Anne E Winters
- School of Biological Sciences, The University of Queensland, Brisbane, Qld, Australia
| | - Weili Chan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld, Australia
| | - Andrew M White
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld, Australia
| | - Cedric P van den Berg
- School of Biological Sciences, The University of Queensland, Brisbane, Qld, Australia
| | - Mary J Garson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld, Australia
| | - Karen L Cheney
- School of Biological Sciences, The University of Queensland, Brisbane, Qld, Australia
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3
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Winters AE, Lommi J, Kirvesoja J, Nokelainen O, Mappes J. Multimodal Aposematic Defenses Through the Predation Sequence. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.657740] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Aposematic organisms warn predators of their unprofitability using a combination of defenses, including visual warning signals, startling sounds, noxious odors, or aversive tastes. Using multiple lines of defense can help prey avoid predators by stimulating multiple senses and/or by acting at different stages of predation. We tested the efficacy of three lines of defense (color, smell, taste) during the predation sequence of aposematic wood tiger moths (Arctia plantaginis) using blue tit (Cyanistes caeruleus) predators. Moths with two hindwing phenotypes (genotypes: WW/Wy = white, yy = yellow) were manipulated to have defense fluid with aversive smell (methoxypyrazines), body tissues with aversive taste (pyrrolizidine alkaloids) or both. In early predation stages, moth color and smell had additive effects on bird approach latency and dropping the prey, with the strongest effect for moths of the white morph with defense fluids. Pyrrolizidine alkaloid sequestration was detrimental in early attack stages, suggesting a trade-off between pyrrolizidine alkaloid sequestration and investment in other defenses. In addition, pyrrolizidine alkaloid taste alone did not deter bird predators. Birds could only effectively discriminate toxic moths from non-toxic moths when neck fluids containing methoxypyrazines were present, at which point they abandoned attack at the consumption stage. As a result, moths of the white morph with an aversive methoxypyrazine smell and moths in the treatment with both chemical defenses had the greatest chance of survival. We suggest that methoxypyrazines act as context setting signals for warning colors and as attention alerting or “go-slow” signals for distasteful toxins, thereby mediating the relationship between warning signal and toxicity. Furthermore, we found that moths that were heterozygous for hindwing coloration had more effective defense fluids compared to other genotypes in terms of delaying approach and reducing the latency to drop the moth, suggesting a genetic link between coloration and defense that could help to explain the color polymorphism. Conclusively, these results indicate that color, smell, and taste constitute a multimodal warning signal that impedes predator attack and improves prey survival. This work highlights the importance of understanding the separate roles of color, smell and taste through the predation sequence and also within-species variation in chemical defenses.
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4
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Caro T, Koneru M. Towards an ecology of protective coloration. Biol Rev Camb Philos Soc 2020; 96:611-641. [PMID: 33258554 DOI: 10.1111/brv.12670] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 11/05/2020] [Accepted: 11/09/2020] [Indexed: 12/15/2022]
Abstract
The strategies underlying different forms of protective coloration are well understood but little attention has been paid to the ecological, life-history and behavioural circumstances under which they evolve. While some comparative studies have investigated the ecological correlates of aposematism, and background matching, the latter particularly in mammals, few have examined the ecological correlates of other types of protective coloration. Here, we first outline which types of defensive coloration strategies may be exhibited by the same individual; concluding that many protective coloration mechanisms can be employed simultaneously, particularly in conjunction with background matching. Second, we review the ecological predictions that have been made for each sort of protective coloration mechanism before systematically surveying phylogenetically controlled comparative studies linking ecological and social variables to antipredator defences that involve coloration. We find that some a priori predictions based on small-scale empirical studies and logical arguments are indeed supported by comparative data, especially in relation to how illumination affects both background matching and self-shadow concealment through countershading; how body size is associated with countershading, motion dazzle, flash coloration and aposematism, although only in selected taxa; how immobility may promote background matching in ambush predators; and how mobility may facilitate motion dazzle. Examination of nearly 120 comparative tests reveals that many focus on ecological variables that have little to do with predictions derived from antipredator defence theory, and that broad-scale ecological studies of defence strategies that incorporate phylogenetics are still very much in their infancy. We close by making recommendations for future evolutionary ecological research.
