Circadian performance of suprachiasmatic nuclei (SCN)-lesioned antelope ground squirrels in a desert enclosure.
Circadian activity parameters of 53 white-tailed antelope ground squirrels, Ammospermophilus leucurus, were measured to determine the role of the suprachiasmatic nuclei (SCN) pacemaker in their health and survival. Wheel-running activity was monitored in the laboratory with 44 individuals to document the presence of free-running circadian rhythms and ability to entrain to light-dark cycles. Twenty-two individuals were returned to the desert site of origin, including 12 intact control animals and 10 animals whose circadian timing had been disrupted by SCN-lesioning. Time of activity was recorded continuously for 15 days in a large outdoor enclosure by a motion detector, a microchip transponder detector, and video surveillance. An unplanned nighttime attack by a feral cat resulted in the death of 60% of the SCN-lesioned animals and 29% of the control animals in the enclosure. Surface activity of SCN-lesioned animals at the food cache occurred both in daytime and at night, ranging from 16.0% nighttime activity for one partially lesioned individual to 52.1% for one completely lesioned animal. Controls were strongly day-active, with nighttime surface trips constituting only 0-1.3% of all excursions to the cache. Nine wild free-ranging individuals, including one with a radiotransmitter collar, were exclusively day-active. One of the functions of the SCN in mammals may be to reduce activity of animals during times that are unfavorable for activity.
DeCoursey
P J
PJ
Department of Biological Sciences, University of South Carolina, Columbia 29208, USA. Dcoursey@Biol.SC.edu
Krulas
J R
JR
Mele
G
G
Holley
D C
DC
D000818:Animals; D000830:Animals, Laboratory; D000835:Animals, Wild; D002415:Cats; D002940:Circadian Rhythm / Q000502:physiology*; D003889:Desert Climate; D005239:Fear / Q000502:physiology; D005260:Female; D008027:Light; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011235:Predatory Behavior / Q000502:physiology; D012589:Sciuridae / Q000502:physiology*; D012931:Social Environment; D013493:Suprachiasmatic Nucleus / Q000502:physiology*