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Evolution and function of hidden anti-predator signals
Ziková, Magdaléna ; Exnerová, Alice (advisor) ; Pipek, Pavel (referee)
Hidden anti-predator signals (HAS) are hidden colour patterns in an otherwise cryptic prey; they are revealed upon encountering a predator. HAS include deimatic signals (DS) and flash signals (FS). DS are used when at risk of predation, typically after being discovered by a predator. Their position in the predation sequence (PS) differs by species. DS are often linked with deimatic behaviour, that boosts their efficiency. The use of DS in later stages of the PS occurs more often in defended prey, which may thus speed up predators' avoidance learning. In undefended prey, DS may trigger startle or fear responses, confusion or sensory overload in the predator, thereby pausing or stopping the attack. FS are exposed during the prey's escape, usually early in the PS before a predator detects the prey. This can cause a predator to form a wrong impression of the prey's appearance, making it harder to find. FS can also attract the predator's attention during pursuit, thus decreasing its chance of noticing an evasive manoeuvre. Dynamic FS, in which different colours alternate during movement, can make it hard to estimate the prey's position. The presence of both types of HAS is often linked with prey body size. The efficiency of FS is affected by the flight initiation distance. The efficiency of DS is related to...
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The occurrence and the function of eyespots in the vertebrate colouration
Helebrant, Václav ; Fuchs, Roman (advisor) ; Pipek, Pavel (referee)
Eyespots are a striking feature in the colouration of many animals. These are spots of a circular shape, which in their external appearance subjectively resemble the eyes of vertebrates. In invertebrates, they are found in insects, crustaceans and molluscs, while they are most widespread in butterflies. Within vertebrates, eyespots are most common in fish. Among amphibians, they are found in frogs, but their occurrence has not yet been mapped in detail. Eyespots occur rather rarely in reptiles and birds, and only remotely similar patterns can be found in mammals. Current research on the function of eyespots more or less reliably demonstrates that they play an important role in defense against predators or in communication within intraspecific interactions. The eyespots can fulfill the anti-predation function in two ways. According to the intimidation hypothesis, eyespots serve to prevent a predator from attacking. However, it is not yet entirely clear whether the spots frighten predators because of their similarity to the eyes of dangerous animals, or whether predators avoid the spots because of their conspicuousness and contrast with the surroundings. According to the deflection hypothesis, eyespots attract predators, but they direct the attack away from vital parts of the prey's body. In...
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The occurrence and the function of aggressive mimicry in the vertebrates
Sommerová, Tereza ; Fuchs, Roman (advisor) ; Pipek, Pavel (referee)
Aggressive mimicry is used by a predator or parasite to deceive a potential prey or host. This bachelor thesis briefly summarizes other similar definitions of this phenomenon a then focuses on the species,especially vertebrates, that are included under this category. The use of the aggressive mimicry by fish of the families Blenniidae, Serranidae, Antennariidae, Labridae a snakes of the families Viperidae, Elapidae a Colubridae is described in more detail. Key worlds: aggressive mimicry, Peckhamian mimicry, caudal luring, toe/pedal luring, lingual luring
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Mapping of distribution of red deer and sika deer hybrids in Czechia using audio recordings - citizen science project
Nečasová, Monika ; Pipek, Pavel (advisor) ; Červený, Jaroslav (referee)
In the Czech Republic, as in other parts of Europe (e.g., British Isles), the native European red deer (Cervus elaphus) has been hybridising with sika deer (C. nippon), which was introduced from East Asia. The hybrids are fertile, and, therefore, can backcross with their parental species and threaten their genetic integrity. Offsprings of such multiple crosses are very difficult to identify according to their morphological traits, while more reliable genetic methods are financially and logistically demanding. This work follows the study of Long et al. from 1998, which showed clear differences in vocalization between red deer, sika deer and the first generation of their hybrids, and thus suggested the third way how to identify hybrids - bioacoustic analysis. We decided to test this method in the Czech Republic in a citizen science project, the aim of which was to map the distribution of parent species and their hybrids using audiorecordings of rut vocalisation. To allow more detailed analysis, we also recorded our own recordings on a professional recording device with a directional microphone. In total, 451 recordings were collected, of which only 263 with a vocalization of 162 individuals were selected for further analysis. Recordings from previous studies from Ireland (Long et al. 1998; Wyman et...