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Affiliation(s)
- Tim Caro
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, U.K.,Center for Population Biology, University of California, Davis, CA, 95616, U.S.A
| | - Manisha Koneru
- Department of Evolution and Ecology, University of California, Davis, CA, 95616, U.S.A
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5
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Barnett CRA, Ringhofer M, Suzuki TN. Differences in predatory behavior among three bird species when attacking chemically defended and undefended prey. J ETHOL 2020. [DOI: 10.1007/s10164-020-00668-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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6
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Winsor AM, Ihle M, Taylor LA. Methods for independently manipulating palatability and color in small insect prey. PLoS One 2020; 15:e0231205. [PMID: 32255810 PMCID: PMC7138310 DOI: 10.1371/journal.pone.0231205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 03/18/2020] [Indexed: 12/04/2022] Open
Abstract
Understanding how the psychology of predators shapes the defenses of colorful aposematic prey has been a rich area of inquiry, with emphasis on hypothesis-driven experiments that independently manipulate color and palatability in prey to examine predator responses. Most of these studies focus on avian predators, despite calls to consider more taxonomically diverse predators. This taxonomic bias leaves gaps in our knowledge about the generalizability of current theory. Here we have adapted tools that have been successfully used with bird predators and scaled them down and tested them with smaller predators (Habronattus jumping spiders) and small insect prey (termites, milkweed bug nymphs, pinhead crickets, fruit flies). Specifically, we test (1) the application of denatonium benzoate (DB) to the surface of live termites, crickets, and fruit flies, and (2) the effectiveness of manipulating the palatability of milkweed bug nymphs through diet. We also test the effectiveness of combining these palatability manipulations with various color manipulations. Across several experiments, we confirm that our palatability manipulations are not detectable to the spiders before they attack (i.e., they do not produce aversive odors that spiders avoid), and show that unpalatable prey are indeed quickly rejected and spiders do not habituate to the taste with experience. We also investigate limitations of these techniques by assessing possible unintended effects on prey behavior and the risk of contact contamination when using DB-treated prey in experiments. While similar tools have been used to manipulate color and palatability with avian predators and relatively large insect prey, we show how these techniques can be effectively adapted for use with small invertebrate predators and prey.
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Affiliation(s)
- Alex M. Winsor
- Entomology and Nematology Department, University of Florida, Gainesville, FL, United States of America
- Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst, MA, United States of America
- * E-mail:
| | - Malika Ihle
- Entomology and Nematology Department, University of Florida, Gainesville, FL, United States of America
| | - Lisa A. Taylor
- Entomology and Nematology Department, University of Florida, Gainesville, FL, United States of America
- Florida Museum of Natural History, University of Florida, Gainesville, FL, United States of America
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7
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Hämäläinen L, Mappes J, Thorogood R, Valkonen JK, Karttunen K, Salmi T, Rowland HM. Predators’ consumption of unpalatable prey does not vary as a function of bitter taste perception. Behav Ecol 2019. [DOI: 10.1093/beheco/arz199] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Many prey species contain defensive chemicals that are described as tasting bitter. Bitter taste perception is, therefore, assumed to be important when predators are learning about prey defenses. However, it is not known how individuals differ in their response to bitter taste, and how this influences their foraging decisions. We conducted taste perception assays in which wild-caught great tits (Parus major) were given water with increasing concentrations of bitter-tasting chloroquine diphosphate until they showed an aversive response to bitter taste. This response threshold was found to vary considerably among individuals, ranging from chloroquine concentrations of 0.01 mmol/L to 8 mmol/L. We next investigated whether the response threshold influenced the consumption of defended prey during avoidance learning by presenting birds with novel palatable and defended prey in a random sequence until they refused to attack defended prey. We predicted that individuals with taste response thresholds at lower concentrations would consume fewer defended prey before rejecting them, but found that the response threshold had no effect on the birds’ foraging choices. Instead, willingness to consume defended prey was influenced by the birds’ body condition. This effect was age- and sex-dependent, with adult males attacking more of the defended prey when their body condition was poor, whereas body condition did not have an effect on the foraging choices of juveniles and females. Together, our results suggest that even though taste perception might be important for recognizing prey toxicity, other factors, such as predators’ energetic state, drive the decisions to consume chemically defended prey.
