Hormonal and behavioral relationships during estrus in the giant panda

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Abstract
Nonlactating female giant pandas experience a single estrus during the spring mating season. Although both hormonal and behavioral aspects of estrus have been reported on captive females, little is known about the relationship between them. Data were collected on a single captive female during three successive seasons, revealing a high degree of regularity in both estrogen profiles and the temporal pattern of associated behaviors. The birth of a live cub in the last of the three seasons, using artificial insemination, confirmed the time of ovulation as occurring shortly after a peak in urinary estrogen values. In this study, we examined the occurrence of female scent marking, rear presentations, chirp and bleat vocalizations, and the tail‐up display, and plotted their occurrence relative to the underlying estrogen values. We conclude that the role of estrogen in the expression of these behaviors is neither simple nor directly causal. Temporal associations indicate that a triggering rather than a maintenance function for estrogen is implicated. This analysis provides a clear identification of estrous behaviors, but in both the time and form of occurrence these behaviors most likely vary between females and seasons. Zoo Biol 20:537–543, 2001.