Research themes - Behavioural Biology
The themes of our daily research activities are largely determined by the ongoing 4-year projects of PhD-students and collaborating MSc-students, as well as by initiatives of staff members in developing novel themes for new grant applications. Currently we have four PhD-students working in our group, and there are several research lines that may soon lead to new PhD-projects. Below an overview of project descriptions associated with the complementary themes that we work on in our group and that are orchestrated by Prof. Carel ten Cate, Dr. Katharina Riebel, and Dr. Hans Slabbekoorn.
- 1. Assessing the linguistic abilities of a songbird: syntax detection and use in zebra finches (Taeniopygia guttata)
Caroline van Heijningen & Carel ten Cate
The faculty of language is a prominent feature differentiating humans from other animals. The uniqueness of the language faculty is highly dependent on whether research on the communication systems of other animals reveals similar principles and mechanisms. Features such as vocal learning and categorical perception that were once thought to be unique for human language, are also found in other animal species groups such as songbirds. This project focuses on another aspect thought to be uniquely human: the ability to use and detect different syntax rules. The nature and development of the song syntax in zebra finch song are studied and operant conditioning experiments are carried out to test zebra finches for the ability to detect and distinguish between different types of syntax.
- 2. Bird speech? On the production and perception of formants in bird vocalizations
Verena Ohms (ALW) & Carel ten Cate
Human speech and bird vocalization are communicative behaviors with striking similarities. Both humans and many birds produce exceptionally complex vocalizations that exhibit rapid variations in multiple acoustic parameters. A central role in the coding of linguistic meaning in speech is played by formants. Several findings indicate that formants have a role in bird vocal communication as well. Despite these intriguing indications, the mechanisms underlying formant production as well as perception are a poorly understood and neglected dimension in bird communication. This project addresses the production, perception and communicative significance of formants in bird vocalizations.
- 3. The early vocal development of songbirds and human infants
Sita ter Haar, Carel ten Cate, Claartje Levelt & Niels Schiller (Dept. of Linguistics)
Vocal learning in songbirds and human infants show many parallels. For instance, both humans and songbirds acquire language/birdsong from a tutor during a sensitive phase early in life. A predisposition for (species-specific) vocalizations had been suggested. It still remains unclear to what extent this learning is constrained by unlearned perceptual biases. In this project the role of these biases and the influence of vocal input are investigated. By performing similar experiments in zebra finches (Taeniopygia guttata) and human infants, the comparability between the two species in this aspect is studied.
- 4. Developmental influences on song preferences in female songbirds.
A special feature of the song signaling system is that the development of songs results from learning processes. At present, little is known on how early exposure to song influences female preferences in song birds and how it interacts with perceptual biases. This project aims at investigating this question in the zebra finch (Taenopygia guttata) by carefully controlling song input during development to test its influence on later preferences. These are tested by letting females choose their preferred songs in operant tasks.
- 5. Developmental influences on female preferences for a sexually selected, culturally transmitted trait (NWO)
Marie-Jeanne Holveck & Katharina Riebel
Songbirds are known for their extremely elaborate mating signals and extensive vocal learning abilities. The quality of male learned song if susceptible and adversely affected by poor early condition may provide an honest indicator of their developmental history to females. While evidence is accumulating that female song preference, like male song, also results from early social learning, the process of preference acquisition as well as its susceptibility to suboptimal early condition is poorly understood. This project investigates how early environmental and social experience influences subsequent female preference and mate choice in the zebra finch, Taenioygia guttata.
- 6. Habitat-dependent divergence in urban and forest populations of blackbirds (Turdus merula)
Erwin Ripmeester & Hans Slabbekoorn
Cities form a novel habitat type that is clearly distinct from natural habitat. Bird species living in both urban and natural habitat are an excellent model system to study the evolutionary consequences of divergent selection pressures. In this project we are investigating if there are habitat-dependent differences in song, morphology and blood parasite infection between blackbirds from cities and forests. Additionally, we are examining with molecular techniques whether such habitat-dependent differences have an effect on the gene flow between urban and forest populations.
- 7. Acoustic communication in a noisy world; experimental study on behavioural flexibility as key to urban success in great tits
Wouter Halfwerk (NWO) & Hans Slabbekoorn
Behavioural flexibility may play an important role in adaptation to novel environments.Urban areas are replacing natural habitats at a high rate all over the world and provide an ideal laboratory to study behavioural changes in response to new selection pressures. The great tit (Parus major) is an urban survivor that shifts its song upwards in urban areas with elevated levels of low-frequency traffic noise. In this project we will focus on the mechanisms underlying these behavioural changes by experimentally increasing noise levels in two colour-banded natural populations. We will examine variation in behavioural flexibility across individuals, seasons and generations and relate individual differences to long-term fitness data.
- 8. The role of sound in cichlid courtship behaviour and the disturbing impact of anthropogenic noise
The Lake Victoria cichlid species flock has developed in only a very short time to a very large number of species. Sexual selection is thought to have been a very important factor in the process of speciation. Research has mainly focused on mate preferences for visual signals, but here we investigate the potential impact on mate choice for sounds generated by male Pundamilia nyererei cichlids during courtship. Furthermore, we explore experimentally whether ambient light and noise conditions affect courtship motivation and strategies.
- 9. Developmental influences of artificially raised noise conditions on fish behaviour, hearing morphology, and brain physiology
Hans Slabbekoorn & Frans Witte
Human activities raise underwater noise conditions to artificially high levels in many natural places as well as in fish tanks for aquaculture. High and artificial noise levels may cause stress and especially affect development of fish larvae, which are typically unable to escape noisy conditions. We explore the impact of artificial noise conditions on body development and juvenile and adult behaviour for two fish species: one with specially evolved organs that improve hearing sensitivity: the zebrafish, Danio rerio, and one without such organs: the Lake Victoria cichlid, Haplochromis piceatus.