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Affiliation(s)
- Liisa Hämäläinen
- Department of Zoology, University of Cambridge, Cambridge, UK
- Department of Biological and Environmental Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Johanna Mappes
- Department of Biological and Environmental Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Rose Thorogood
- Department of Zoology, University of Cambridge, Cambridge, UK
- HiLIFE Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
- Research Programme in Organismal & Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Janne K Valkonen
- Department of Biological and Environmental Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Kaijamari Karttunen
- Department of Biological and Environmental Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Tuuli Salmi
- Department of Biological and Environmental Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Hannah M Rowland
- Department of Zoology, University of Cambridge, Cambridge, UK
- Institute of Zoology, Zoological Society of London, Regent’s Park, London, UK
- Max Planck Institute for Chemical Ecology, Jena, Germany
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8
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Is eliciting disgust responses from its predators beneficial for toxic prey? Anim Behav 2019. [DOI: 10.1016/j.anbehav.2019.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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9
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Cyriac VP, Kodandaramaiah U. Don’t waste your time: predators avoid prey with conspicuous colors that signal long handling time. Evol Ecol 2019. [DOI: 10.1007/s10682-019-09998-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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10
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Multiple modalities in insect warning displays have additive effects against wild avian predators. Behav Ecol Sociobiol 2019. [DOI: 10.1007/s00265-019-2643-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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11
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Doktorovová L, Exnerová A, Hotová Svádová K, Štys P, Adamová-Ježová D, Zverev V, Kozlov MV, Zvereva EL. Differential Bird Responses to Colour Morphs of an Aposematic Leaf Beetle may Affect Variation in Morph Frequencies in Polymorphic Prey Populations. Evol Biol 2018. [DOI: 10.1007/s11692-018-9465-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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12
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Briolat ES, Zagrobelny M, Olsen CE, Blount JD, Stevens M. No evidence of quantitative signal honesty across species of aposematic burnet moths (Lepidoptera: Zygaenidae). J Evol Biol 2018; 32:31-48. [PMID: 30317689 PMCID: PMC6378400 DOI: 10.1111/jeb.13389] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 10/03/2018] [Accepted: 10/09/2018] [Indexed: 11/30/2022]
Abstract
Many defended species use conspicuous visual warning signals to deter potential predators from attacking. Traditional theory holds that these signals should converge on similar forms, yet variation in visual traits and the levels of defensive chemicals is common, both within and between species. It is currently unclear how the strength of signals and potency of defences might be related: conflicting theories suggest that aposematic signals should be quantitatively honest, or, in contrast, that investment in one component should be prioritized over the other, while empirical tests have yielded contrasting results. Here, we advance this debate by examining the relationship between defensive chemicals and signal properties in a family of aposematic Lepidoptera, accounting for phylogenetic relationships and quantifying coloration from the perspective of relevant predators. We test for correlations between toxin levels and measures of wing colour across 14 species of day‐flying burnet and forester moths (Lepidoptera: Zygaenidae), protected by highly aversive cyanogenic glucosides, and find no clear evidence of quantitative signal honesty. Significant relationships between toxin levels and coloration vary between sexes and sampling years, and several trends run contrary to expectations for signal honesty. Although toxin concentration is positively correlated with increasing luminance contrast in forewing pattern in 1 year, higher toxin levels are also associated with paler and less chromatically salient markings, at least in females, in another year. Our study also serves to highlight important factors, including sex‐specific trends and seasonal variation, that should be accounted for in future work on signal honesty in aposematic species.
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Affiliation(s)
- Emmanuelle S Briolat
- Centre for Ecology & Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn, UK
| | - Mika Zagrobelny
- Plant Biochemistry Laboratory and Copenhagen Plant Science Centre, Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Carl E Olsen
- Plant Biochemistry Laboratory and Copenhagen Plant Science Centre, Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jonathan D Blount
- Centre for Ecology & Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn, UK
| | - Martin Stevens
- Centre for Ecology & Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn, UK
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13
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Newell Wohner PJ, Cooper RJ, Schweitzer SH, Greenberg RS. Rusty blackbird patch use during winter in suburban landscapes. J Wildl Manage 2018. [DOI: 10.1002/jwmg.21548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
| | - Robert J. Cooper
- Warnell School of Forestry and Natural ResourcesUniversity of GeorgiaAthensGA30602USA
| | - Sara H. Schweitzer
- Wildlife Diversity ProgramNorth Carolina Wildlife Resources Commission106 Ferret Run LaneNew BernNC28562USA
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14
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Burdfield-Steel E, Brain M, Rojas B, Mappes J. The price of safety: food deprivation in early life influences the efficacy of chemical defence in an aposematic moth. OIKOS 2018. [DOI: 10.1111/oik.05420] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Emily Burdfield-Steel
- Centre of Excellence in Biological Interactions, Dept of Biological and Environmental Science; PO Box 35 FI-40014 Univ. of Jyväskylä Finland
| | - Morgan Brain
- Centre of Excellence in Biological Interactions, Dept of Biological and Environmental Science; PO Box 35 FI-40014 Univ. of Jyväskylä Finland
| | - Bibiana Rojas
- Centre of Excellence in Biological Interactions, Dept of Biological and Environmental Science; PO Box 35 FI-40014 Univ. of Jyväskylä Finland
