The project is divided into three research aims:
(1) Describe the vocal communication used by foraging African penguins
(2) Quantify the implementation of an acoustic foraging network
(3) Evaluate the potential impact of anthropogenic marine noise on foraging African penguins
To respond to Research Aim 1, African penguins were equipped with acoustic devices (hydrophones), accelerometers and time-depth recorders. A total of 29 individuals were equipped from 3 different colonies over 2 breeding seasons from 2021 to 2022. The acoustic analyses of sound recordings revealed that African penguins produce several types of vocalisations all along their foraging trip, in the early part of the trip when the penguins were commuting, as well as further away when they were actively searching for prey in between and within dive bouts.
To respond to Research Aim 2, acoustic propagation experiments were conducted to estimate the theoretical active space of the African penguin sea-surface vocalisations (i.e. the distance at which the vocalisations can propagate in their natural foraging environment). Results confirm the hypothesis that African penguins can use vocalisations to communicate over relatively long distances at sea (scale of 100s of meters).
Furthermore, acoustic playback experiments were conducted where sea-surface vocalisations were broadcasted at sea (from a boat) using a speaker towards free-ranging foraging penguins. The behavioural response of the penguins was recorded using a hand-held microphone (vocal responses) and a camera (heads looking up towards the speaker, approaches). Overall, penguins responded to the majority of the playback experiments, mostly vocally and sometimes approaching the boat. The results of these playback experiments confirm the hypothesis that African penguins use vocal communication to maintain contact at sea and to form groups with conspecifics when they are foraging.
To respond to Research Aim 3, acoustic playback experiments of boat noise have been conducted from the sea shore on African penguins. The reaction of penguins included opening eyes, standing up and turning the head towards the speaker. These observations confirm that penguins can hear and react to the noise emitted by boats, and that such human-made noise is likely to disturb their natural behaviour. Furthermore, underwater acoustic devices were deployed in the foraging range of African penguins in Algoa bay (South Africa), in order to record the ambient marine noise that penguins are exposed to in their foraging area.
