0000000000417076
AUTHOR
Johanna Honkavaara
Ultraviolet cues in fruit-frugivore interactions
All diurnal birds studied so far, many reptiles, amphibians, fish and some rodents are able to detect near-ultraviolet light (UV; 320-400 nm) invisible to humans. In many animals, UV cues have been found to play a role in foraging and mate choice. As many fruits reflect UV light, frugivores sensitive to UV may also use these cues in foraging. Fruit colours and their contrast with background coloration may attract frugivores. In this thesis, I studied the fruit colour preferences of both redwings (Turdus iliacus) and small rodents (house mice, Mus musculus and bank vole, Clethrionomys glareolus).
Fruit Colour Preferences of Redwings (Turdus iliacus): Experiments with Hand-Raised Juveniles and Wild-Caught Adults
Certain fruit colours and their contrast with the background coloration are suggested to attract frugivorous birds. To test the attractiveness of different colours, we performed three experiments in laboratory with controlled light conditions. In the first two experiments, we studied the fruit colour preferences of naive juvenile redwings. In the third experiment, we continued to investigate whether the contrast of the fruit colour with the background coloration affects the preference of both naive juveniles and experienced adult redwings. In the first experiment, juvenile birds preferred black, UV-blue and red berries, to white ones. In pairwise trials, a new set of juveniles still preferr…
Ultraviolet reflection and female mate choice in the pied flycatcher, Ficedula hypoleuca
In pied flycatchers females seem to prefer male territory quality rather than male characteristics, and the results of female mate choice experiments are divergent. In this outdoor aviary study, we examined how altering the ultraviolet reflection of males affects female mate choice behaviour. We chose pairs of males with similar human-visible dorsal colour and morphological traits. We then reduced the proportional ultraviolet reflectance in one male with sunscreen chemicals. The other male was treated with a chemical that slightly increased the ultraviolet reflectance of the plumage. In the experiment females clearly preferred males with slightly increased ultraviolet reflection. Our result…
Ultraviolet vision and foraging in terrestrial vertebrates
Tetrachromatic colour vision, based on four ‘main’ colours and their combinations, is probably the original colour vision in terrestrial vertebrates. In addition to human visible waveband of light (400–700 nm) and three main colours, it also includes the near ultraviolet part of light spectrum (320–400 nm). The ecological importance of ultraviolet (UV) vision in animals has mainly been studied in the context of intra- and inter-sexual signalling, but recently the importance of UV vision in foraging has received more attention. Foraging animals may use either UV cues (reflectance or absorbance) of food items or UV cues of the environment. So far, all diurnal birds studied (at least 35 specie…