| | - Johanna Mappes
- Centre of Excellence in Biological Interactions, Dept of Biological and Environmental Science; PO Box 35 FI-40014 Univ. of Jyväskylä Finland
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15
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Briolat ES, Burdfield-Steel ER, Paul SC, Rönkä KH, Seymoure BM, Stankowich T, Stuckert AMM. Diversity in warning coloration: selective paradox or the norm? Biol Rev Camb Philos Soc 2018; 94:388-414. [PMID: 30152037 PMCID: PMC6446817 DOI: 10.1111/brv.12460] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 07/25/2018] [Accepted: 07/27/2018] [Indexed: 01/03/2023]
Abstract
Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency‐dependent learning. However, widespread variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: genetic mechanisms, differences among predators and predator behaviour, and alternative selection pressures upon the signal. The mechanisms producing warning coloration are also important. Detailed studies of the genetic basis of warning signals in some species, most notably Heliconius butterflies, are beginning to shed light on the genetic architecture facilitating or limiting key processes such as the evolution and maintenance of polymorphisms, hybridisation, and speciation. Work on predator behaviour is changing our perception of the predator community as a single homogenous selective agent, emphasising the dynamic nature of predator–prey interactions. Predator variability in a range of factors (e.g. perceptual abilities, tolerance to chemical defences, and individual motivation), suggests that the role of predators is more complicated than previously appreciated. With complex selection regimes at work, polytypisms and polymorphisms may even occur in Müllerian mimicry systems. Meanwhile, phenotypes are often multifunctional, and thus subject to additional biotic and abiotic selection pressures. Some of these selective pressures, primarily sexual selection and thermoregulation, have received considerable attention, while others, such as disease risk and parental effects, offer promising avenues to explore. As well as reviewing the existing evidence from both empirical studies and theoretical modelling, we highlight hypotheses that could benefit from further investigation in aposematic species. Finally by collating known instances of variation in warning signals, we provide a valuable resource for understanding the taxonomic spread of diversity in aposematic signalling and with which to direct future research. A greater appreciation of the extent of variation in aposematic species, and of the selective pressures and constraints which contribute to this once‐paradoxical phenomenon, yields a new perspective for the field of aposematic signalling.
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Affiliation(s)
- Emmanuelle S Briolat
- Centre for Ecology & Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, U.K
| | - Emily R Burdfield-Steel
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, 40014, Finland
| | - Sarah C Paul
- Centre for Ecology & Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, U.K.,Department of Chemical Ecology, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Katja H Rönkä
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, 40014, Finland.,Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, 00014, Finland
| | - Brett M Seymoure
- Department of Biology, Colorado State University, Fort Collins, CO 80525, U.S.A.,Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, CO 80525, U.S.A
| | - Theodore Stankowich
- Department of Biological Sciences, California State University, Long Beach, CA 90840, U.S.A
| | - Adam M M Stuckert
- Department of Biology, East Carolina University, 1000 E Fifth St, Greenville, NC 27858, U.S.A
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16
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Zvereva EL, Doktorovová L, Hotová Svádová K, Zverev V, Štys P, Adamová-Ježová D, Kozlov MV, Exnerová A. Defence strategies of Chrysomela lapponica (Coleoptera: Chrysomelidae) larvae: relative efficacy of secreted and stored defences against insect and avian predators. Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/bly045] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
| | | | | | - Vitali Zverev
- Department of Biology, University of Turku, Turku, Finland
| | - Pavel Štys
- Department of Zoology, Charles University, Prague, Czech Republic
| | | | | | - Alice Exnerová
- Department of Zoology, Charles University, Prague, Czech Republic
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17
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18
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Hämäläinen L, Rowland HM, Mappes J, Thorogood R. Can video playback provide social information for foraging blue tits? PeerJ 2017; 5:e3062. [PMID: 28344901 PMCID: PMC5363260 DOI: 10.7717/peerj.3062] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 02/03/2017] [Indexed: 11/20/2022] Open
Abstract
Video playback is becoming a common method for manipulating social stimuli in experiments. Parid tits are one of the most commonly studied groups of wild birds. However, it is not yet clear if tits respond to video playback or how their behavioural responses should be measured. Behaviours may also differ depending on what they observe demonstrators encountering. Here we present blue tits (Cyanistes caeruleus) videos of demonstrators discovering palatable or aversive prey (injected with bitter-tasting Bitrex) from coloured feeding cups. First we quantify variation in demonstrators' responses to the prey items: aversive prey provoked high rates of beak wiping and head shaking. We then show that focal blue tits respond differently to the presence of a demonstrator on a video screen, depending on whether demonstrators discover palatable or aversive prey. Focal birds faced the video screen more during aversive prey presentations, and made more head turns. Regardless of prey type, focal birds also hopped more frequently during the presence of a demonstrator (compared to a control video of a different coloured feeding cup in an empty cage). Finally, we tested if demonstrators' behaviour affected focal birds' food preferences by giving individuals a choice to forage from the same cup as a demonstrator, or from the cup in the control video. We found that only half of the individuals made their choice in accordance to social information in the videos, i.e., their foraging choices were not different from random. Individuals that chose in accordance with a demonstrator, however, made their choice faster than individuals that chose an alternative cup. Together, our results suggest that video playback can provide social cues to blue tits, but individuals vary greatly in how they use this information in their foraging decisions.
