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Effects of testosterone on the synchoronization of activity rhythms to low amplitude zeitgebers in an arctic breeding songbird

Status Current
Seeking Researchers No
Start Date 11/01/2010
End Date 06/30/2011
Funding Source Fran Ulmer Award
Funding Amount 3,140
Community Partner
Related Course
Last Updated 03/01/2011 11:41PM
Keywords circadian rhythms, zeitgebers, lapland longspur


  Loren Buck

Student Researchers
  Brady Salli


A key feature of polar environments is the continual presence of the sun above the horizon; at Barrow, AK this equates to ca. 12 weeks of polar day conditions lasting from the middle of May to early August. During this time, many arctic animals, such as caribou (Rangifer tarandus tarandus), abandon diel rhythms of activity. However, arctic migrant birds continue to display a distinct circadian rhythm despite continuous daylight experienced on breeding grounds. It is hypothesized that the persistence of diel rhythms involves entrainment to low amplitude zeitgebers that include small changes in light intensity or spectral quality of sunlight that occur over the polar day. We determined previously that captive Lapland longspurs (Ca/carius lapponicus), an arctic migrant songbird, failed to entrain to light regimes that mimicked daily changes in light intensity or color temperature of polar-day conditions in Barrow, Alaska, (71 0 N), where birds were captured. Because birds were in non-breeding condition, it is possible that sensitivity to polar-day zeitgebers is increased during the breeding season and is proximately regulated by sex steroids. My current experiment tests this hypothesis through administration of either exogenous testosterone (experimental group) or empty implants (control group) to nonbreeding male Lapland longspurs and exposing them to the light regimes described above. Results of this study will elucidate a potential hormonal role in the regulation of entrainment within the biological clock of a high-latitude breeding species.

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