|
| |
|
|
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...
|
|
| |
|
| |
|
| |
|
|
Effects of colour, shape, and pattern contrast of prey on discrimination learning in avian predators
Kišelová, Martina ; Exnerová, Alice (advisor) ; Kleisner, Karel (referee)
Aposematism is a phenomenon in which noxious animals signal their unprofitability to predators by using conspicuous and contrasting visual signals. These visual signals are composed from several components, with the most important being bright colours and contrasting internal patterns. To compare the difficulty of several discriminative stimuli that consist with components of aposematic warning colouration in live animals, experiments were conducted with naive and adult Great Tits (Parus major). The Great Tits were presented with artificial prey, in the form of paper bugs, with the use of a sequential discrimination task; the bugs used differed in colour, shape or internal contrast. Each of the components were tested separately to ensure that the learned or unlearned discrimination task was dependant on the difficulty of the component. The results showed that the birds learned discrimination task when they could use colour or contrast as a cue but if the cue was shaped, they were not successful. These results support the hypothesis that the obvious discriminatory element was colour. Nevertheless, a surprising result emerged when using the discriminatory element of contrast as it was believed that birds are unable to learn the task if they can discriminate only by one contrast. This study not only...
|
|
|
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...
|
|
|
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...
|
|
|
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...
|
|
|
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...
|
guest ::
RSS feed.