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Affiliation(s)
- Liisa Hämäläinen
- Department of Zoology, University of Cambridge , Cambridge , United Kingdom
| | - Hannah M Rowland
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom; Institute of Zoology, Zoological Society of London, London, United Kindgom
| | - Johanna Mappes
- Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä , Jyväskylä , Finland
| | - Rose Thorogood
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom; Department of Biosciences, University of Helsinki, Helsinki, Finland
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Smith KE, Halpin CG, Rowe C. The benefits of being toxic to deter predators depends on prey body size. Behav Ecol 2016; 27:1650-1655. [PMID: 28028378 PMCID: PMC5181525 DOI: 10.1093/beheco/arw086] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 04/16/2016] [Accepted: 04/24/2016] [Indexed: 11/14/2022] Open
Abstract
Many prey have evolved toxins as a defense against predation. Those species that advertise their toxicity to would-be predators with conspicuous warning signals are known as "aposematic." Investment in toxicity by aposematically signaling prey is thought to underpin how aversive prey are to predators; increasing toxicity means that predators learn to avoid prey faster and attack them at lower rates. However, predators' foraging decisions on aposematic prey are determined not only by their toxicity, but also by their nutrient content: predators can trade-off the costs of ingesting toxin with the benefits of acquiring nutrients. Prey body size is a cue that positively correlates with nutrient content, and that varies within and between aposematic species. We predicted that a dose of quinine (known to be toxic to birds) would be a more effective deterrent to avian predators when prey were small compared with when they were large, and that the benefits of possessing toxin would be greater for small-bodied prey. Using an established laboratory protocol of European starlings (Sturnus vulgaris) foraging on mealworms (Tenebrio molitor), we found evidence for increased protection from a dose of quinine for small-bodied compared with large-bodied prey. This shows that larger prey need more toxin to attain the same level of defense as smaller prey, which has implications for the evolution of aposematism and mimicry.
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Affiliation(s)
- Karen E Smith
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place , Newcastle upon Tyne NE2 4HH , UK
| | - Christina G Halpin
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place , Newcastle upon Tyne NE2 4HH , UK
| | - Candy Rowe
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place , Newcastle upon Tyne NE2 4HH , UK
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20
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Halpin CG, Rowe C. The effect of distastefulness and conspicuous coloration on the post-attack rejection behaviour of predators and survival of prey. Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12887] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Christina G. Halpin
- Centre for Behaviour and Evolution; Newcastle University; Newcastle upon Tyne UK
| | - Candy Rowe
- Centre for Behaviour and Evolution; Newcastle University; Newcastle upon Tyne UK
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Newell Wohner PJ, Cooper RJ, Greenberg RS, Schweitzer SH. Weather affects diet composition of rusty blackbirds wintering in suburban landscapes. J Wildl Manage 2016. [DOI: 10.1002/jwmg.984] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Patti J. Newell Wohner
- Warnell School of Forestry and Natural Resources; University of Georgia; Athens GA 30602 USA
| | - Robert J. Cooper
- Warnell School of Forestry and Natural Resources; University of Georgia; Athens GA 30602 USA
| | - Russell S. Greenberg
- Smithsonian Migratory Bird Center; P.O. Box 37012-MRC 5503; Washington DC 20013 USA
| | - Sara H. Schweitzer
- Wildlife Diversity Program; North Carolina Wildlife Resources Commission; 102 Inge Court, New Bern, NC 28562 USA
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French A, Ali Agha M, Mitra A, Yanagawa A, Sellier MJ, Marion-Poll F. Drosophila Bitter Taste(s). Front Integr Neurosci 2015; 9:58. [PMID: 26635553 PMCID: PMC4658422 DOI: 10.3389/fnint.2015.00058] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 10/30/2015] [Indexed: 11/13/2022] Open
Abstract
