If a penguin falls in the forest and no one is there to hear it, I don't know what kind of forest that is—but everyone who's interested in penguins is probably hanging out a lot closer to the South Pole. The charismatic birds let scientists and tourists alike get a close look without too much trouble. And all that familiarity has the potential to change penguins, and other closely watched animals, for good.
King penguins (Aptenodytes patagonicus) appeal to zoo visitors and cold-resistant tourists by doing miniature tuxedoed human impressions, and to researchers by diving 100 meters into the ocean or carrying their chicks on their feet to keep warm. In the Crozet Archipelago, an island chain in the far southern Indian Ocean, scientists study the penguins as well as other polar items of interest from a permanent station called Alfred Faure. For 50 years, the camp has shared a small island with a colony of more than 48,000 penguins.
A group of researchers led by Vincent Viblanc from the University of Strasbourg wondered how decades of living near the human research station has affected this population of king penguins. To find out, they studied some penguins that live close to the camp and see humans at least once a day. They compared them to penguins from farther away on the island, where humans visit once a week or less.
The researchers caught 15 penguins from the frequently bothered group, plus 18 more from the group that was mostly left alone. After taping heart monitors to the birds' backs, they rereleased them. Then they gave the birds a series of three tests designed to stress them out. The tests were done in random order over the course of two days, while the heart monitors recorded how high the birds' heart rates rose and how quickly they returned to normal.
One test involved simply walking up to a penguin. A researcher approached the target penguin from a distance while the bird watched, then stopped 10 meters away and stood still for a minute before retreating. This was meant to mimic a tourist taking pictures, or a scientist recording an observation. In a second test, a researcher snuck up behind the penguin while it wasn't watching and banged two metal bars together loudly. This test, which would exercise most humans' hearts too, was meant to represent the loud noises a bird might hear while cranes and trucks move supplies into the research station.
The final test was a capture: what happens to a penguin if researchers need to physically examine it, say, or attach a band to its flipper. Each bird was immobilized for three minutes with a hood over its head before being let go.
Looking at the results from their heart rate monitors, the researchers saw that birds from the busier side of the island weren't as bothered by the stressors they experienced often. A human walking up close, or a loud mechanical noise, didn't bother these birds nearly as much as it bothered the birds from the quieter side of the island.
This might have been because the penguins were simply used to being harassed by humans. Alternately, over the decades of human activities in the neighborhood, all the most stress-sensitive penguins might have fled to a quieter area. "In the field, we notice that some birds are more sensitive to disturbance than others," Viblanc says.
The results of the capture test suggested the first explanation was right. During their brief kidnappings, the penguins from the frequently disturbed group were just as stressed out as penguins from the quiet population. The researchers think this is because captures don't happen very often, so being captured was probably a new experience for all the penguins in the study. Loud noises and visits from humans, on the other hand, are frequent happenings for the penguins living close to the camp. These everyday stressors have become no big deal.
If human activities had driven all but the most relaxed penguins away from the site, then these remaining unflappable penguins should have been calmer than their peers during a capture. Since this wasn't the case, it seems that "the lower stress responses are not a generalized phenomenon," Viblanc says.
Why does it matter? If humans drive animals with certain traits out of a population, we're performing our own (unnatural) selection. It's the difference between teaching your dog a trick and breeding a whole new kind of dog.
Penguins that have mastered the trick of ignoring harmless humans make scientists' work easier, and keep themselves less stressed out. But if humans cause selection for more relaxed animals—here or at sites with other wild animal populations—we might be creating problems for those animals. For example, could calmer penguins be too calm when facing a predator or other threat? "It is hard to say...what the consequences may be in terms of vulnerability to predators," Viblanc says.
There's another reason researchers like Viblanc are keeping a close eye on how well-meaning scientists and tourists affect animal populations. If we force individuals with certain traits away, the whole population becomes less genetically diverse. This gives them less flexibility for adapting to new challenges in their environment. And when a real cause for worry comes along—say, climate change—we want to be sure we've left the little guys with a fighting chance.
Viblanc VA, Smith AD, Gineste B, & Groscolas R (2012). Coping with continuous human disturbance in the wild: insights from penguin heart rate response to various stressors. BMC ecology, 12 (1) PMID: 22784366
Image: A king penguin, by Liam Quinn/Flickr