Female rats in the wild appear to mate and conceive during a brief period of postpartum estrus, usually within the first 24 h following parturition. This shortens the interval between successive litters and can thereby greatly increase the female's overall reproductive output. This study presents a quantitative analysis of the time of onset, duration, and quality of the receptive behavior of females during this time. Females were tested for receptivity every 3 h following the delivery of the first pup. The percentage of females displaying lordosis rose rapidly from 30% at 6 h to 100% at 9 h and at 12 h. Receptivity declined steadily after 12 h, with 20% showing lordosis at 21 h. The quality of lordosis followed a similar curve. The postpartum estrus appeared to depend more upon the onset of parturition than it did upon the ambient photoperiod.

Original languageEnglish (US)
Pages (from-to)994-999
Number of pages6
JournalBiology of reproduction
Issue number5
StatePublished - 1980

All Science Journal Classification (ASJC) codes

  • Reproductive Medicine
  • Cell Biology


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