Most animals possess taste receptors neurons detecting potentially noxious compounds. In humans, the ligands which activate these neurons define a sensory space called “bitter”. By extension, this term has been used in animals and insects to define molecules which induce aversive responses. In this review, based on our observations carried out in Drosophila, we examine how bitter compounds are detected and if bitter-sensitive neurons respond only to molecules bitter to humans. Like most animals, flies detect bitter chemicals through a specific population of taste neurons, distinct from those responding to sugars or to other modalities. Activating bitter-sensitive taste neurons induces aversive reactions and inhibits feeding. Bitter molecules also contribute to the suppression of sugar-neuron responses and can lead to a complete inhibition of the responses to sugar at the periphery. Since some bitter molecules activate bitter-sensitive neurons and some inhibit sugar detection, bitter molecules are represented by two sensory spaces which are only partially congruent. In addition to molecules which impact feeding, we recently discovered that the activation of bitter-sensitive neurons also induces grooming. Bitter-sensitive neurons of the wings and of the legs can sense chemicals from the gram negative bacteria, Escherichia coli, thus adding another biological function to these receptors. Bitter-sensitive neurons of the proboscis also respond to the inhibitory pheromone, 7-tricosene. Activating these neurons by bitter molecules in the context of sexual encounter inhibits courting and sexual reproduction, while activating these neurons with 7-tricosene in a feeding context will inhibit feeding. The picture that emerges from these observations is that the taste system is composed of detectors which monitor different “categories” of ligands, which facilitate or inhibit behaviors depending on the context (feeding, sexual reproduction, hygienic behavior), thus considerably extending the initial definition of “bitter” tasting.
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Affiliation(s)
- Alice French
- Evolution, Génomes, Comportement & Ecologie, CNRS, IRD, Université Paris-Sud, Université Paris-Saclay Gif-sur-Yvette, France
| | - Moutaz Ali Agha
- Evolution, Génomes, Comportement & Ecologie, CNRS, IRD, Université Paris-Sud, Université Paris-Saclay Gif-sur-Yvette, France
| | - Aniruddha Mitra
- Evolution, Génomes, Comportement & Ecologie, CNRS, IRD, Université Paris-Sud, Université Paris-Saclay Gif-sur-Yvette, France
| | - Aya Yanagawa
- Evolution, Génomes, Comportement & Ecologie, CNRS, IRD, Université Paris-Sud, Université Paris-Saclay Gif-sur-Yvette, France ; Research Institute for Sustainable Humanosphere, Kyoto University Uji City, Japan
| | - Marie-Jeanne Sellier
- Evolution, Génomes, Comportement & Ecologie, CNRS, IRD, Université Paris-Sud, Université Paris-Saclay Gif-sur-Yvette, France
| | - Frédéric Marion-Poll
- Evolution, Génomes, Comportement & Ecologie, CNRS, IRD, Université Paris-Sud, Université Paris-Saclay Gif-sur-Yvette, France ; AgroParisTech Paris, France
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Skelhorn J, Holmes GG, Hossie TJ, Sherratt TN. Multicomponent deceptive signals reduce the speed at which predators learn that prey are profitable. Behav Ecol 2015. [DOI: 10.1093/beheco/arv135] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Gregorovičová M, Černíková A. Reactions of leopard geckos (Eublepharis macularius) to defensive secretion of Graphosoma lineatum (Heteroptera Pentatomidae): an experimental approach. ETHOL ECOL EVOL 2015. [DOI: 10.1080/03949370.2015.1059895] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- M. Gregorovičová
- Department of Zoology, Faculty of Science, Charles University, Viničná 7, 128 44 Praha 2, Czech Republic
| | - A. Černíková
- Institute of Applied Mathematics and Information Technologies, Faculty of Science, Charles University, Albertov 6, 128 43 Praha 2, Czech Republic
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Barnett CA, Bateson M, Rowe C. Better the devil you know: avian predators find variation in prey toxicity aversive. Biol Lett 2015; 10:20140533. [PMID: 25392317 DOI: 10.1098/rsbl.2014.0533] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Toxic prey that signal their defences to predators using conspicuous warning signals are called 'aposematic'. Predators learn about the toxic content of aposematic prey and reduce their attacks on them. However, through regulating their toxin intake, predators will include aposematic prey in their diets when the benefits of gaining the nutrients they contain outweigh the costs of ingesting the prey's toxins. Predators face a problem when managing their toxin intake: prey sharing the same warning signal often vary in their toxicities. Given that predators should avoid uncertainty when managing their toxin intake, we tested whether European starlings (Sturnus vulgaris) preferred to eat fixed-defence prey (where all prey contained a 2% quinine solution) to mixed-defence prey (where half the prey contained a 4% quinine solution and the other half contained only water). Our results support the idea that predators should be more 'risk-averse' when foraging on variably defended prey and suggest that variation in toxicity levels could be a form of defence.
