Oceanologia et Limnologia Sinica (1998)


A pregnant finless porpoise (Neophocaena phocaenoides), whose body length (BL) was 1.63 m and body weight (BW) was 75.8 kg, gave birth to a female calf successfully in Enoshima Aquarium, Japan on April 10, 1993. The process of the parturition and its related behaviors on respiration and movement of this female, together with those of the male (BL=1.67 m, BW=58 kg) and the calf (BL=0.75 m, BW=7.2 kg) (Tab.1) in the same pool were inspected in four periods: before parturition, earlier stage of the parturition, later stage of the parturition and after parturition. The results show that before the parturition started, there was mucus coming out of female’s genital slit continually. The parturition lasted for 153.77 min and it began at 19:12. It took 141.25 min for the fluke and caudal peduncle of the calf to be delivered, but the delivery of the rest part of the calf took only 12.52 min (Tab. 2, Plate I). The average respiration rate of the mother increased to some extent before parturition to earlier stage of parturition. However, the respiration rate decreased slightly at the later stage of the parturition. The average respiration rate of the calf was 6.87 times/min and apparently higher than that of its mother (Tab. 3). There were 3 types of movements of the mother porpoise: surface movement, slow swimming (about 0.1-0.2 m/s) and fast swimming (about 1-2 m/s). With the process of parturition, the duration of the surface movement increased and swimming speed slowed down (Tab. 4). The calf’s movement was always characterized by fast swimming near the water surface. Because its sense of direction was very weak, the calf bounced pool wall 6 times during observed. In the parturition process, the mother moved along all the time. However, it swam together with the male as soon as the parturition was completed (Tab. 5). No obvious nursing behaviors were observed. Moreover, some concomitant behaviors of parturition such as jetting water (2 times), jumping (85 times), abdomen-bending (7 times), fluke swinging (7 times) and rolling swimming (4 times) were recorded at the same time. In this study, 4 aspects are worth discussing. (1) Most parturition of finless porpoise took place between April and May including the case described above. But finless porpoises in the South China Sea usually deliver their baby between August and October. Further investigations on the difference in the parturition season should undertaken in terms of the reproduction biology, evolutional and environmental features of this animal. (2) The concomitant behaviors in this study are regarded as typical parturition behaviors. Similar behaviors were reported for other dolphins. (3) The duration of the parturition was significantly longer than the case in Toba Aquarium in Japan (88 min). In order to obtain a normal mean parturition time of finless porpoise to determine whether or not a parturition is a dystocia, more cases of parturition duration should be analyzed. (4) After parturition the male finless porpoise should be kept in a separate pool, otherwise the male would disturb normal nurture processes for the calf.