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Factors affecting prey detectability for visual predators
Machalková, Kateřina ; Exnerová, Alice (advisor) ; Javůrková, Veronika (referee)
The cryptic coloration is one of the main ways to protect prey before the visually directing predators. Most animals use two basic strategies of crypsis, background-matching and disruptive coloration. The aim of this thesis was to summarize and evaluate knowledge about different strategies of cryptic coloration. The study was mainly focused on the confrontation between insect prey and predator bird. Experimental studies are comparing the effectiveness of cryptic coloration of prey by a combination of background-matching and disruptive coloration with prey characteristics (inner pattern contrast, background contrast, shape and pattern distribution, symmetry) or background parameters (background complexity, multiple backgrounds, the distance between the prey and the predator) that affect detectability. The results of the study conclude that disruptive coloration pattern in cryptic prey has better effects than the strategy of background-matching. Prey characteristics can affect detectability, but the results of individual studies are not conclusive. Even the background parameters results were unambiguous, the highest efficiency for prey detection time was a combination of disruptive coloration and the background complexity. The issue of camouflage is so complex that the majority of studies do not have...
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Antipredatory function of multimodal warning signals
Bednářová, Hana ; Exnerová, Alice (advisor) ; Pecháček, Pavel (referee)
Many kinds of prey are defended against predator attacks by multimodal warning signals. Signalling is multimodal if it concerns more than one sensory modality, for example sight and simultaneously audition (visual and acoustic signalling) or sight and olfaction or taste (visual and chemical signalling). Those two mentioned modality combinations are used by prey most frequently and are able to protect it in two ways. It can be an effective protection against multiple predators or these modalities cooperate and enhance their impact on one single predator. Multimodal warning signals are able to enhance initial aversion in predators, it can also influence learning process and predator's memory.
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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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Reactions of the jumping spider Evarcha arcuata to aposematic true bugs
Raška, Jan ; Exnerová, Alice (advisor) ; Šobotník, Jan (referee)
Jan Raška: Reactions of the jumping spider Evarcha arcuata to aposematic true bugs Abstract: This paper studies the effect of qualities of a prey on predatory behaviour of Evarcha arcuata (Araneae: Salticidae). Naturally coloured aposematic larveae of Pyrrhocoris apterus have been compared to two types of prey: 1) to identically coloured but in defensive secretion different larvae of Scantius aegyptius, and 2) differently coloured larvae of white mutants of P. apterus. The defensive secretion of S. aegyptius has been found less effective in the first interaction with predator than that of P. apterus, however, after several trials the difference of reactions of the spider has not been noticeable. When changed the species of prey, E. arcuata has symmetrically and considerably generalised between the two species. Significant difference has been established in memory test - while P. apterus has been avoided even after one day, S. aegyptius has been attacked as thought the spiders were naive. The learning sequence has been similar in both colour forms of P. apterus; the generalisation of the two colours has been symetrical as well. Both colour forms succeeded in memory test (e.g. spiders have proven difference in comparison with the naive ones), however, white mutants have been successfully attacked...
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Personality and cognition in great tit (Parus major)
Šimánková, Hana ; Exnerová, Alice (advisor) ; Sedláček, František (referee)
Success of an individual in various cognitive tasks can be influenced by many factors. Among the significant ones, that were studied in relationship with cognitive abilities, are animal personality and age. Great tit personality types are evaluated from explorative behavior and reaction towards novel object. We recognize Fast explorers, which are more active but superficial explorers, and Slow explorers, which are cautious, slower but thorough. Fast individuals manipulate sooner with a new food and non food objects. Slow individuals return later to offered food after being disrupted and they have higher breath rate. Some studies have revealed that Fast and Slow personalities differed in their cognitive abilities, for example in spatial tasks, in associative learning, in discrimination tasks or memory tasks, but many of them focus on only one type of task. In order to test both personalities thoroughly we tried to select types of tasks that focused on various abilities - two diverse types of extractive tasks, positive and aversive discrimination task and avoidance learning with firebugs (Pyrrhocoris apterus) in young naïve birds. Birds were tested in three age categories: young naïve hand reared birds, one year olds and two years and older birds. Fast and Slow individuals differed in aversive...
