She spends more time incubating the eggs, while he builds the nest — and sometimes steals nesting materials from neighbouring penguins. These are among the behaviours documented in a new study conducted at Schönbrunn Zoo in collaboration with the University of Vienna, examining how northern rockhopper penguins (Eudyptes moseleyi) divide breeding responsibilities.
The research provides one of the first detailed examinations of the species’ breeding behaviour under human care, revealing significant differences between males and females during egg incubation and nest construction.
Males build nests, steal materials and initiate fights
Researchers observed and filmed 13 northern rockhopper penguin pairs over three months during the 2024 breeding season. The recordings were subsequently reviewed and the behavioural data statistically analysed.
The findings showed that females spent a greater proportion of their time incubating eggs, while males devoted significantly more time to nest building and maintenance.
Nest construction also involved competitive behaviour. Males initiated physical confrontations more frequently and stole nesting materials from other penguins significantly more often than females.
“Females took on a greater share of egg incubation, while males invested significantly more time in nest building,” explains Lisa Macdonald, lead author of the study from the University of Vienna’s Department of Behavioural and Cognitive Biology.
Both parents share chick-warming duties
The differences observed during incubation did not necessarily continue after the eggs hatched.
Once chicks emerged, both males and females participated in keeping them warm, with no clear difference between the sexes detected for this behaviour.
The study also identified a relationship between hatching success and the amount of time partners spent near each other.
Pairs in which at least one chick hatched spent more time in close proximity than pairs that experienced no successful hatching.
However, this association does not establish whether spending more time together contributed to successful hatching or resulted from it.
“The results show that females and males take on different, complementary tasks during breeding. However, we cannot conclude from these findings whether pairs actually coordinate these activities,” Macdonald explains.
Studying an endangered species at Schönbrunn Zoo
The northern rockhopper penguin is classified as Endangered on the International Union for Conservation of Nature (IUCN) Red List.
The species inhabits islands in the South Atlantic, where its populations face threats including overfishing, pollution and climate change.
Since 2015, Schönbrunn Zoo has coordinated the European Ex situ Programme (EEP) for northern rockhopper penguins and maintained the international studbook. According to the zoo, it also houses the largest northern rockhopper penguin colony in any zoological institution worldwide.
Successful breeding under human care contributes to maintaining a managed reserve population while creating opportunities to study behaviours that would be difficult to document in the wild.
“In the wild, it would be almost impossible to collect such detailed data on individual pairs because of the species’ remote distribution and the large size of its colonies. The zoo’s success in breeding this species therefore gave us a fantastic opportunity to examine its breeding behaviour closely over an entire season,” says Rasmus Praefke, from the University of Vienna’s Department of Behavioural and Cognitive Biology, who also participated in the study.
Dr Stephan Hering-Hagenbeck, Director of Schönbrunn Zoo, emphasises the value of research conducted in zoological institutions.
“Scientifically managed zoos make an important contribution to research on threatened species. Studies like this help us better understand their biology and gain insights that can support the conservation of their wild counterparts.”
The findings provide new information about the reproductive behaviour of northern rockhopper penguins, highlighting how males and females contribute differently at various stages of breeding and offering a foundation for further research into interactions between breeding partners.
