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Neophobia, neophilia, and dietary conservatism in birds
Beranová, Eliška ; Exnerová, Alice (advisor) ; Hotová Svádová, Kateřina (referee)
Birds` reactions towards novelty are demonstrated by two significant processes - neophobia and neophilia. These reactions often vary according to specific type of novel stimulus. Differences in levels of neophobia and neophilia enable birds to deal with potential costs and benefits arising from encountering a novel stimulus. Reactions towards novelty in birds may vary between different species as well as within them. In between species variability in levels of neophobia/neophilia may be related to dietary strategy and lifestyle. Differences in neophobia/neophilia of an individual bird may be related to sex, age, and personality. Long-term avoidance of novel food - dietary conservatism may follow the initial food neophobia. Again it varies a lot between species as well as within them. Key words: neophobia, neophilia, dietary conservatism, novel stimulus, novel object, novel food
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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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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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Effect of body-margin shape on detectability of cryptic prey
Machalková, Kateřina ; Exnerová, Alice (advisor) ; Hotová Svádová, Kateřina (referee)
5 Abstract Subject of many studies dealing with interactions of predator and prey is behaviour and reactions of those predators who distinguish their prey by visual signals. The aim of the study was to compare the detectability of prey with a simple or structured body-margin shape of cryptically coloured true bugs Dysodius crenulatus and Dysodius lunatus (Aradidae) using a different type of background (tree bark of Acer, Gleditschia and Tilia). Background photos were presented in black and white and colour. The test was performed on naive birds and on the wild-caught adults of the Great Tits (Parus major) and the Blue Tits (Cyanistes caeruleus). The experiment was performed in the experimental cage with one-sided mirror glass. The influence of the body-margin shape of the prey was evident for certain groups, but the effect was depending on the age and specie of the birds and the type of the background. Different times of the search for prey were encountered as it was more difficult for birds to search for structured body-margin shape and the birds found faster preys with simple ones. When searching on the colour background the Great Tits were faster than on black and white background. Naive birds of the Great Tits were in search of prey faster than adults and vice versa with the Blue Tits. A separate task...
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Experimental studies of Müllerian mimetic complexes
Jůnová, Lenka ; Exnerová, Alice (advisor) ; Hotová Svádová, Kateřina (referee)
Mimicry is one of strategies which provides protection for the prey from predator attack. There are several kinds of mimetic relationships, one of them is Müllerian mimicry, i.e. mutualistic relationship between two unpalatable prey species. If there are more animal species in this relationship, it is called Müllerian mimetic complex. Relationships in mimetic complexes are affected by many factors like defence level and aposematic signals resemblance of particular species, their different frequencies, alternative prey, prey community structure or predator species and their experience level. These factors determine whether the relationship of the species involved is mutualistic or parasitic. They also affect predators behaviour and their learning rate, memory and generalisation between mimetic species. Powered by TCPDF (www.tcpdf.org)
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Biological research in ultraviolet spectra: evolutionary and eto-ecological implications of UV reflectance in organisms
Pecháček, Pavel ; Kleisner, Karel (advisor) ; Hotová Svádová, Kateřina (referee)
Many species have surface patterns capable of reflecting ultraviolet light. The presence of UV reflecting markings on invertebrates (e.g. beetles, spiders, and butterflies) and many vertebrates has been proven by numerous studies. In my work, I lay a particular stress on Lepidoptera and, within the vertebrate taxon, on birds. The existence of UV reflecting surfaces on fish and reptiles and consequent questions are also mentioned. The aim of my work is to summarize all existing knowledge about UV reflectance, and to discuss its significance for subsequent research. My work also deals with the function of the UV textures, mainly in sexual selection, intra- and interspecies signaling and in foraging behaviour of the studied taxa. The last section touches those groups which do not reflect the ultraviolet light but are visually sensitive to it, e.g. certain kinds of zooplankton, amphibians and small mammals. The resulting summary shows a great significance of UV reflecting textures in various branches of biology and their importance in ecology and evolution of many species.
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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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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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