One explanation for this might be that the duration of sperm storage in female agile Antechinus is related to the likelihood that an estrous female will encounter a male to inseminate her prior to ovulation. Hence, in a population of high density where the likelihood of encountering a male during estrus is great, lengthy periods of sperm storage may not be necessary. In contrast, in populations of low density, extended periods of estrus and sperm storage may be essential in order to ensure that females encounter mates prior to the annual male die-off. Further study is required to test this hypothesis. Evidence from captive studies indicates that spermatozoa stored in the isthmus of the oviduct are viable for extended periods, although the number and fertility of sperm stored decline significantly after —10 days. buy yasmin online
Almost all females in the Powelltown population (—93.8%) had ovulated by 23 August, 18 days after the commencement of the mating period. Trapping data indicated that females were more active prior to ovulation, and hence more readily caught, than after this time. The number of females trapped per 100 trap nights in this study peaked on Days 14 and 15 of the rut (19-20 August) and declined thereafter.