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Bird Appearances and Similarities
Figura, Roman ; Komárek, Stanislav (advisor) ; Daněk, Tomáš (referee) ; Jaroš, Filip (referee)
The presented work deals with a striking, yet usually neglected phenomenon by researchers, the similarity between the forms of different (closely unrelated) bird taxa. It mainly concerns visual signs of the body surface, the work also deals with other signs, including behavioral ones. The thesis demonstrates that these are not a few curious similarities, but a truly robust phenomenon, which apparently cannot be fully explained from a unifying point of view. Only some characters, which the work deals with, help their bearers to crypsis, aposematism or mimesis. In many other cases, their function is unknown. They can carry different functions in the life of their bearers, but it is often not possible to determine a single cause of their occurrence. In terms of the information contained, the work belongs to the largest works dealing with this topic known to the author.
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Výstražná signalizace barevných forem slunéčka východního (\kur{Harmonia axyridis})
BOROVIČKA, Martin
The efficiency of the aposematic defenses (colouration and chemical defence) used by three rare colour forms of Harmonia axyridis were tested using in the wild caught great tits (Parus major) as predators. I predicted that visually orienting predator will pay more attention to the rare colour forms, as they are not familiar with them and need to generalize the learned aversion to some other ladybirds to these novel ones.
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Spiders as senders and receivers of antipredatory warning signals
Raška, Jan ; Exnerová, Alice (advisor) ; Korenko, Stanislav (referee) ; Krištín, Anton (referee)
The introductory part of this thesis sums up the state of knowledge on aposematism and mimicry, the effect of aposematic and mimetic signals on spider predators, and cases when spiders do not receive but send such signals. Attachments of the thesis include four original manuscripts. In the first study, we presented jumping spiders (Evarcha arcuata, Salticidae) with different colour forms (red-and-black, yellow-and-black, white-and-black) of the firebug (Pyrrhocoris apterus, Pyrrhocoridae). Our goal was to compare reactions of the spiders to various intensity of aposematic signalization, expecting red-and-black coloration to have the strongest effect. Aversive learning of all colour forms was equally effective, but generalization of the learned avoidance to other colour forms was more effective after switch from less (white-and-black, yellow-and-black) to more (red-and-black) conspicuously coloured prey. When tested the next day, avoidance of the white-and-black prey got mostly forgotten. In the second study, we assessed little studied sensitivity of spiders to smells of unpalatable prey. After jumping spiders learned to avoid firebugs, most of them avoided the firebug smell, showing their sensitivity not only to optical, but also to chemical part of signalization of the unpalatable prey. In the...
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Evolution and function of polymorphism in warningly coloured prey
Fárová, Monika ; Exnerová, Alice (advisor) ; Šulc, Michal (referee)
Polymorphism can be expected in warningly colored prey if the prey is protected from predation by nothing else but its coloration. On the contrary, in defended prey, polymorphism was only until recently considered a controversial phenomenon due to its longer and costly avoidance learning. Individual moprhs can vary in different components of warning coloration: color, pattern, melanization degree, and internal and external contrast of colour patterns. This makes it difficult for predators to learn and remember warning signals of defended prey and avoid it in the future. Predator selection pressures and mechanisms leading to polymorphism differ between defended and undefended prey. For undefended prey, it is a negative frequency-depended selection that supports rare morphs or the multiple models hypothesis for one mimetic species. For defended prey, the polymorphism can occur temporarily (i. e., be unstable) and it also can be allowed by spatial heterogeneity of morphs or, as for undefended prey, one species can mimic multiple models. Quasi-Batesian mimesis could also contribute to the existence of the polymorphism, due to mechanisms similar to those in unprotected prey. Apart from selection by predators, there are other factors, that contribute to the existence of polymorhism in prey warning...
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Factors affecting long-term memory of aposematic signals in avian predators
Skoumalová, Žaneta ; Exnerová, Alice (advisor) ; Sedláček, František (referee)
The ability to memorize and recognize edible prey from inedible prey is essential for an individuals survival. Many species use aposematic signals for their defense. These are most often represented by distinctive colors or contrast patterns. The aim of this study was to find out in which time the memory consolidation for aposematic pray is achieved and if color or pattern increase its memorability. The choosen model species was the Great tit (Parus major). The comparision was done between handreared naïve birds and wild-caught adults of different age and sex. During the discriminatory task of consolidation experiment, birds were simultaneously presented with palatable and unpalatable prey in the form of paper dummies of bugs, differing in color (red versus green). The birds were divided into three groups with a different interval (0, 1 or 3 hours) for consolidation. The results of consolidation test show that adult birds were more successfull in solving the task than juvenile birds. The only difference between the experimental groups was that the group with one-hour interval achieved better results than other groups. The effect of color of palatable and unpalatable prey on discrimination learning was also found only in adults. Memorability of warning signals was tested using paper bugs of...
