科学美国人60秒:乌鸦吃芝士汉堡后胆固醇会升高

This is Scientific American 60-second Science, I'm Christopher Intagliata.
High cholesterol affects a third of American adults. But it's not just us! Studies have indicated that cholesterol is also on the rise in other animals.
"And in all of these studies the idea was, well, they hypothesised that it was probably due to interactions with people and eating our food, but they didn't actually show that."
Andrea Townsend is an avian ecologist at Hamilton College in upstate New York. And she found that urban crows did have higher cholesterol than rural crows.
But then she took the next logical step in her research. She went to McDonald's. "We'd pick up 125 burgers at a time. Once one of them wanted to know what we needed all these burgers for, and I started to explain, but they just kind of waved me away halfway through. So..."
Of course, she needed all those cheeseburgers to feed crows and to monitor their diet—to determine if eating our fast food really does raise the birds' cholesterol.
"So the way you 'supplement your nestlings' is: we'd go to their nest trees, we'd toss the cheeseburgers, three to five a day, under their nest trees. And the parents would immediately swoop down, pick up the burgers and bring them to their nestlings."

And as you might expect, crows that dined on cheeseburgers did indeed have higher cholesterol than crows who did without. But here's the surprising thing: higher cholesterol didn't affect crows' chances of survival over a three-year period. And in one population, birds with higher cholesterol were arguably in better condition than other crows. Meaning chubbier.
The results are in the journal the Condor.
Crows can live more than 15 years, and Townsend says maybe a high-cholesterol diet makes its mark later in life, as it does in humans. And if you're still wondering, "Why study this?"
"I would say this is an important question, because there are lots of other species that also live in urban areas and eat our food. And some of them are endangered. So it is an important question: How will our food affect the health of wild animals?"
And as we urbanize more of the globe, our dietary influence might have even wider effects.
As for Townsend, crows are known to be highly skilled at recognizing humans, and she says the study made her a celebrity.
"During this study, especially when I was walking around, the crows would follow me around campus. They often just follow me around campus anyway; they follow my car. I was getting some notoriety on a broader scale with crows. So I would be going to... like getting gas, and the crows in the gas station would be cawing a special caw just for me. It seemed like a recognition caw. So it's like 'caw caw caw.'"
After all, a free lunch sure does seem like something to squawk about.
Thanks for listening for Scientific American — 60-Second Science. I'm Christopher Intagliata.