Article: Metapopulation Tracking Juvenile Penguins Reveals an Ecosystem-wide Ecological Trap. Sherley et al, 2017. Current Biology. http://dx.doi.org/10.1016/j.cub.2016.12.054
Happy feet…in Africa
Did you know there are penguins in Africa? There are! See figure 1 for cuteness overload. They’re called African penguins (scientific name Spheniscus demersus), and they live around the south-western coast of Africa, near what is called the Benguela Current. This current brings cold, nutrient-rich water up from the deeper parts of the ocean, supporting lots of productivity (growth of photosynthetic organisms) and marine life. The fish we find on pizza, such as anchovies and sardines, are also found here. The African penguins feed on these fish, and migrate along the coast by season to follow their fishy food source.
Unfortunately, overfishing and climate change have damaged the Benguela system, reducing the number of fish available for the penguins to eat. Changes in water temperature have caused the remaining fish to migrate further south and east from where they would typically be, away from the Benguela Current and from the young penguins who feed on them (see figure 2 for a graphic representation of this). The penguins are now on the Endangered Species List.
So we know that these penguin populations are suffering, but to help the penguins we need to know more. Scientists from the United Kingdom, South Africa, Namibia, America, and Australia teamed up to track juvenile (young) African penguins, and find out how they are responding to our changing world. This isn’t an easy task though. Marine life can be hard to keep track of – they’re always swimming away.
Who goes there?
So how do you track penguins when they’re not marching across the Antarctic tundra, but are swimming along the coast of Africa? Satellites.
Scientists tagged 54 young African penguins with Platform Terminal Transmitters – essentially a tracking device that tells satellites where the penguins are. These transmitters are used in all kinds of ecological studies, including sea turtle and polar bear studies, and for tracking things like ships and ocean currents. In this case, the transmitter equipped penguins were recorded to tell scientists where the penguins were in the winter, and where they migrated to feed in the spring and summer.
This was a study that involved more than just the penguins, though. Other biotic (living) and abiotic (non-living) environmental factors were tracked as well. Satellites measured the Sea Surface Temperature (SST) and the Chlorophyll A concentrations. Chlorophyll A is a molecule in plants and in phytoplankton (tiny marine plants) that enable them to do photosynthesis. Chlorophyll A and SST typically indicate which regions of the ocean are productive and likely have lots of fish living. Hydro-acoustic surveys – technology using sound in water – told researchers how many anchovies and sardines (pizza toppings and penguin food) were in the study areas.
The scientists then took all of this penguin tracking data, fish stock information, water condition information, and productivity data, and put it into a computer model. The model allowed the scientists to understand the penguins’ responses to their main food source moving to areas that didn’t match with the temperature and chlorophyll measurements.
Happy feet follow cooler waters
The researchers found that as winter ended, the young penguins migrated north, following cool waters. This strategy – using environmental cues like water temperature – has paid off for the penguins in the past. They were rewarded for their journey with anchovies and sardines (and bad breath) galore. Recently, climate change has caused these fish stocks to migrate further south, i.e. the opposite direction of the penguins. This is further aggravated by overfishing in the region, depleting these key fish. This mismatch between very productive areas and low fish populations in this area creates an ecological trap.
Without the small fish to feed on, the penguins are forced to eat jellyfish and gobies. Taste aside, these alternative food sources provide less energy for the penguins. This causes significantly lower penguin survival to adulthood: 50% fewer penguins make it to breeding age than if this ecosystem were pristine. This impacts the young penguins disproportionately more than the adult penguins, who are better hunters and learn to adapt their migratory patterns.
Why does this matter?
Apart from being adorable, why do we care about the fate of the African penguin? Economically, penguins and other large marine animals contribute to local economies by drawing tourism. Ecologically, these animals act as crucial controls on other animals’ population sizes. Long term, this stabilizes ecosystems. Importantly, these large animals are often indicators of ecosystem health as a whole, so a declining penguin population indicates a degraded ecosystem.
So how do we help?
The first step in fixing problems is identifying them. For the first time, Richard Sherley and a multinational team of scientists discovered that climate change and overfishing is harming the young penguins in coastal Africa. Fixing this problem seems overwhelming though.
One way to help their penguins and other animals is through Marine Protected Areas (MPAs), where human activities are limited. Currently, however, they often are not large enough to protect migratory animals or their food stocks (Figure 6). Additionally, climate change affects all areas, even government protected ones. As climate change puts more pressure on these already stressed ecosystems, protection must be implemented on larger scales.
Larger scale protection of marine life could include fishing management to prevent overfishing. For the penguins, hand-rearing and release programs and post-disaster rehab programs are helping our feathered friends. The African Penguin and Seabird Sanctuary was founded in 2015 to study and protect the seabirds. Efforts by these folks plus others (like the Southern African Foundation for the Conservation of Coastal Birds) have saved many penguins so far.
Also encouraging is evidence that some species are adapting climate related changes, including birds in Australia and Russia. Life is clever, and adaptation can occur so that species become used to the warmer world. Studies of our world done by caring scientists such as the researchers here will equip us with knowledge to fight the effects of climate change. Most importantly, people like you can help protect and conserve natural habitats through getting involved by volunteering, educating, and caring.
Want to learn more about the African penguin? Follow these links!
Ted talk on ‘The Great Penguin Rescue’:
Southern African Foundation for the Conservation of Coastal Birds (SANCCOB):
Marine protected areas (MPA) are protected areas water bodies that restrict human activity for a conservation purpose, typically to protect natural or cultural resources. (from wikipedia.org)
Phytoplankton are photosynthesizing small plants that live in water
Sea surface temperature (SST) is the water temperature close to the ocean’s surface (from wikipedia.org)