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Reactions of bird predators on components of repellent secretion of Heteroptera
Malečková, Dana ; Exnerová, Alice (advisor) ; Sedláček, Ondřej (referee)
Aposematic species of true bugs (Heteroptera) have multimodal signalization, which warns potential predators. This signalization consists of optical (coloration), chemical (unpalatable or repugnant substance) and acoustic (stridulation) warning signals. The aim of this thesis was to test whether the selected chemical substances have antipredatory function towards avian predators. Antipredatory function is anticipated in the chemical substances that form the majority in secretion in many taxa of true bugs (aldehydes and tridecane). In experiments with wild-caught great tits (Parus major) and blue tits (Cyanistes caeruleus) we tested if chemical substances and age of birds have influence on the latency related to the first manipulation with the prey. It was found that both species of tits reacted aversively to the mixture of aldehydes (2-decenal, 2-octenal, 2-hexenal) and to the total secretion of metathoracic glands of Graphosoma lineatum, whereas the mixture of the aldehydes with tridecane did not have any effect. The effect of age was not significant. We also tested the influence of immediate experience with striated shieldbug Graphosoma lineatum on naive great tits and their reactions to the prey with olfactoric signal of the shieldbug. Additionally, we investigated whether tested chemicals cause...
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Antipredatory behaviour, sexual selection and reproductive success in domestic sparrow (Passer domesticus).
Klvaňová, Alena ; Exnerová, Alice (advisor) ; Mlíkovský, Jiří (referee) ; Procházka, Petr (referee)
Anti-predator behaviour, sexual selection and reproductive success in the House Sparrow Passer domesticus Alena Klvaňová Summary of the thesis Individual components of parental care are disproportionally distributed among the parents in the House Sparrow. While the female broods the nestlings more often and feeds them more frequently, the male defends the nest more intensely. In an experimental study the parents did not adjust their nest defence intensity to behaviour of their partners, nor to brood parameters. Only males tended to defend the sooner broods more intensely, which is in concordance with the "brood value hypothesis". Male contribution to nestling feeding affected their body mass. Male nest defence intensity increased with the size of their melanin ornament. Thus, we assume that the ornament could signal male investment in this component of parental care, while it does not correlate with feeding frequency and time spent by incubation. This output is probably caused by pleiotropic effect of genes regulating melanogenesis, affecting e. g. testosterone plasma level, which is associated with increased agression and lower intensity of other components of parental care as nestling provisioning or incubation. We have also aked the question whether the anti-predator strategy in House Sparrow is stable...
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Exploration, neophobia and dietary conservatism in tits (Paridae)
Beranová, Eliška ; Exnerová, Alice (advisor) ; Fučíková, Eva (referee)
Neophobia and exploratory behaviour are two processes applied in great measure in birds' reactions towards novel stimuli. The specific demonstration of these two processes may differ between different species of birds as well as within them. We compared neophobia and exploratory behaviour in two species of tits (Paridae). Adult Great tits (Parus major) and Blue tits (Cyanistes caeruleus) did not differ neither in exploring novel environment and novel object nor in neophobia towards novel object near food. We have found great differences between juveniles of these two species. Juvenile Blue tits were more neophobic towards both novel objects. Age, sex and personality affected some differences within tested species. We tested whether there exist any differences in reactions towards novel food between and within species. We used red painted mealworm (larvae of Tenebrio molitor), house cricket (Acheta domestica) and aposematic bug (Pyrrhocoris apterus) as novel food. Adult wild-caught tits with plentiful experience with various feeds did not differ in reaction towards these types of novel food. In contrast hand-reared juvenile tits differed quite a lot. Juvenile Blue tits were more neophobic than juvenile Great tits towards all three types of novel food. We found dieraty conservatism, phenomenon...
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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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