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Biology of Reproduction, Vol 21, 1057-1066, Copyright © 1979 by Society for the Study of Reproduction
1 Research Service, VA Medical Center,
Minneapolis, Minnesota 55417 and
Departments of Biochemistry and Entomology, Fisheries and Wildlife,
University of Minnesota, St. Paul, Minnesota 55108 The estrous cycle of 10 intact female wolves, aged 8 months-8 years at the initiation of the
study, was characterized in terms of vaginal smears, behavioral observations and serum concentrations of estradiol-17 The 7 estrous animals (260 samples) included 1 pup and 2 adults that delivered litters. Estradiol-17
2 Marshfield Medical Foundation,
Marshfield, Wisconsin 54449
3 Department of Ecology and Behavioral Biology,
University of Minnesota, St. Paul, Minnesota 55108
4 U. S. Fish and Wildlife Service,
Patuxent Wildlife Research Center, Laurel, Maryland 20811
, progesterone and luteinizing hormone (LH) from January through June.
No estrous cycles occurred in these animals between June and December. All were housed with
male wolves. Two pups and 1 adult remained anestrous during this interval. One pup and 2 adults
produced litters between May 4-6. Four adults exhibited endocrine changes similar to those of
the pregnant animals but no litters or signs of abortion were observed. The duration of proestrus
was 15.7 ± 1.6 days (X ± SEM, n = 6), of estrus 9.0 ± 1.2 days (n = 4) and of the luteal phase 63 ±
2 days (n = 6). The duration of pregnancy was between 60-65 days. The anestrous females (86
blood samples) had 6 progesterone values between 1-2 ng/ml and the remainder below 1 ng/ml.
Their estradiol-17 concentrations varied between 5-20 pg/ml. Values for LH varied between
0.1-2 ng/ml, except for 1 value above 15 ng/ml for each of the 2 anestrous pups on 12 January. varied between 10-20 pg/ml during proestrus, peaked at 30-70 pg/ml late in proestrus
and fluctuated between 10-30 pg/ml during pregnancy or the duration of luteal activity in the
nonpregnant animals. The preovulatory LH rise, 5-15 ng/ml, extended over 3 days during and
immediately following the peak estradiol-17 values. An earlier elevation in LH was observed in
3 of the estrous animals. Progesterone began increasing during the LH surge and peaked 11-14
days later at 22-40 ng/ml. Progesterone concentrations greater than 3 ng/ml were maintained for
56-68 days in 6 of the 7 animals exhibiting estrus. Progesterone concentrations declined at parturition but continued to fluctuate between 0.2-3 ng/ml for 3-6 weeks.
Note:
ACKNOWLEDGMENTS
We deeply appreciate the cooperation of the
Minnesota Department of Natural Resources and in
particular, Lloyd Knutsen and Roger Johnson. The LH
antiserum was generously supplied by Dr. Gordon
Niswender. Invaluable assistance in collection of these
samples was provided by students Kris Miller, Diane
Boyd, Nan Kane and Rick Chapman. We also wish to
thank Nancy Manning, Chuck Schmoller and David
Hupe for their technical expertise and Judith Morin
for preparation of the manuscript.
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