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Affiliation(s)
- Craig A Barnett
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Melissa Bateson
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Candy Rowe
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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Abstract
Aposematic prey advertise their toxicity to predators using conspicuous warning signals, which predators learn to use to reduce their intake of toxic prey. Like other types of prey, aposematic prey often differ in body size, both within and between species. Increasing body size can increase signal size, which make larger aposematic prey more detectable but also gives them a more effective and salient deterrent. However, increasing body size also increases the nutritional value of prey, and larger aposematic prey may make a more profitable meal to predators that are trading off the costs of eating toxins with the benefits of ingesting nutrients. We tested if body size, independent of signal size, affected predation of toxic prey as predators learn to reduce their attacks on them. European starlings (Sturnus vulgaris) learned to discriminate between defended (quinine-injected) and undefended (water-injected) mealworm prey (Tenebrio molitor) using visual signals. During this process, we found that birds attacked and ate more defended prey the larger they were. Body size does affect the probability that toxic prey are attacked and eaten, which has implications for the evolutionary dynamics of aposematism and mimicry (where species share the same warning pattern).
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Affiliation(s)
- Karen E Smith
- Centre for Behaviour & Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle, NE2 4HH, UK
| | - Christina G Halpin
- Centre for Behaviour & Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle, NE2 4HH, UK
| | - Candy Rowe
- Centre for Behaviour & Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle, NE2 4HH, UK.
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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.
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Affiliation(s)
- Christina G Halpin
- Centre for Behaviour and Evolution, Newcastle University, Newcastle upon Tyne, Tyne and Wear, UK
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Yoshimura Y, Kasuya E. Odorous and non-fatal skin secretion of adult wrinkled frog (Rana rugosa) is effective in avoiding predation by snakes. PLoS One 2013; 8:e81280. [PMID: 24278410 PMCID: PMC3836804 DOI: 10.1371/journal.pone.0081280] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Accepted: 10/18/2013] [Indexed: 11/21/2022] Open
Abstract
The roles played by nonfatal secretions of adult anurans in the avoidance of predation remain unknown. The adult Wrinkled frog (Rana rugosa) has warty skin with the odorous mucus secretion that is not fatal to the snake Elaphe quadrivirgata. We fed R. rugosa or Fejervarya limnocharis, which resembles R. rugosa in appearance and has mucus secretion, to snakes and compared the snakes’ responses to the frogs. Compared to F. limnocharis, R. rugosa was less frequently bitten or swallowed by snakes. The snakes that bit R. rugosa spat out the frogs and showed mouth opening (gaping) behavior, while the snakes that bit F. limnocharis did not show gaping behavior. We also compared the responses of the snakes to R. rugosa and F. limnocharis secretions. We coated palatable R. japonica with secretions from R. rugosa or F. limnocharis. The frogs coated by R. rugosa secretion were less frequently bitten or swallowed than those coated by F. limnocharis secretion. We concluded that compared to different frog species of similar sizes, the adult R. rugosa was less frequently preyed upon by, and that its skin secretion was effective in avoiding predation by snakes.
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Affiliation(s)
- Yuri Yoshimura
- Department of Biology, Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan
- * E-mail:
| | - Eiiti Kasuya
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan
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Chatelain M, Halpin C, Rowe C. Ambient temperature influences birds' decisions to eat toxic prey. Anim Behav 2013; 86:733-740. [PMID: 24109148 PMCID: PMC3791422 DOI: 10.1016/j.anbehav.2013.07.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/16/2013] [Accepted: 07/03/2013] [Indexed: 02/04/2023]
Abstract
Aposematic prey warn predators of their toxicity using conspicuous signals. However, predators regularly include aposematic prey in their diets, particularly when they are in a poor energetic state and in need of nutrients. We investigated whether or not an environmental factor, ambient temperature, could change the energetic state of predators and lead to an increased intake of prey that they know to contain toxins. We found that European starlings, Sturnus vulgaris, increased their consumption of mealworm, Tenebrio molitor, prey containing quinine (a mild toxin) when the ambient temperature was reduced below their thermoneutral zone from 20 °C to 6 °C. The birds differed in their sensitivity to changes in ambient temperature, with heavier birds increasing the number of toxic prey they ate more rapidly with decreasing temperature compared to birds with lower body mass. This could have been the result of their requiring more nutrients at lower temperatures or being better able to detoxify quinine. Taken together, our results suggest 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. Our study also provides novel insights into what factors affect birds' decisions to eat toxic prey, and demonstrates that selection pressures acting on prey defences can vary with changing temperature across days, seasons, climes, and potentially in response to climate change. We investigated the effect of temperature on birds' decisions to eat toxic prey. As it got cooler, birds were more likely to eat prey containing toxins. Heavier birds were more sensitive to changes in temperature. Selection pressures on prey defences will change over days, seasons and climes.
