First Observation of Pregnancy and Parturition in a Captive Pantropical Spotted Dolphin (Stenella attenuata)

Abstract. A female pantropical spotted dolphin (Stenella attenuata) successfully mated with a mature male in captivity on April 13, 2017. This mating event was followed by an evaluation of the plasma progesterone concentration, appetite, and rectum temperature of the dolphin during pregnancy. We recorded the progesterone profiles during pregnancy, the gestation period, and the parturition events. The progesterone level (ng/mL) ranged between 0.7 and 133.4 (n = 27), and the average was 45.1 (SD = 38.5). Immediately after mating, extremely high progesterone levels were observed, which showed a decreasing trend towards the parturition day. The gestation period was 352 days. On the morning of the parturition day on March 31, the female displayed symptoms such as a drop in rectal temperature by approximately 1°C and reduced appetite. The time from the first observation of vaginal discharge to the fluke's appearance was 5.5 hr, while the subsequent period until birth was 4 hr in length. The time from parturition to the first successful nursing was approximately 4 hr, while the time from the nursing to the placental passage was less than 1 hr. To the best of our knowledge, this is the first report on the pregnancy period of pantropical spotted dolphins in captivity.