Abstract

Difficulties with breeding control have prompted investigation of the estrous cycle and breeding season length of Australian fur seals in captivity at Royal Melbourne Zoo, Australia. Melbourne Zoo houses seven mature female Australian fur seals and one fertile mature Australian fur seal bull. Pregnancy has been prevented by separation of the male during the wild breeding season period from November through late January. Housing difficulties with this 3-mo separation arrangement have encouraged further research into the normal estrous pattern and the length of possible breeding time. Data on wild Australian fur seals suggest that females may only ovulate once during the breeding season, at which time they are usually mated, and the time of ovulation is variable within that breeding season. Little information is available on the pattern of the estrous cycles if an ovulation passes without fertilization.

Noninvasive techniques to measure progesterone for estrous cycle characterization were sought due to the impractical nature of regular conscious serum collection. Feces and saliva were considered the two most accessible and reliable sample materials. Fecal and saliva samples were collected from three females with proven breeding history from October onwards. In addition, collections from two younger females began in February.

Seals were trained for an open mouth presentation at the beginning of the feeding session twice daily on collection days. Saliva was collected using sterile cotton-tipped applicators. Saliva was spun off the swabs by a centrifuge and then frozen at -20°C until processing time. Samples were sent to the Veterinary School, University of Melbourne, for processing; progesterone analysis was conducted using the coat-a-count serum progesterone kit. Collection of saliva occurred routinely 3–4 times/wk; however, sample quantity was dependent upon individual compliance.

Identification of an individual’s feces was achieved by installation of colored inert plastic beads into individual’s food on a daily basis. Fecal samples were collected opportunistically with minor manipulation of night housing arrangements. Fecal collection difficulties occurred regularly as a result of defecation in water. Collected feces were stored at -20°C. Fecal samples were sent to the biochemistry division of the University of Vienna and results were derived from the 20-oxo-pregnane assay.

Current saliva progesterone assay results suggest an ability to predict an estrous cycle in individuals. Fecal progesterone assay results suggest an ability to detect a corpus luteum in correlation with saliva results. Further results are pending and are expected to predict the cessation of estrous activity in individuals and consequently a time limit to yearly breeding ability. In addition, the results should allow determination of the accuracy of the two techniques for prediction of estrous cycles in the Australian fur seal and possibly for other otariid seals.