Holarctic Marmots as a factor of Biodiversity.
Rumiantsev V.Yu;, Nikol'skii A.A. & Brandler O.V. eds.,
Abstracts of the
Conference on Marmots (Cheboksary, Russia, 25-30 August 1997), Moscow ABF 1997, 216p.


PROGESTERONE CONCENTRATIONS IN WILD-CAUGHT YELLOW-BELLIED MARMOTS



K.B. Armitage*, K.E. Wynne-Edwards**

* Department of Systematics & Ecology, The University of Kansas, Lawrence, USA
** Department of Biology, Queen's University, Kingston, Canada



Blood samples were collected from wild-caught yellow-bellied marmots (Marmota flaviventris) during the active season from 1989 to 1993, inclusive. At the same time, the nipple index of adult females was scored as 3 (nipples visible), 4 (nipples prominent), 5 (nipples swollen), or 6 (lactating). Because the timing of reproduction varies from year to year, the results were standardized to the period of the reproductive cycle: pre-gestation, gestation, lactation, and first-four-weeks post-lactation. The termination of lactation was set at the time of the first emergence of young aboveground. The adult females were divided into three groups: (1) reproductive, those females that weaned a litter, N=50; (2) non-reproductive, those females that failed to wean a litter and whose nipple index indicated no initiation of reproduction, N=57; (3) failed reproduction, females that failed to wean a litter but whose nipple index indicated that reproduction was initiated.

For reproductive females, progesterone concentrations increased from pre-gestation to a peak in early gestation, then decreased during the last two weeks of gestation, then increased to a peak in mid lactation and declined thereafter. Nipple index increased throughout the reproductive period to a peak in late lactation and early post-lactation and declined thereafter. Mean progesterone concentration was highest during lactation (Table 1).

Progesterone concentrations of non-reproductive females were always much lower than those of reproductive females (Table 1). Nipple index was lower than that of reproductive females and remained low throughout the reproductive period.


Table 1.
Progesterone concentrations (ng/ml) for M. flaviventris.
Values are mean SE (N) N = number of females.

GestationLactationPost-lactation
Females
Reproductive2.40±0.26 (40)2.57±0.50 (31)0.84±0.24 (14)
Non-reproductive0.51±0.13 (35)0.47±0.08 (30)0.14±0.04 (13)
Failed reproduction1.64±0.23 (9)0.51±0.15 (4)0.48±0.11 (4)
Yearling0.92±0.37 (6)4.13±1.78 (8)0.29±0.19 (4)
Males
Adult0.12±0.05 (31)0.17±0.05 (24)0.11±0.05 (13)
Yearling0.18±0.18 (4)0 (3)0.12±0.12 (3)
Yearling0.18 ±0.08 (5)

Progesterone concentrations of failed-reproduction females were higher than those of non-reproductive females and lower than those of reproductive females (Table 1). The peak value occurred in late gestation and a second peak occurred in late lactation. Nipple index was higher than that of non-reproductive females and lower than that of reproductive females except during gestation.

Progesterone concentrations of males and juveniles were always low and those of non-reproductive yearling females were higher than those of non-reproductive females and were unusually high during lactation (Table 1).

The pattern of progesterone concentrations differs from that of most small mammals,but is similar to that of M. monax and Spermophilus beecheyi.


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