Aquatic Mammals (2012)

DOI: 10.1578/am.38.2.2012.127


For many toothed whales, two predominant and multifunctional spatial positions occur between a mother/calf pair after birth: (1) the echelon position and (2) the infant position. Other nonpredominant positions also have social and developmental significance for the calf. So far, the observational period of studies on the spatial positions tends to be too short, and the studies have primarily focused on the marine groups. Moreover, few, if any, studies examining spatial relations between mother/calf pairs have been conducted on endangered toothed whale species. The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is one endangered and freshwater toothed whale. We studied the development of echelon, infant, and other position(s) in one calf maintained in captivity and two in a seminatural enclosure up to 1 y after birth. Focal following and continuous recording methods were used. A total of 180.6 h of video were recorded for the captive calf during the first year after birth (1.8 ± 0.5 h/d; n = 99 d). For the two calves in the enclosure, a total of 254.9 and 479.9 h of visual observations were recorded between 12 to 109 d after birth (5.8 ± 0.9 h/d; n = 44 d) and during the first year after birth (5.9 ± 0.5 h/d; n = 81 d), respectively. Results indicated that time spent in echelon, infant, and other position(s) accounted for 24.6 ± 2.7%, 34.4 ± 8.1%, and 4.6 ± 2.2% (n = 3), respectively. As the calves grew, they decreased their time spent in the echelon position. In contrast, time spent in the infant position increased and decreased in a parabolic fashion. The peaks (40.2%, 47.8%, and 46.8%) were approached at 91, 62, and 62 d after birth for the three calves, respectively. At 245 d after birth for the captive calf and 187 d for the second seminatural calf, time spent in the infant position began a second increase. This increase continued until the end of the year. Other positions were assumed during a small amount of time and changed slightly over time. In regards to animal management and conservation, we should regulate human activities contributing to the separation of a mother and her calf, especially before 90 d after birth. In addition, we should eliminate fishing gears and other risky factors in the environment until at least 60 d after birth.