Anthropogenic noise negatively affects wildlife in a wide range of taxonomic groups. Especially for birds, a substantial number of observational studies have now shown negative associations between... Show moreAnthropogenic noise negatively affects wildlife in a wide range of taxonomic groups. Especially for birds, a substantial number of observational studies have now shown negative associations between noise pollution and abundance and diversity along roadsides. Researchers investigating birds’ behavioural responses to high level noise to date have mostly focused on the immediate adjustment of vocal signalling behaviour. However, there is more than one mechanism by which birds might cope with increasing noise levels. They may show immediate behavioural reactions, such as spatial avoidance and/or vocal adjustment, but also more ontogenetic adjustments with long-term consequences like changes in sensory and personality traits. To test these potential effects of traffic noise on birds, I conducted a series of experiments using zebra finches. I have demonstrated that traffic noise per se can contribute to spatial avoidance in birds and cause variation in parental behaviour, and that there can be changes in noise avoidance behaviour in the course of a lifetime. These results provide new insights into the potential impacts of noise on birds. Show less
The effects of anthropogenic noise on interactions between predators and their prey are still little understood. This thesis aims to fill pressing knowledge gaps on this topic by studying how... Show moreThe effects of anthropogenic noise on interactions between predators and their prey are still little understood. This thesis aims to fill pressing knowledge gaps on this topic by studying how anthropogenic noise affected various stages in the prey-hunting of predators and the predator-avoidance of prey. For predators, I investigated whether an¬thropogenic noise could influence habitat choice (chapters 2 and 3), foraging efficiency (chapter 3) and communication between foraging group members (chapter 4). For prey, I studied how anthropogenic noise affected prey behaviour outside of predation con¬texts (chapter 5) and if current and previous vessel noise exposure affected anti-predator behaviour when a simulated predator attacked (chapter 6). The multi-disciplinary studies of this thesis combine to unravel more insight into the influence of noise on predator-prey relationships in the marine environment. Further investigations should focus on revealing the mechanistic underpinning of noise effects on behaviour of both predator and prey. Only then will we be able to reduce the impact of noise on marine ecosystems. Show less
Hubert, J.; Neo, Y.Y.; Winter, H.V.; Slabbekoorn, H. 2019
Anthropogenic sources increasingly contribute to the underwater soundscape and this may negatively impact aquatic life, including fish. Anthropogenic sound may mask relevant sound, alter behaviour,... Show moreAnthropogenic sources increasingly contribute to the underwater soundscape and this may negatively impact aquatic life, including fish. Anthropogenic sound may mask relevant sound, alter behaviour, physiology, and may lead to physical injury. Behavioural effect studies are often seen as critical to evaluate individual and population-level impact. However, behavioural responsiveness likely depends on context and characteristics of sound stimuli. We pose that ambient sound levels, signal-to-noise ratio (SNR), and pulse rate interval (PRI), could affect the behavioural response of fish. To study this, we experimentally exposed groups of tagged European seabass (Dicentrarchus labrax) to different impulsive sound treatments that varied in pulse level, elevated background level, SNR, and PRI. Upon sound exposure, the seabass increased their swimming depth. The variation in the increase in swimming depth could not be attributed to pulse level, background level, SNR or PRI. It may be that the current range of sound levels or PRIs was too narrow to find such effects. Show less
Hubert, J.; Campbell, J.A.; Beek, J.G. van der; Haan, M.F. den; Verhave, R.; Verkade, L.S.; Slabbekoorn, H.W. 2018
Aquatic animals live in an acoustic world, prone to pollution by globally increasing noise levels. Noisy human activities at sea have become widespread and continue day and night. The potential... Show moreAquatic animals live in an acoustic world, prone to pollution by globally increasing noise levels. Noisy human activities at sea have become widespread and continue day and night. The potential effects of this anthropogenic noise may be context-dependent and vary with the time of the day, depending on diel cycles in animal physiology and behaviour. Most studies to date have investigated behavioural changes within a single sound exposure session while the effects of, and habituation to, repeated exposures remain largely unknown. Here, we exposed groups of European seabass (Dicentrarchus labrax) in an outdoor pen to a series of eight repeated impulsive sound exposures over the course of two days at variable times of day/night. The baseline behaviour before sound exposure was different between day and night; with slower swimming and looser group cohesion observed at night. In response to sound exposures, groups increased their swimming speed, depth, and cohesion; with a greater effect during the night. Furthermore, groups also showed inter-trial habituation with respect to swimming depth. Our findings suggest that the impact of impulsive anthropogenic noise may be stronger at night than during the day for some fishes. Moreover, our results also suggest that habituation should be taken into account for sound impact assessments and potential mitigating measures. Show less
Fish live in a world that is not silent. In fact, fish hear low frequency sounds and may need them for navigation, predator-prey interactions and mate attraction. Due to their dependence on sounds... Show moreFish live in a world that is not silent. In fact, fish hear low frequency sounds and may need them for navigation, predator-prey interactions and mate attraction. Due to their dependence on sounds, fish may be particularly sensitive to changes in their acoustic world. Since the 1900s, the acoustic world of fish has been altered by a new prominent sound source: human activities. These activities generate a cacophony of high-intensity sounds. At close range, they may cause tissue damage and temporary hearing loss. At further distances, more moderate sounds may cause auditory masking, behavioural changes and reduced efficacy in foraging and avoiding predators. Assessing the severity of behavioural impacts of sounds is not straightforward and are often problematic.This thesis used European seabass to study behavioural effects of man-made sounds of different temporal structures. It also compared the effects of tank-based experiments with open-water experiments. Finally, this thesis studied the habituation of fish to sound exposure and how sound effects are influenced by various environmental factors. Show less
Shafiei Sabet, S; Dooren, D. van; Slabbekoorn, H. 2016
Aquatic and terrestrial habitats are heterogeneous by nature with respect to sound and light conditions. Fish may extract signals and exploit cues from both ambient modalities and they may also... Show moreAquatic and terrestrial habitats are heterogeneous by nature with respect to sound and light conditions. Fish may extract signals and exploit cues from both ambient modalities and they may also select their sound and light level of preference in free-ranging conditions. In recent decades, human activities in or near water have altered natural soundscapes and caused nocturnal light pollution to become more widespread. Artificial sound and light may cause anxiety, deterrence, disturbance or masking, but few studies have addressed in any detail how fishes respond to spatial variation in these two modalities. Here we investigated whether sound and light affected spatial distribution and swimming behavior of individual zebrafish that had a choice between two fish tanks: a treatment tank and a quiet and light escape tank. The treatments concerned a 2 × 2 design with noisy or quiet conditions and dim or bright light. Sound and light treatments did not induce spatial preferences for the treatment or escape tank, but caused various behavioral changes in both spatial distribution and swimming behavior within the treatment tank. Sound exposure led to more freezing and less time spent near the active speaker. Dim light conditions led to a lower number of crossings, more time spent in the upper layer and less time spent close to the tube for crossing. No interactions were found between sound and light conditions. This study highlights the potential relevance for studying multiple modalities when investigating fish behavior and further studies are needed to investigate whether similar patterns can be found for fish behavior in free-ranging conditions. Show less
The acoustic courtship display of a male and a female great tit show all the characteristics of a passionate dance. This thesis examines the impact of anthropogenic noise on the acoustic... Show moreThe acoustic courtship display of a male and a female great tit show all the characteristics of a passionate dance. This thesis examines the impact of anthropogenic noise on the acoustic communication between males and females and the relationship with reproduction. Show less
