Serum progesterone profiles and corpora lutea of pregnant, postpartum, barren and isolated females in a laboratory colony of woodchucks (Marmota monax).

Female woodchucks, greater than or equal to 1 year old (n = 10) or recently weaned locally in the wild at 42 degrees N (n = 10), were maintained indoors in standard laboratory animal facilities from one summer solstice to the next except for those killed after 11 months of study. Available ambient light was supplemented with a 12L: 12D incandescent light schedule. Food and water were provided ad libitum, except for a 63-day period when feeding and supplemental lighting were discontinued, starting at the winter solstice . Temperatures fluctuated with outdoor temperatures greater than or equal to 4 degrees C. During the winter, females within each age class (adult vs. subadult ) were housed with (n = 5) or without (n = 5) a male cagemate , and scored for hibernation at variable intervals. Blood samples for serum progesterone assay were collected at intervals of 1-4 weeks. Birth of litters occurred in 2 of 5 adults (March 19, April 2) and in 0 of 5 subadults . Neither the incidence nor frequency of hibernation were correlated to the occurrence of pregnancy or to the extent or timing of elevations in progesterone in barren or isolated females. Serum progesterone was elevated during the 31-day gestation and for 1-2 months postpartum in the 2 fertile colonized animals and in 7 others captured pregnant during the same breeding season and which gave birth April 12-24. Postpartum animals had progesterone levels equal or above those near midgestation and had 3.1 +/- 0.2-mm diameter corpora lutea which numbered 2.5 +/- 0.3 per ovary.(ABSTRACT TRUNCATED AT 250 WORDS)