Endocrine correlates of hibernation-independent gonadal recrudescence and the limited late-winter breeding season in woodchucks,Marmota monax
✍ Scribed by Concannon, P. W. ;Baldwin, B. ;Roberts, P. ;Tennant, B.
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 363 KB
- Volume
- 256
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Woodchucks (Marmota monax) normally experience gonadal recrudescence towards the end of a 4-5 month hibernation, emerge in late winter, immediately breed in a short 3-week breeding season, and have regressed gonads before the next hibernation. Our studies of wild and captive animals show that fertile females give birth to single litters after a 32-day gestation and their breeding season is terminated by a reactivation of the corpora lutea of pregnancy for 1-3 months immediately postpartum. In nonbred females the breeding season is likewise terminated by spontaneous luteinization of the ovaries for 1-3 months shortly after the vernal equinox. Tests regress and testosterone declines during and after the breeding season. Circannual reproductive cycles persist in the absence of hibernation and are shortened to 9-10 months after 3-5 years of a 12L:12D photoperiod. Unique aspects of this species that merit endocrine investigation include descent/retraction of testes, transient luteolysis at parturition, superactivation of postpartum corpora lutea, regulation of the pituitary-gonadal axis by an annual endogenous metabolic cycle entrained to the annual change in photoperiod, and the hormonal basis of hibernation.