Spontaneous and induced ovulation in the lion (Panthera leo)

Publication Type:
 Journal Article
Year of Publication:
 1994
Authors:
 Ralph Dee Schramm, Michael B. Briggs, Jerry J. Reeves
Publication/Journal:
 Zoo Biology
Publisher:
 A Wiley Company, Inc., Wiley Subscription Services
Keywords:
 , ,
ISBN:
 1098-2361
Abstract:

Abstract 10.1002/zoo.1430130403.abs The objective of this study was to clarify if ovulation occurs spontaneously, if it is copulation-induced, or if a combination of both mechanisms controls ovulation in African lions. Five female lions were either permitted unrestricted copulatory activity with vasectomized males throughout estrus or were physically isolated from conspecifies for the duration of estrus. Each female was randomly exposed to each treatment in a switchback design during consecutive estrous cycles. Serum concentrations of progesterone were determined in blood samples collected on days 2, 8, 12, and 16 following the onset of estrus (day 0). Ovulation was indirectly confirmed by elevated serum concentrations of progesterone on days 8, 12, and 16. While ovulation occurred spontaneously in one of five isolated lions, five of five of the same lions ovulated following copulation (P ≤ 0.05). Following mating, concentrations of progesterone increased six- to twelve fold (up to > 109 ng/ml) between days 2 and 12, while in the same lions failing to ovulate following isolation, progesterone concentrations did not exceed 11 ng/ml by day 16. Inter-estrous intervals following mating (67 ± 4.4 days) were longer (P ± 0.05) than those following isolation (19 ± 1.0 day). Thus, ovulation in African lions appears to be induced by copulatory stimuli or some other form of physical or social interaction with conspecifies during estrus but can occasionally occur spontaneously. The lion, therefore, does not appear to be a classic spontaneous ovulator but rather a reflex ovulator like the domestic cat. © 1994 Wiley-Liss, Inc.

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