The Whitten effect is stimulation, by male pheromones, of synchronous

estrus The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestrous ...

in a female population. Social signals, or social stimuli, have an effect on reproduction in all mammals. For certain female mice, the

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

s contained in the urine of male mice can be such stimuli, inducing

synchronous Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...

.Ochiogu, Izuchukwu S., Chike F. Oguejiofor, and Ambrose N. Nwagbo. "Males' Non-Enhancement of Bruce and Whitten Effects in Female Mice – Mus Musculus." Animal Research International 6 (2009): 1077-081. When the pheromones contained in the urine of male mice stimulate synchronous estrus in a population of female mice, it is known as the Whitten effect. This is a phenomenon observed by Wesley K. Whitten (1956, 1966, 1968), whereby male mouse pheromone-laden urine synchronizes the estrus cycle "among unisexually grouped females," and is an example of male-to-female pheromonal effects in mice, similar to the

Bruce effect The Bruce effect, or pregnancy block, is the tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male. The effect was first noted in 1959 by Hilda M. Bruce, and has primarily been studied i ...

.Jemilio, Bozena, Scott Harvey, and Milos Novotny. "Promotion of the Whitten Effect in Female Mice by Synthetic Analogs of Male Urinary Constituents." Proceedings of the National Academy of Sciences of the United States of America 83 (1986): 4576-579. The Whitten effect occurs when a group of female mice are exposed to the urine produced by a male mouse. The male’s urine contains certain volatile, or airborne, pheromones that affect the hormonal processes of the females that control their reproductive status. A sexually mature and viable male must produce the urine, as the pheromones that produce the Whitten effect are dependent on male sex hormones such as testosterone. The female mice do not require direct contact with the male’s urine to produce the Whitten effect, as the pheromone contained in the urine is airborne and therefore is taken up by the females through their olfactory system.Gangrade, B.K., and C.J. Dominik. "Studies of the Male-Originating Pheromones Involved in the Whitten Effect and Bruce Effect in Mice." Biology of Reproduction 31 (1984): 89-96. The reproductive cycle of female mice in isolation is approximately 4 to 5 days, and the reproductive cycles of grouped females are often longer and more irregular.Ma, Weidong, Zhongshan Miao, and Milos V. Novotny. "Introduction of Estrus in Grouped Female Mice (Mus Domesticus) by Synthetic Analogs of Preputial Gland Constituents." Chem. Senses 24 (1999): 289-93. However, when grouped female mice are exposed to the pheromones contained in a male’s urine, the Whitten effect occurs, and the majority of the female mice will enter a new estrus cycle by the third day of exposure. However, there is little evidence for a similarly functioning vomeronasal, or olfactory, system (thought to be the sensory organ that initiates the Bruce, Vandenbergh, and Whitten effects) in humans. These differences, in putative stimulus and neural pathway (as well as species observed), stringently distinguishes the Whitten and McClintock effect, as the latter does not posit a role for male pheromones.

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* Journal code: 0375363 * * * * {{DEFAULTSORT:Whitten Effect Ethology Menstrual cycle

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