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Factors affecting predators' search for cryptic prey
Kuncová, Aneta ; Exnerová, Alice (advisor) ; Hotová Svádová, Kateřina (referee)
This thesis is focused on selected mechanisms, which affect predators' search for cryptic prey. The purpose was to compare information concerning existence, content, duration and circumstances related to formation of a visual search image and it's existence in relation to other sensual modalities. The search image research was carried on many animal species, both invertebrates and vertebrates, with most experiments being carried on birds, specifically blue jays (Cyanocitta cristata) and pidgeons (Columba livia). There are many alternative explanations for the results of those experiments, either negating the search image's existence or just adding to it. The majority of studies agrees upon the existence of search image, but the circumstances of it's formation, as well as its duration and content are specific both for different kinds of predators (depending on their foraging strategies) and different kinds of prey. The differences can also be found in the search image's duration, depending on 5 predator's foraging strategy and encounter frequency with target prey. A decrease in this frequency results in disappearance of search image for the given prey. The experiments also show that the information content concerning the searched target, an essential part of the search image, depends on the prey's...
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Mirror-induced behaviour in animals
Forštová, Tereza ; Exnerová, Alice (advisor) ; Landová, Eva (referee)
The topic of self-awareness and mirror self-recognition has been more discussed since 1970, when the new procedure named mark test showed the self-recognition in chimpanzees. Although the theory that mirror self-recognition provides evidence of self-awareness is generally accepted, it was showed in the recent studies that it is not necessarily always true, and that the transition between "having self-awareness" and "not having self-awareness" is gradual. There are more mirror tests dealing with mirror self-recognition in animals, such as mirror-mediated spatial location task. Almost all tested species passed well this kind of mirror tests and showed that there was a certain degree of mirror-image understanding. However not all of them show mirror induced self-recognition. There are several reasons of negative results of mark test such as improper methods and procedures applied to particular species, as well as individual differences, e.g. in social isolation and previous experience with mirror. Problems appear in comparative testing of species with different body morphology, e.g. cetaceans, birds, and fish which have forelimbs in form of wings and fins. They are not able to show the same behavioral responses as primates, for which the original mark test was developed. Applied methods should be always...
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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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Factors affecting formation and persistence of dietary aversions
Křístková, Barbora ; Exnerová, Alice (advisor) ; Frynta, Daniel (referee)
Taste aversion conditioning is a specific type of associative learning. Long delay between conditioned and unconditioned stimulus is the main difference from classical learning. Trace conditioning is the most common type of conditioning, used in this type of learning. Conditioned stimulus is followed by unconditioned stimulus. Taste aversion is usually formed after one trial conditioning. Unconditioned stimulus may be nausea caused by a variety of chemicals. As an unconditioned stimulus may also be used nausea caused by radiation, forced or voluntary movement, rotation, ... The most commonly used unconditioned stimulus is lithium chloride. Food aversion was demonstrated in both invertebrates and vertebrates. Food aversion has not been demonstrated in amphibians.
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Mimetic complex of Central European red-and-black bugs (Heteroptera)
Hotová Svádová, Kateřina ; Exnerová, Alice (advisor) ; Žďárek, Jan (referee) ; Krištín, Anton (referee)
Aposematic animals signal to the predators their unprofitability (e.g. unpalatability, toxicity) Predators have either innate bias against warning signals or they have to learn to avoid aposematic prey. Aposematic species with similar warning signals profit from their resemblance and form mimetic complexes. Theoretically, there are five types of mimetic relations between species within the mimetic complex: Batesian, quasi-Batesian, quasi- Müllerian, Müllerian and super-Müllerian. Classification of mimetic relations depends on the level of mutual resemblance, and presence, type and efficiency of defensive mechanisms. Central European red-and-black true bugs (Heteroptera) were used as a model of mimetic complex in my Ph.D. thesis. We used six species of passerine birds. The species differ in body size, preferred food and reactions toward aposematic red-and-black prey and non- aposematic brown-painted prey. Although the diet of some passerine birds may include true bugs, there is evidence that birds mostly avoid aposematic species. In the first paper included in the thesis, we found that mimetic complexes may be predator dependent. There are differences in the extent of Batesian-Müllerian mimetic complexes and in the relations among the species involved. In the second paper, we analysed reactions of...
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Effects of pattern, size and background contrast of prey on discrimination learning in avian predators
Kuncová, Aneta ; Exnerová, Alice (advisor) ; Komárek, Stanislav (referee)
The topic of this master thesis was the effects of pattern, size and background contrast of prey on discrimination learning of avian predators. The aim of this study was to investigate the influence of selected components of warning coloration on aversive discrimination learning of avian predators of different age and sex. The choosen model organism was the Great tit (Parus major). The comparision was done between hand-reared naïve birds and wild-caught adults of different age and sex. The experiment was taking place in the experimental cage with one way mirror. The experiment used a design of simultaneous task with two pray which differed in one component of the coloration (pattern, size and background kontrast). The differencies in the ability of discrimination learning was found just between hand-rared naïve birds and wild-caught adults. Better results were shown by the wild-caught adults. The ability of discrimination learning of wild-caught adults was not influenced by the age and sex. Pattern was the only significant component of the warning coloration due to which the birds were able to memorise the discrimination task. Key words: avoidance learning, unpalatable prey, pattern, size, background, contrast
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Evolution and function of imperfect mimics in Müllerian and Batesian complexes
Kyselová, Daniela ; Exnerová, Alice (advisor) ; Tureček, Petr (referee)
Mimicry is an imitation of another species signal that means an evolutionary advantage to the mimicking species. Therefore, it would be expected for mimicry to be selected for high accuracy and mimics to closely resemble their models. However, many mimetic species resemble their models only imperfectly, and several hypotheses have been formulated to explain the existence of such inaccurate mimics. These hypotheses are not necessarily exclusive, and the explanation of imperfection might vary among different mimetic complexes. In this text, various mechanisms are discussed that may allow the evolution and maintenance of imperfect mimicry in different mimetic complexes. Attention is also paid to the role of predators' perception and behaviour in mimetic accuracy, as well as the trade-offs between mimicry and some opposing selection pressures, such as sexual selection. Keywords: imperfect mimicry, inaccurate mimicry, evolution of mimicry, predator perception, predator behaviour, predator learning
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Foraging and reproductive strategies of selected passerine birds
Kryštofková, Milena ; Exnerová, Alice (advisor) ; Sedláček, František (referee) ; Šálek, Miroslav (referee)
According to currently generally accepted model of evolutionary optimalization of parental investments, parental behavior should be balanced to bring the highest benefits (maximal expected value of progeny) with the lowest costs invested. This necessity establishes the pressure, which forces the organisms to balance their life-history strategies according to the changing environment. More than one solution frequently exists, and it may be crucial, which one is chosen in a given circumstances. This Ph.D. thesis deals with three passerine species and investigates their foraging, reproductive and antipredatory strategies, in the framework of "costs and benefits" theory of parental decisions and also in association with the phenomenon of synurbization. The paper by Kryštofková et al. (2006) "Parental foraging strategies and feeding of nestlings in Common Redstart Phoenicurus phoenicurus" inquires whether such factors as age of nestlings, their number, or sex of parents have influence on parental feeding frequency and foraging strategies (parameters of hunting in space and time); the literary data are controversial, even for one and the same passerine species. The male uses passive foraging mode more than female and as the nestlings grow older, the proportion of passive foraging mode is increasing, while...
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