Daily, alternated-day, or bi-weekly ovarian ultrasounds (General Electric - Logiq e BT9, BT12 & Logiq V2 with a 2,5–5 MHz convex probe) have been performed for the last 5 years in three female killer whales (Orcinus orca) kept at the Loro Parque facility in Tenerife, Spain and have provided invaluable complementary information on the ovarian activity in this species.1,2 To render the study possible, twelve killer whale trainers were taught how to recognize killer whale’s ovaries by ultrasound and record the data. Two females were captive born, respectively in 2002 and 2004, and one was a stranded whale estimated to be born between 2006–2007. Since 2013, over 4,500 sessions with over 32,000 ovarian ultrasound videos (both in AVI and DICOM format) have been obtained. The females had originally been receiving altrenogest (Regumate®; 0.044 mg/kg) for a long period of time (>2 years) for contraception and were then switched to 6-month treatment periods separated by withdrawal for 2 cycles. The review of the data has permitted us to identify antral follicles of much smaller sizes than previously described and the confirmation of their presence in ovaries both with and without altrenogest.1 Once growing follicles were identified they were tracked daily throughout their entire cycle and up to three times per day once they reached 2 cm in diameter, allowing for a detailed visual follow-up. A corpus hemorrhagicum could be identified in some instances. Corpora albicantia scars were consistently visualized long-term post-ovulation, a structure not yet reported in marine mammals’ ultrasounds. Follicular developments and one ovulation were seen while the animals were under altrenogest treatment. Unlike other animals a delay in follicular cycles post-removal has been described in cetaceans.1,3,4 In this study, the following irregularities and/or pathologies have been identified post-altrenogest removal: shorter cycles, longer cycles, delayed cycles, prolonged anoestrus (one animal), development of follicular cyst, retained corpus luteum, and spontaneous galactorrhea. Future research will correlate endocrine data from daily urine samples taken during the time lapse of this study.
The author wishes to thank the veterinary department and the Orca ocean trainers’ team of Loro Parque, Tenerife, Spain. This study has been made possible thanks to a grant from the Loro Parque Foundation.
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2. O’Brien JK, Robeck TR. 2010. The value of ex situ cetacean populations in understanding reproductive physiology and developing assisted reproductive technology for ex situ and in situ species. Int J Comp Psychol. 23:227–248.
3. Robeck TR, Jensen E, Brook F, Rourke N, Rayner C, Kinoshita R. 2000. Preliminary investigations into ovulation manipulation techniques in delphinids. Joint AAZV & IAAAM Conference Proceedings, New Orleans, LA; Pp. 222–225.
4. Robeck TR, Gili C, Doescher BM, Sweeney J, Laender P, Van Elk CE, O’Brien JK. 2012. Altrenogest and progesterone therapy during pregnancy in bottlenose dolphins (Tursiops truncates) with progesterone insufficiency. J Zoo Wildl Med. 43:296–308.