Reduction of rodent fertility by plant consumption - With particular reference to Ziziphus spina-christi

The present study investigates the possibility that plants used in traditional medicine for birth control may also reduce reproduction in their natural herbivores. Ten species of plants utilized by Bedouins for birth control were selected. These were dried, ground, and mixed with the standard diet and offered to female laboratory rats. Six plant species (60%) were found to reduce reproduction rate in white female rats, and the shoots and fruit of one of the effective species, Ziziphus spina-christi, when offered to its natural herbivore, Meriones tristrami, at the level of 35% of the standard diet, postponed female puberty and significantly reduced offspring survival. Plants that are known to be an effective factor in human birth control may have similar effects on their natural mammalian herbivores. In such cases, when the seeds of the plant are part of the herbivore diet, a certain percentage of the seeds will be dispersed and germinate, while the resulting population control of the animal achieved by its consumption of the seeds will prevent overgrazing, thus maintaining a mutual balance. It is suggested that ethnopharmacological data may assist in uncovering plants that, under the following conditions, have the potential to regulate reproduction in mammalian herbivores (with implications for human reproduction): (1) the plant is an important component of the animal's diet and (2) the active secondary metabolites of the plant directly interact with the physiological systems governing reproduction in the herbivore.