Eat prey, love: a peek at penguins in times of plenty
Three-year study provides major insights into how African penguins forage to feed their chicks
African penguins have helped researchers understand significantly more about marine conservation and the importance of fishery management – and all they had to do was eat.
The foraging efforts of adult penguins along with the condition of their chicks were monitored over the past three years to find out how the abundance of fish at a given time affects the feeding habits and conditions of these endangered birds.
Importantly, a rare three-year fishery closure around Robben Island allowed researchers to observe the natural relationship between these “predators” and their prey without much human interference affecting the results.
“[The fishing closure] created a unique opportunity to study how African penguins directly respond to natural changes in local abundance of their prey,” said Dr Kate Campbell, who led the research at the University of Cape Town as part of her PhD project.
“Understanding how African penguins forage to feed their chicks in their variable marine environment can help us identify conservation measures for these endangered populations.”
The closure area, which stretched 20km around Robben Island, also provided a designated range to track the fluctuating number of fish that were present in the area at a given time. Throughout the three years these values were estimated with 12 hydro-acoustic surveys, which produce soundwaves that bounce off the swim bladders of sardines and anchovies, the main prey for penguins.
GPS-temperature-depth loggers were then used to track adult penguins’ fishing behaviours for one trip per breeding season, and the diet of breeding adults and the body condition of chicks were also measured within the Robben Island colony.
With the absence of fishing swaying the findings, the results of the research were clear. The penguins’ foraging behaviour and offspring conditions were found to be directly linked to the local abundance of anchovies and sardines during those respective times.
When there were fewer fish, foraging time and energy for the adults increased while the body condition of the chicks became worse owing to the additional delay between meals. The scarcity of fish also led to some variation between how some penguins behaved.
“While some ‘superstar’ penguins find food easily, others are less successful,” said Dr Richard Sherley of the University of Exeter. “Once food gets harder to find, more individuals will start to struggle and work harder, but they will do so at different rates, increasing the variation we see in foraging effort.”
These findings will be crucial to identifying problems with penguin colonies down the road, especially if they involve overfishing.
“Since these short-term changes will likely have knock-on effects for chick survival and penguin population size, they could be used as powerful early warning signs to inform fisheries’ policies and marine conservation efforts,” said Campbell.
“Technological advances also means there’s exciting potential to better understand how these endangered penguins behave when prey resources are scarce.”The challenge becomes creating an environment where the health of the penguins and responsible fishing can coexist.Dr Sherley said: “Hopefully, in the future, we could aim to effectively balance fishery management with penguins’ needs, to reduce the impact on local economies while maximising the benefits to our oceans.”The findings, published today in the Journal of Applied Ecology, can be found here.