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Affiliation(s)
- M. Chatelain
- Museum National d'Histoire Naturelle, Paris, France
| | - C.G. Halpin
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle, U.K
| | - C. Rowe
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle, U.K
- Correspondence: C. Rowe, Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle NE2 4HH, U.K.
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33
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Carroll J, Sherratt TN. A direct comparison of the effectiveness of two anti-predator strategies under field conditions. J Zool (1987) 2013. [DOI: 10.1111/jzo.12074] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- J. Carroll
- Department of Biology; Carleton University; Ottawa ON Canada
| | - T. N. Sherratt
- Department of Biology; Carleton University; Ottawa ON Canada
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Predators' decisions to eat defended prey depend on the size of undefended prey. Anim Behav 2013; 85:1315-1321. [PMID: 23814280 PMCID: PMC3693033 DOI: 10.1016/j.anbehav.2013.03.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 11/29/2012] [Accepted: 03/05/2013] [Indexed: 11/22/2022]
Abstract
Predators that have learned to associate warning coloration with toxicity often continue to include aposematic prey in their diet in order to gain the nutrients and energy that they contain. As body size is widely reported to correlate with energetic content, we predicted that prey size would affect predators' decisions to eat aposematic prey. We used a well-established system of wild-caught European starlings, Sturnus vulgaris, foraging on mealworms, Tenebrio molitor, to test how the size of undefended (water-injected) and defended (quinine-injected) prey, on different coloured backgrounds, affected birds' decisions to eat defended prey. We 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. Consequently, we found no evidence that the mass of the defended prey or the overall mass of prey ingested affected the amount of toxin that a predator was willing to ingest, and instead the mass of undefended prey eaten was more important. This is a surprising finding, challenging the assumptions of state-dependent models of aposematism and mimicry, and highlighting the need to understand better the mechanisms of predator decision making. In addition, the birds did not learn to discriminate visually between defended and undefended prey based on size, but only on the basis of colour. This suggests that colour signals may be more salient to predators than size differences, allowing Batesian mimics to benefit from aposematic models even when they differ in size.
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S. Jones R, C. Davis S, Speed MP. Defence Cheats Can Degrade Protection of Chemically Defended Prey. Ethology 2012. [DOI: 10.1111/eth.12036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rebecca S. Jones
- Department of Evolution, Ecology and Behaviour; Faculty of Health & Life Sciences; Institute of Integrative Biology; University of Liverpool; Liverpool; UK
| | - Sian C. Davis
- Department of Evolution, Ecology and Behaviour; Faculty of Health & Life Sciences; Institute of Integrative Biology; University of Liverpool; Liverpool; UK
| | - Michael P. Speed
- Department of Evolution, Ecology and Behaviour; Faculty of Health & Life Sciences; Institute of Integrative Biology; University of Liverpool; Liverpool; UK
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Skelhorn J, Rowe C. Birds learn to use distastefulness as a signal of toxicity. Proc Biol Sci 2010; 277:1729-34. [PMID: 20129989 DOI: 10.1098/rspb.2009.2092] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Aposematic prey advertise their toxicity using conspicuous visual signals that predators quickly learn to avoid. However, it is advantageous for predators not to simply avoid toxic prey, but to learn about the amount of toxin that prey contain, and include them in their diets when the nutritional gains are high relative to the costs of ingesting the toxin. Therefore, when foraging on a defended prey population where individuals vary in their toxin concentration, predators should learn to use cues which distinguish prey with different levels of toxicity in order to include less defended individuals in their diets. In this experiment, we found that European starlings (Sturnus vulgaris) could learn to use a bitter taste to predict the amount of toxin that individual prey contained, and use that information to preferentially ingest less toxic prey to maximize their nutrient intake relative to the amount of toxin ingested. Our results suggest that bitter tastes could evolve as reliable signals of toxicity, and can help to explain why many toxins taste bitter. They also highlight the need to develop new mathematical simulations of the evolution of prey defences which incorporate the adaptive decision-making processes underlying nutrient and toxin management.
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Affiliation(s)
- John Skelhorn
- Institute of Neuroscience, Newcastle University, Newcastle NE2 4HH, UK.
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