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Timing of egg laying in obligate brood parasites
Studecký, Jan ; Šulc, Michal (advisor) ; Pipek, Pavel (referee)
Obligate brood parasitism has evolved in 109 bird species around the world, which is approximately 1 % of all bird species. This alternative reproductive strategy is associated with complex evolution of the relationships between parasite and host(s) which is responsible for many adaptations on both sides. One of the important adaptations is the timing of egg laying either within a season, time of a day, or nesting stage of an individual host pair. The speed of laying itself is also no less important adaptation. Because brood parasitism is present worldwide in many different bird orders and parasites use variable species as their hosts, this adaptation is expected to be variable as well. My thesis will review information about timing of egg laying in all main taxonomical groups of brood parasites and will compare this adaptation between specialists and generalists, between closely related parasites with different hosts or between sedentary and migratory parasitic species. The main focus is on the question of coevolution with the host in relation to different timing strategies and an attempt to explain the differences in these strategies. Keywords: birds, coevolution, brood parasitism, egg laying, timing
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Effect of chromatic component on function of antipredatory warning signals
Truhlářová, Marie ; Exnerová, Alice (advisor) ; Pipek, Pavel (referee)
Warning coloration is used by prey to signal its unprofitability to potential predators. Warning colours may have different effects on various cognitive processes of predators (innate avoidance, avoidance learning, memory and generalization). Typical colours regarded as aposematic are red, orange and yellow. Red colour is considered to be the most effective signal and has a significant effect on avoidance learning, memory and generalization. Orange also represents an effective warning signal, though it has been studied less. Yellow is effective aposematic stimulus but it has frequently been found less effective compared to red and orange. Warning functions of white, blue, violet and ultraviolet colours were studied less frequently and their role in aposematism is not yet clear. Iridescent coloration might also be an effective warning signal affecting avoidance learning, memory and generalization. In this thesis I present a summary of information with regard to different warning colours and their effect on cognitive processes of predators. Key words: aposematism, warning coloration, cognitive processes, red, orange, yellow, iridescence, avoidance learning, innate avoidance, memory, generalization
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Mapping of distribution of red deer and sika deer hybrids in Czechia using audio recordings - citizen science project
Nečasová, Monika ; Pipek, Pavel (advisor) ; Červený, Jaroslav (referee)
In the Czech Republic, as in other parts of Europe (e.g., British Isles), the native European red deer (Cervus elaphus) has been hybridising with sika deer (C. nippon), which was introduced from East Asia. The hybrids are fertile, and, therefore, can backcross with their parental species and threaten their genetic integrity. Offsprings of such multiple crosses are very difficult to identify according to their morphological traits, while more reliable genetic methods are financially and logistically demanding. This work follows the study of Long et al. from 1998, which showed clear differences in vocalization between red deer, sika deer and the first generation of their hybrids, and thus suggested the third way how to identify hybrids - bioacoustic analysis. We decided to test this method in the Czech Republic in a citizen science project, the aim of which was to map the distribution of parent species and their hybrids using audiorecordings of rut vocalisation. To allow more detailed analysis, we also recorded our own recordings on a professional recording device with a directional microphone. In total, 451 recordings were collected, of which only 263 with a vocalization of 162 individuals were selected for further analysis. Recordings from previous studies from Ireland (Long et al. 1998; Wyman et...
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Functions of myrmecomorphy in the arthropods and its occurrence and potential functions in true bugs
Hrebiková, Tereza ; Exnerová, Alice (advisor) ; Pipek, Pavel (referee)
Myrmecomorphy (ant mimicry) is structural and chromatic (sometimes also chemical and behavioural) resemblance to ants. Ant-mimicking species can be found in many arthropod taxa particularly in spiders and true bugs. Myrmecomorphy may serve several functions, protecting the mimics either from the ants themselves or from predators. Mechanisms of ant mimicry have been studied mostly in spiders and some insect taxa (e.g. beetles). In true bugs (Hemiptera: Heteroptera), ant mimicry exists in many species belonging to several families, and it is present in both larvae and adults. Notwithstanding its frequent occurrence, the literature about ant mimicry in true bugs is limited only to several incomplete lists of myrmecomorphic species, hypotheses on mimicry functions, and a few experimental studies. This thesis aims to review (1) experimental studies focused on function of ant mimicry in spiders and insects and (2) occurrence, form and potential function of ant mimicry in true bugs (Heteroptera). Key words: Myrmecomorphy, function, Arthropoda, spiders, insects, Heteroptera
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Antipredatory function of aggregations in aposematic prey
Mitlenerová, Barbora ; Exnerová, Alice (advisor) ; Pipek, Pavel (referee)
Aggregation is a very important strategy of many organisms. It occurs in both vertebrates and invertebrates. Besides other functions (foraging, thermoregulation, maintenance of humidity protection against dessication, epigamic, hibernation or aestivation), aggregation also carries out antipredatory function. Aggregation of animals may reduce the risk of attacks by predators and prey mortality. Reduction of the attack probability might be caused by the predator confusion effect, lower risk of prey detectability, dilution effect, more effective vigilance of aggregation members and increase of strength of the warning signal produced by aposematic prey. Experimental studies, focused on the role of aposematic coloration in antipredatory functions use usually birds as predators. There are many kinds of insects, such as true bugs or mealworms, or artificial prey used as a prey in the experiments. The combination of aposematic signals and gregariousness of prey might have a significant influence on both probability and frequency of predator attacks. The length of predator's hesitation before the attack and the attack intensity used on attack may differ according to the coloration and presentation (gregariousness) of the prey and therefore the chance of survival varies. Aggregation may also improve...
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