Control of annual reproduction in the female harbor seal, Phoca vitulina ...
It was noted recently that the annual timing of the birth season varies regionally in the harbor seal Phoca vitulina. In any one area births occur once a year during a 1 - 2 1/2 month period but between areas vary by up to 5 or 6 months with clinal variations over much of the species distribution. T...
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| Format: | Text |
| Language: | English |
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University of British Columbia
2011
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| Online Access: | https://dx.doi.org/10.14288/1.0101180 https://doi.library.ubc.ca/10.14288/1.0101180 |
| Summary: | It was noted recently that the annual timing of the birth season varies regionally in the harbor seal Phoca vitulina. In any one area births occur once a year during a 1 - 2 1/2 month period but between areas vary by up to 5 or 6 months with clinal variations over much of the species distribution. To explain these variations, this study describes the reproductive cycle of female harbor seals and investigates the factors which control reproductive timing. The study is divided into one field project and two laboratory experiments. The field project decribes the annual pregnancy and nonpregnancy cycles and discusses the role of negative steroid feedbacks from the corpus luteum and/or placenta in annual reproductive timing. It is based on a macroscopic and microscopic examination of 135 adult genital organs collected in southeastern Vancouver Island. The first laboratory experiment describes the estrous cycle of 15 captive adults based on vaginal smears and vaginal and uterine biopsies. These females were ... |
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