Behavioural and heart rate responses to stressors in two populations of Little Penguins that differ in levels of human disturbance and predation risk

Species that are constantly exposed to disturbances, such as human disturbance or non-lethal contacts with predators or conspecifics, can experience chronic stress. Within a species range, variation in the frequency and predictability of such disturbances can lead to population differences in stress responses. Here, we investigated the stress response of Little Penguins Eudyptula minor to an introduced predator and a conspecific at two South Australian colonies that differed in habitat, conspecific density, levels of human disturbance and predation risk (high, low). We used playback experiments of Cat Felis catus or Little Penguin calls and recorded the behaviour and physiological (heart rate) response of adults in relation to playback type (Cat, Penguin) as well as habitat characteristics (habitat type, nest type, nest visibility) and number of conspecifics present. Our results showed that individuals from the high-disturbance colony (also living in a mixed habitat with fewer neighbours) exhibited higher vigilance and heart rate responses than individuals from the low-disturbance colony (living in a closed habitat with a high number of neighbours). Our results highlight that guidelines for managing penguin species cannot be generalized across populations and need to be colony-specific.

Automated summary

This study investigated the stress response of Little Penguins to an introduced predator and conspecific in two different habitats in South Australia. The results showed that individuals from high-disturbance colonies exhibited higher vigilance and heart rate responses compared to low-disturbance colonies.