Abstract: Parturition events in cetaceans are difficult to observe in nature and scarcely described in detail. Observations from animals in captivity offer the possibility to follow complete gestations and to obtain a precise description of the series of events pertaining to pregnancy and parturition. After a gestation period of 11 mo, the parturition of a harbor porpoise (Phocoena phocoena) was observed for the first time at the Danish research facility Fjord & Boelt on 8 August 2007. Five prepartum signs useful to predict the onset of parturition were identified: (1) decrease in appetite (from 5,064 Kcal/d to 907 Kcal/d at 2 d before birth [B-2]), (2) unusual behavior (disinterest in training sessions, seeking of physical contact with the trainers, restlessness), (3) decrease in body temperature of 1.6º C at B-1, (4) swollenness in the genital area, and (5) increase in the inter-mammary distance (from 5 to 8 cm at B-1). During labor, three stages described for other mammals in literature were observed and each stage's duration recorded: Stage 1 was characterized by uterine contractions and dilation of the cervix (between 2 h 19 min and 7 h 39 min), Stage 2 started with the rupture of fetal membranes (1 h 42 min at least), and Stage 3 comprised the expulsion of the fetus and its membranes (7 h). The total duration of the parturition was at least 16 h 21 min as there is an uncertainty in regards to the exact beginning of the labor. The sequence of visible events occurring during parturition was as follows: apparition of the amniotic sac, apparition of the calf's flukes, apparition of the peduncle, delivery of the calf, and expulsion of the left horn of the placenta followed by the right horn. As described for other cetaceans, the delivery was caudal.
Contractions seemed to be longer and more frequent during the first stage and during the beginning of the second stage of labor. The contractions then shortened and became more regular during the expulsion of the calf. We observed that the expulsion of the calf was not provoked only by contractions but helped at the end by a violent rotational movement of the mother that broke the umbilical cord. The female's breathing rate increased dramatically towards the end of the expulsion of the calf.
Key Words: cetacean, reproduction, parturition stages, labor, contractions pattern, harbor porpoise, Phocoena phocoena
Document Type: Research article
Page Numbers: 473-480