African penguins' behaviour is affected by motor boat airborne noise: an experimental study on wild penguins

Data from: African penguins' behaviour is affected by motor boat airborne noise: an experimental study on wild penguins. Article published in Science of the Total Environment. Abstract Maritime traffic has expanded exponentially in recent decades, leading to a significant increase in marine noise pollution, a recognized threat to biodiversity. The African penguin (Spheniscus demersus), now classified as Critically Endangered, has experienced a dramatic population decline, with fewer than 8,000 breeding pairs remaining as of 2025. Among the drivers of this decline, noise pollution is suspected to have played an important role, especially near breeding colonies. This study experimentally assessed the impact of motor boat airborne noise on the behaviour of African penguins at the Stony Point colony (South Africa). Playback experiments conducted on land near their colony exposed groups of penguins to three noise levels (low: 61-64 dB, medium: 67-70 dB, high: 73-76 dB re 20µPa), simulating boats at varying distances. Results showed that all individuals reacted to the noise, primarily through increased vigilance at the expense of resting behaviours such as preening or standing. Individuals exposed to higher noise level showed stronger reaction to noise, including leaving the group. Although our experiments clearly under-estimated the full impact of marine noise pollution due to boat traffic (short duration of noise exposure, only airborne component of motor boat noise), our results show that noise exposure significantly altered the activity budget of this species, with potential physiological consequences. This study confirms experimentally the sensitivity of African penguins to airborne anthropogenic noise. These results emphasize the need to consider the implementation of noise mitigation measures into conservation plans for this species (e.g. limiting maritime traffic and boat speeds). The findings also suggest that noise impacts to the levels the birds were exposed to in this study can be temporary, offering an opportunity for rapid and effective conservation actions. Underlying data Data file 01. "DataTable_analysis1.csv" (analysis 1: avoidance of the noise). Data file 02. "DataTable_analysis2.csv" (analysis 2: behavioural response to noise). Data file 03. "DataTable_analysis3.csv" (analysis 3: modification of the behaviour during and following noise exposure).