Passive acoustic monitoring of the endangered African Penguin (Spheniscus demersus) using autonomous recording units and ecoacoustic indices

Abstract

African Penguins Spheniscus demersus are endangered and declining seabirds which make extensive use of vocal signals for intra-specific vocal communication. Accordingly, passive acoustic monitoring tools could be developed as robust population monitoring methods that cause minimal disturbance to the birds. In this study, we collected soundscape recordings at the Stony Point penguin colony (Betty's Bay, South Africa) during the breeding season in 2019 to document the circadian rhythms of vocal activity of this species and to investigate whether the magnitude of variation of three different ecoacoustic indices correlates with the number of ecstatic and mutual display songs counted in recordings, which might inform on the breeding activity of the colony. Indeed, whereas ecstatic display songs are produced by males during intersexual competition and territorial defence, mutual display songs are given by parents returning to the nest after foraging trips. We found that the vast majority of the display songs (> 80%) occurred between 04:00-08:00 and 17:30-21:30 h. We also found that the Acoustic Entropy Index was a good predictor of the number of penguins' songs within a recording. Overall, our study shows that African Penguins vocalizations have the potential to assist the monitoring of this species while minimizing disturbance.

Acoustic recording complements camera traps for monitoring sensitive penguin populations

“…2009) and reflect the findings of Favaro et al . (2021) for African Penguins. Arrival and departure times often vary between colonies (Boersma et al .…”

“…2014, Favaro et al . 2021). While much work remains to refine this method, our work has integrated acoustic recordings, camera trap data and in situ counts of nests or penguins to reveal relationships between acoustic metrics and local, short‐term penguin presence, as well as longer‐term density over larger spatial extents.…”

“…These bands were chosen to maximally isolate the sounds of adult penguins relative to other sounds in the soundscapes (Favaro et al . 2021). We then examined the dimensionality of each set of metrics using inter‐metric correlations and principal components analysis.…”

“…2019), only one study on African Penguins Spheniscus demersus has begun to consider the application of passive acoustics to penguin population monitoring (Favaro et al . 2021).…”

“…PAM can also provide additional insights into behavioural dynamics compared with other remote sensing techniques due to its much higher temporal resolution (Gasc et al 2017). To enhance monitoring of the spatial and temporal dynamics of seabird populations, PAM represents a potentially powerful tool in need of further testing (Borker et al 2019, Orben et al 2019, Favaro et al 2021.…”