Adélie Penguins Cope with Climate Change

Question

The following text is adapted from a news article from the National Science Foundation (NSF) website, posted on February 6, 2013.

1
For decades, David Ainley has studied Adélie penguins in Antarctica. Ainley says the birds appear to be coping in different ways in response to climate change. But there is one question that begs for an answer: What are their overall chances of survival?

2
In 2009, Ainley and his colleagues received an NSF grant to conduct research on how penguin individuals and populations cope with climate change. He especially wanted to know why some penguins succeed in coping with climate change while others do not. He wanted to find out what qualities successful birds have.

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Each year, the Adélie penguins of Ross Island return from wintering at sea on ice floes to large bird colonies where they build nests and breed. The transition from ice floes to bird colonies is always a risky undertaking because of the harsh environment and predators. Success during this transition for especially young penguins depends entirely upon the cooperation of both parents, for feeding and foraging. Adélie penguins must travel repeatedly from the colonies into the adjacent ocean to find food. This traveling can be tricky and dangerous.

The Yin and Yang of Sea Ice

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Adélie penguins exist only where there is sea ice, just as many song birds exist only where there are trees. The sea ice upon which Adélies depend is frozen ocean water. Sea ice forms, grows, and melts in the ocean depending on the season.

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Except when the wind blows sea ice away, these Antarctic seas are covered by ice floes (pack ice). It is in these ice-covered waters that Adélie penguins find the fish and krill that they eat. But sometimes there can be too much ice. Penguins are really great at swimming but are slow at walking. Areas of open water allow the penguins to be more efficient at foraging and bringing back food to their chicks. Not surprisingly, the Adélie colonies are highly sensitive to minor changes in the amount of sea ice. The amount of sea ice is itself responsive to changing climate.

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“When the cover on the ocean reaches around 70 percent ice and there’s only 30 percent water, conditions become more difficult for Adélies,” says Ainley. “Above that point, penguins begin to have problems with access to the sea and spend too much time walking. Around 20 percent ice cover is ideal for them.”

Figure 1 – Modeling based on penguin data shows that the percentage of sea ice has an effect on the efficiency of Adélie penguin foraging. This graph shows the modeled effect of sea ice concentration of total mass of food delivered, per parent. Maximum efficiency is reached at about 12% but doesn’t change for higher concentrations. Dotted lines indicate range of probable values. Graph modified from ballard and others 2010.
The Veritical axis shows total food delivered in killograms from 0 to 8 in increments of 2. The horizontal axis shows ice concentration by percentage from 0 to 20 in increments of 5. The top dotted line starts at about 5 kilograms at 0% ice and curves up gradually to a little over 6 kilograms at 12% and remains at a little over 6 kilograms to 17%. The bottom dotted line starts at about 4 kilograms at 0% ice and gradually curves up to about 5 kilograms at 12% and remains at about 5 kilograms to 17%. A dark line, in between the two dotted lines, starts at a little over 4 kilograms at 0% ice and gradually curves up to between 5 and 6 kilograms at 12% and remains at between 5 and 6 kilograms to 17%.

Super Penguins

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Ainley and his fellow researchers are trying to determine why some penguins are more successful than others. They discovered that only 20 percent of individuals are successful breeders every year. They dubbed this group of penguins “super breeders.” They believe that these penguins hold clues as to how the species will adapt to a changing ocean.

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“We’ve been studying the foraging behavior of these super breeders, comparing it to other penguins, and we found that the super breeders are kind of the Michael Phelps1 of the penguin world. Their foraging trips are shorter because they dive deeper, dive more rapidly with shorter rest periods at the surface, and ultimately bring back more food to their chicks,” Ainley said.

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The ocean-going skills of the penguins are important when it comes to finding prey and finding it quickly. The fish and krill that Adélie penguins pursue are often in just one school of fish, which they keep revisiting. If the penguins wait too long to catch their breath before diving again, their meal may have swum away or competitors may have eaten it. Then they must search for another school. This takes time and energy. If Adélie penguins are to be successful, efficient swimming and foraging skills are essential.

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Ainley and colleagues hope to determine how age, experience, and physiology affect the skill set of penguins in their pursuit of prey. Also, Ainley wants to know if experience or inheritance has critical bearing on the breeding success for these penguin athletes. The next steps in his research relate to a penguin’s breath-holding capabilities.

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Ainley hopes that by investigating the foraging capabilities of super breeders, we can understand how Adélie penguins will cope with climate change. Ultimately, the amount of sea ice dictates how the penguins respond. If the sea ice goes away entirely, the penguins will disappear. But more subtle changes before then are important. With the unstable environment in which they live, Adélie penguins are being tested.

1Michael Phelps: A retired American swimmer and the most decorated Olympian of all time, with a total of 22 medals. He competed at the 2004, 2008, and 2012 Olympic games.

Excerpt from "Adelie Penguins Cope With Climate Change: Facing the Future - It all Depends on Sea Ice" by David Ainley. In the public domain.

Multiple Choice Question
Which prediction about adaptation due to natural selection is best supported by information in the text?

A.
The foraging capabilities of individual Adélie penguins will improve over time.

B.
The percentage of “super breeders” in the Adélie penguin population will increase over time.

C.
The Adélie penguin population will eventually nest on sea ice so they don't have to travel as far to find food.

D.
The Adélie penguin population will eventually be able to survive without sea ice.

Answer 1

The prediction about adaptation due to natural selection that is best supported by information in the text is:

B. The percentage of “super breeders” in the Adélie penguin population will increase over time.

This option is supported by the research findings discussed in the text, particularly in sections 7 and 11 where it highlights the "super breeders" and their advantageous foraging behaviors. Since these more successful penguins are better adapted to find food efficiently in a changing environment, it suggests that traits associated with being a "super breeder" may be passed on, potentially increasing their percentage in the population over time. The other options (A, C, and D) are not as strongly supported by the text.