Keeping Time under the Midnight Sun: Behavioral and Plasma Melatonin Profiles of Free-Living Lapland Longspurs during the Arctic Summer

N.AshleyDr. Noah T. Ashley is an Assistant Professor at the Department of Biology at Western Kentucky University. He has a passion for Arctic Biology which started when working in Alaska as a graduate student. After receiving his Ph.D., he had the rare opportunity to work as a wildlife biologist up on the North Slope of Alaska for a number of years.

Dr. Ashley’s current research interests involve understanding vertebrate sleep, as well as the hormonal and immunological mechanisms that underlie sleep loss and biological rhythm disruptions in mammals and birds. He recently published a paper titled: Keeping Time under the Midnight Sun: Behavioral and Plasma Melatonin Profiles of Free-Living Lapland Longspurs during the Arctic Summer’ in the Journal of Experimental Zoology.

Background of the study

I was funded by the National Science Foundation Office of Polar Programs to understand the biological rhythms of a common arctic-breeding songbird, the Lapland Longspur (Calcarius lapponicus), in Barrow, Ak (71 °N). At lower latitudes, the light/dark cycle serves as the primary environmental cue that synchronizes daily biological rhythms. However, this cue is noticeably lacking for animals that reside north of the Arctic Circle during the summer and winter months, where continuous daylight or darkness, respectively, prevails. This raises the question of how animals deal with these extreme conditions, and how their biological rhythms are correspondingly affected.

Findings

Lapland longspurs are able to maintain a distinct daily activity rhythm despite encountering constant light conditions throughout much of their breeding season. Birds are active for 20 hours a day, and then only rest or sleep for the remaining 4 hours. In addition, there were dampened yet detectable blood concentrations of melatonin, which is a hormone that is normally secreted from the pineal gland only at night. These findings were surprising considering that other polar-dwelling animals exposed to constant polar day (or night) will abandon rhythms all together.

The question remains as to what specific environmental cue(s) these birds are using to synchronize their daily rhythms. Although only correlational, daily cycles in light intensity and ambient temperature were negatively associated with melatonin concentration in the blood, suggesting that these environmental cues could synchronize daily rhythms. However, these cues are not incredibly reliable due to unpredictable inclement weather (e.g., storms) that routinely occurs in the arctic environment that can drastically alter photic and thermal conditions. I suspect that there is a combination of cues, including social interactions, that are driving these rhythms, but experimental studies are needed.

Female Lapland Longspur
Female Lapland Longspur

 

Male Lapland Longspur
Male Color-Banded Lapland Longspur

Implications

These findings have direct applications to how humans deal with aberrant light conditions. Before the discovery of electricity, humans residing in the Arctic had to alter their daily activity cycles to accommodate these extreme photic conditions. How this is accomplished on a physiological level is still very much a mystery. In addition, seasonal affective disorder, a type of depression, is linked with seasonal changes in the light/dark cycle, and as global urbanization increases, light pollution (during the night) has been shown to contribute to poor human health outcomes. Perhaps understanding how other animals cope with extreme or abnormal light conditions could help facilitate the development of more effective therapies for humans.

These findings also lead to other questions:

  • How important is daily sleep for animals? 
  • Does sleep loss in these birds lead to serious consequences, like cognitive, immunological, and metabolic impairments as observed in humans?

Only future experiments and studies will help us shed light on these questions.

Advice from the field

My research involves both field and laboratory research. Thus, my advice for students interested in this type of research is to find a study organism(s) that you enjoy working with in a natural or captive setting, and to get as much experience working with a mentor (professor, graduate student) in these settings. Also, for chronobiology studies, you have to be comfortable with conducting research at all hours, including late at night!

About the department

The Department of Biology at Western Kentucky University (WKU) is comprised of 26 regular faculty and academic professionals, approximately 60 full-time M. S. students and 600 undergraduate majors. Furthermore, our reach extends from our campus laboratories, to our local field sites including the 1300 acre Upper Green River Biological Preserve, all the way to the Caribbean, China, and Africa. From studies on microbes to megafauna, and genes to ecosystems, undergraduate and graduate students play an active role in the advancement of knowledge taking place in the Department of Biology at WKU.