August 3, 2016
The stress of birds'
continent-spanning annual migrations, it appears, leads to faster aging and a
potentially earlier death. A new study in The Auk: Ornithological
Advances reveals that telomeres, structures on the ends of chromosomes
that shorten with age, are shorter in migratory birds than in their
non-migratory counterparts.
Migration lets birds take advantage of abundant
food resources at high latitudes during the breeding season while escaping the
region's harsh winters. However, it's also an enormous undertaking, and the
benefits that birds gain from it come with a cost. Carolyn Bauer of North
Dakota State University and her colleagues compared the telomeres—bits of
non-coding DNA that shorten during cell division and stress—of migratory and resident birds
from the same species, the Dark-eyed Junco. They found that the migrants had
significantly shorter telomeres than birds that stayed put year-round,
suggesting that the migratory
birds were aging at a faster rate and that the stress of a
migratory lifestyle may actually shorten birds' lifespans.
"Whenever our cells divide,
we lose a little bit of DNA on the ends of our chromosomes, and telomeres are simply
non-coding regions that act as 'protective caps," explains Bauer. Once
they reach a certain threshold of shortness, the cell dies. Importantly,
exposure to stress can also make telomeres shorten faster. For their study,
Bauer and her colleagues collected blood samples from 11 migratory and 21
resident juncos in Virginia, using only first-year birds to ensure that any
telomere differences were not simply due to age. "I've been interested in
measuring telomeres since I was undergraduate at the University of
Washington," says Bauer. "I remember my introductory biology
professor lecturing about telomeres and how environmental stress could cause
them to shorten."