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Effects of multimodal warning siglals of Tritomegas sexmaculatus on reactions of bird predators
Binderová, Jana ; Exnerová, Alice (advisor) ; Kleisner, Karel (referee)
Aposematic animals advertise their defensive mechanisms to potential predators using warning signals. Signalling through more than one sensory pathway is called multimodal warning display. Most experimental studies of aposematism have been focused on the effect of a particular warning signal rather than on importance of multimodal signalling. Focusing on the multimodal signalling of real prey is the best way how to understand its effect in nature. The present study is focused on comparing the effect of multimodal warning display of insect prey with its particular warning signals on two species of bird predators. Multimodal warning signalisation of the burrowing bug, Tritomegas sexmaculatus consists of visual (black and white coloration), chemical (odour, possibly taste) and acoustic (stridulation) signals. We compared reactions of wild-caught great tit (Parus major) and blue tit (Cyanistes caeruleus) to three types of bugs with different warning displays. The non-manipulated bugs displayed multimodally, the brown painted bugs had their warning coloration manipulated and the dealatized bugs couldn't emit acoustic signals. The wild-caught birds of both species avoided all types of bugs. In an experiment with naive hand reared great tits we compared their reactions to non-manipulated and dealatized bugs. Naive...
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Role of aldehydes in multimodal aposematic signallig of true bugs
Bednářová, Hana ; Exnerová, Alice (advisor) ; Sedláček, Ondřej (referee)
1 Abstract: Multimodal signaling is quite common in nature. Even if we focus only on signaling among prey and its predator, we can still find many examples of communication combining more than one modality (vision, hearing, smell, taste). This thesis is about multimodal warning visual and olfactory signaling between true bugs (Heteroptera) and their avian predators. Aldehydes are an important compound of repellent secretion of most true bug species. They are considered to have defence effects against predators. In our experiments, we tested the effect of aldehydes mixture on behaviour of predators - naive hand-reared and experienced wild-caught adult great tits (Parus major) - towards several kinds of prey - aposematic true bugs Pyrrhocoris apterus, nonaposematic true bugs Pyrrhocoris tibialis and red painted mealworms (Tenebrio molitor larvae). We were focusing on the effect of aldehydes on initial reaction, learning process and predator's memory. Aldehydes elicited innate wariness in naive hand- reared great tits towards aposematic P. apterus, but not towards P. tibialis. Therefore it seems possible, that aldehydes act as a signal of unpalatability for naive predators, but only in multimodal combination with visual warning signal. Similar effect of aldehydes was not found in experiments with wild-caught...
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Interspecific comparison of social learning of food aversions in tits
Mitlenerová, Barbora ; Exnerová, Alice (advisor) ; Sedláček, František (referee)
Social learning in animals is a frequently studied topic, including birds. Great tits belong to frequently tested passerine species in this context. For this experiment we have chosen another tit species as model birds - adult and juvenile blue tits (Cyanistes caeruleus) and coal tits (Periparus ater). We tested an effect of social information on discrimination learning between palatable and unpalatable prey. Red and green artificial prey items resembling shieldbugs with a mealworm glued underneath were offered to birds. One variant was palatable, the other was unpalatable, soaked in bitter substance. Experimental groups were allowed to observe a pretrained tutor of the same species choosing palatable prey variant and rejecting the unpalatable one. The birds were then subjected to an individual discrimination learning task with simultaneously offered palatable and unpalatable prey items. The control group was not allowed to observe tutor and learned only individually. On the following day, all birds participated in a memory test. We tested if social information has an influence on avoidance learning in juvenile and adult birds of both species. We found that both species of tits were similarly successful in discrimination learning and there was no difference in success in performance between adult...
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Mechanisms and effectiveness of antipredatory defences within red-and-black mimetic complex
Kotlíková, Lucie ; Exnerová, Alice (advisor) ; Baňař, Petr (referee)
Strikingly coloured species can form mimetic complexes. One of them is an extensive black-and-red mimetic complex in the Palearctic region. It consists of representatives across arthropod taxa with different levels of defense and investment in it. To describe individual mimetic relationships in this complex, it is necessary to know the effectiveness of these defense mechanisms against predators. Reactions of individual predators vary considerably. Differences in reactions primarily depend on the ability to perceive some components of defense, using sensory and cognitive abilities. Mechanisms and effectiveness of antipredatory defence are the subject of numerous studies, but there is still a lack of description of some mechanisms among many representatives forming this mimetic complex. For this reason, further studies are needed to allow the derivation of mimetic relationships prevailing in this mimetic complex in the future. Keywords: mimicry, aposematism, antipredatory defense, colouration, mimetic complex
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Factors influencing effectiveness of aposematic signals against avian predators
Kuklová, Lucia ; Exnerová, Alice (advisor) ; Krištín, Anton (referee) ; Sedláček, František (referee)
This thesis focuses on various factors affecting effectiveness of aposematic signals against avian predators. Adult, wild-caught as well as hand-reared juvenile great tits (Parus major) were used as predators in the experiments. The thesis consists of the following four studies. In the first study, we compared the reactions of great tits from two geographically distant populations toward aposematic firebugs (Pyrrhocoris apterus) and their non-aposematic artificially made colour variant. The birds from the Bohemian population mostly avoided aposematic firebugs and attacked non-aposematic variant. Finnish birds, which lacked experience with firebugs from their natural environment, were less hesitant to attack both firebug colour forms. Although the Bohemian birds avoided the aposematic prey variant, they were not more neophobic than Finnish birds. We conclude that the geographic differences in reactions of the birds to aposematic prey can be explained by a different population-specific experience of the birds with local aposematic prey communities. In the second study, we compared effectiveness of two chemical defence strategies in leaf beetle larvae (Chrysomela lapponica) against great tits. The birds avoided larvae devoid of external secretions after the first attack, which indicates the presence...
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