National Repository of Grey Literature 133 records found  beginprevious72 - 81nextend  jump to record: Search took 0.01 seconds. 
Effects of melanin-based coloration and commensalism on performance in behavioural tests: a comparative study
Kahounová, Hana ; Frynta, Daniel (advisor) ; Šumbera, Radim (referee)
An intraspecific coat colour polymorphism exists in the genus Acomys. Some populations are dark and others are light-colored. Dark populations live in lava deserts, savannas and in the commensal habitat of Egypt. The subject of this thesis is to compare selected populations of Acomys in behavioral test of forced exploration. They are dark commensal, light secondary non-commensal, light non- commensal, and one dark non-commensal populations. The aim of this research is to find out whether the dark commensal populations of Acomys cahirinus differ in behavior from other populations and whether dark populations differ in behavior from light populations. According to the results, the observed behavioral parameters do not show significant differences between populations. The dark commensal populations of A. cahirinus did not differ significantly from other populations in exploratory behavior. But the dark populations preferred a dark background. No apparent differences in behavior between differently colored populations were found. However, the variability in tested behavior between populations was found. Key words: exploratory behavior, melanin, commensalism, comparative approach, open field test, Acomys
Hormonal control of sexually dimorphic traits in lizards
Schořálková, Tereza ; Kratochvíl, Lukáš (advisor) ; Reichard, Martin (referee) ; Frynta, Daniel (referee)
This Ph.D. thesis is fosuced on hormonal control of sexual dimorphism in lizards and is composed of four contributions. Sex steroid hormones are important for development and regulation of sexual dimorphism in reptiles, but particular traits are controlled by different endogenous mechanisms. Male sexual behaviour of the gecko E. macularius is controlled by testosterone and can be successfully induced in females, only the onset and cessation of the behaviour take longer than in males. The onset and cessation of particular traits are not immediate for both sexes, and this time component has to be taken into account in future experiments using hormonal manipulations. In other species of the gecko, P. picta, testosterone and dihydrotestosterone stimulates the expression of male sexual behaviour in females as well. Male offensive aggression occurs only in testosterone-treated females, probably due to its conversion to biologically active estradiol in the brain, testosterone thus stimulates offensive behaviour probably only indirectly. Both androgens also stimulate the growth of the male copulatory organs, hemipenes, in females, but in different way than the size of penis in male mammals. Sexual behaviour of both gecko species is associated with sex recognition, which is allowed by androgen-triggered cues in...
Acoustic communication of selected mammals and birds: identification of vocal categories and individuals
Policht, Richard ; Frynta, Daniel (advisor) ; Špinka, Marek (referee) ; Červený, Jaroslav (referee)
2 Summary Identification of vocal categories (e.g. call types, individuals, species) is a key task when we want to classify animal sounds. Same calls, especially broadband acoustic signals with varying frequency and amplitude modulation present problem for classification, because their energy is spread over a wide range of frequencies. In these sounds is difficult to decide which acoustical parameter to measure. To analyse complex vocalizations I applied a multiparametric method with using both temporal and spectral parameters. The most useful variables were variables describing distribution of the spectral energy. Frequency parameters were also useful in the case of tonal calls. I described vocal repertoire of Northern white rhinoceros and Bactrian camel. Both animals have low-frequency calls in their repertoire close to infrasound range, but it is evident that these signals are not used for long-distance communication. It seems that low-frequency components of their sounds are by product of their large body size. Growling sounds of camels are also interesting by their cohesive function, in contrast to growling sounds of rhinos and other mammals where such as calls are produced during aggressive interactions. I examined whether individual identity might be also encoded in very simple song types in...
Body size as an implicit factor: case studies of life-history strategies and behaviour
Šimková, Olga ; Frynta, Daniel (advisor) ; Sedláček, František (referee) ; Rehák, Ivan (referee)
Body size has a potential to influence almost any trait in animal biology. The thesis contains four case studies (I - IV) covering four various situations and four various taxa, mainly squamate reptiles (Lepidosauria). Body size is a connecting factor for all these studies, in which I and my co-authors tried to elucidate various implications of body size. I. The sex ratio in Cuban boa (Chilabothrus angulifer) litters is often male or female biased. The neonates are so large, that are able to accept the same type of prey as are adults (in contrast to the other Chilabothrus species). We found that both the sexes are of the same size and shape at birth. Large size of the neonates a long lifespan lead to considerable generation overlaps. This could clarify our findings that small females produce sons whereas the larger ones deliver daughters. Males are smaller than females, probably also less philopatric and refuse food during breeding season. We can conclude that females manipulate the sex ratio of neonates according to its own body size, in order to decrease the probability of competition with their own offspring. II. Mangrove-dwelling monitor lizard (Varanus indicus) shows one of the greatest degrees of sexual size dimorphism among monitor lizards. We recorded the growth of the individuals from...
Kin recognition in humans
Kapicová, Lucie ; Štěrbová, Zuzana (advisor) ; Frynta, Daniel (referee)
This work reviews various papers focused on human kin recognition. First, it briefly describes evolutionary reasons for kin recognition; then, it deals with issues regarding the terminology, and it continues with the introduction of recognition mechanisms (phenotype matching, recognition alleles, spatial distribution and association) and of modalities utilized for recognition (visual, olfactory, acoustic, and tactile modalities). This work also discusses the cultural aspects of kin recognition. Cultural aspects are often omitted by authors even though they play an important role in human kin recognition. This works links the cultural aspects of kin recognition with the biological ones.

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