Wednesday, November 30, 2016

Making a More Perfect Penguin

As a population, Magellanic penguins show resilience to changing environmental conditions. Photo by Roussel Bernard/Alamy Stock Photo
A long-term study shows the subtle hand of natural selection on Argentina’s Magellanic penguins.

Published November 29, 2016
If you ask the internet, penguins are pretty much perfect as they are: cute, curious, and clumsy. But the truth is, the “perfect” penguin might not always take the same form.

Since 1983, biologist P. Dee Boersma has been studying the world’s largest colony of Magellanic penguins at Punta Tombo, Argentina, and has found that as environmental conditions shift, the penguins show a resilience to those changes. Boersma and her colleagues have measured a lot of penguins. And they’ve been tracking whether and how everything—from their bills to their flippers to their feet—has been changing over time.

“It’s kind of like a big general census,” says Laura Koehn, a doctoral candidate in fisheries science who worked with Boersma’s team as an undergraduate.

By marking penguins with ID bands, the researchers tracked how successful each was at raising its young, which traits were passed down through the generations, and whether certain parental traits, such as a longer bill or shorter feet, led to a boost in survival for a penguin’s offspring.

In general, Koehn says, they weren’t able to detect any evidence of modern penguin evolution—yet. The penguins aren’t all getting bigger, for instance. But the team did find that, sometimes, being a certain shape or size has perks, and that these traits are passed down, which paves the way for evolution. Since different body shapes provide different benefits, what could be considered the “ideal” penguin for the conditions in any given year is fickle and variable, and often reverses itself over time. But overall, the takeaway is clear: even when conditions in their highly dynamic habitat aren’t the best, at least some Magellanic penguins will have what it takes to succeed.

Boersma’s team found evidence of natural selection—that is, when penguins of a particular size or shape raised chicks more successfully than their peers—in seven of the 28 years examined. In those years, they found that the trends for males and females seemed to be headed in different directions. Furthermore, the timing didn’t always overlap.

In years when food seemed scarce and more than half the chicks died of starvation, successful male dads tended to have larger bodies and bills, perhaps because they could catch larger prey. In years when food appeared abundant, males of all sizes raised chicks equally well.

In some years, female penguins with more petite bodies, or just with shorter feet or smaller bills, had chicks which survived better. In other years, the opposite was true.

Detecting even this small signal of ongoing natural selection is impressive, says biologist Mary Bomberger Brown, especially in a bird that splits its time between land and sea. It requires precisely tracking and measuring large numbers of individuals over long periods of time. Even then, she says, “the differences aren’t going to be gigantic. A penguin flipper isn’t going to be four inches [10 centimeters] longer one year than it was the previous year.”

“Overall, nobody’s shrinking or getting bigger,” emphasizes Koehn. Instead, these year-to-year fluctuations tend to wash out over time. That suggests, says Koehn, that whatever factors are driving these changes—whether climate, food, or even behavior—are relatively stable over time.

But if that stability is upset, the penguins have shown they have the capacity within their population to survive. “When they are pushed, they do respond,” says Brown.

Just how far and how fast that flexibility can be pushed, however, is uncertain.


Saturday, November 5, 2016

Range of penguin personalities could help species success

Bird researcher Professor John Cockrem with a blue penguin in Oamaru.
Bird researcher Professor John Cockrem with a blue penguin in Oamaru.

Scientists are spending one-on-one time with penguins to learn about the deeper sides of their personalities.

Learning more about how daring or shy penguins succeed could help guide penguin conservation, Massey professor John Cockrem says.

He is part of a research team made up of masters students from Massey University and Dr Philippa Agnew, from the Oamaru Blue Penguin Colony, that is two weeks into an eight-week study of the Oamaru penguins.

The group will take blood tests to find the amount of corticosterone hormone each penguin secretes when handled. The amount indicates where the penguins fall on a "personality spectrum" of timid and cautious, to daring and dominating.

"There's a huge range," Cockrem said. "The ones that are less sensitive to their environment tend to be the dominant more aggressive ones. They are also not so fast to change.

"The ones that are more sensitive to what's happening around them, they are more shy and are slow to explore, but they are more flexible to change."

Once the scientists have determined where each penguin falls on this personality scale they will compare this with their success in breeding, recorded in the Colony's ongoing population monitoring.
They will also use GPS to look at individuals' foraging patterns.

"The environment in which the birds live in is gradually changing. There are human influences and influences coming from climate change, so as these environmental changes occur, it may be that some animals are better able to change than other animals," Cockrem said.

However, that doesn't mean there is one perfect penguin personality.

"You might think it's good to have a high stress response, but then why aren't all animals like that?" he said.

"The hypothesis that I've put forward and that we're testing here is that in some years the dominant bolder ones might do better, but in other years the more sensitive animals, the reactive ones, will do better. There's no perfect response."

Further studies Cockrem is involved in are looking at where penguin populations in the North Island feed.

The information will be combined with the current study and past blue penguin data to help give a bigger picture of how penguin populations adapt and which feeding areas are most important for penguin conservation.

 - Stuff


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