The Development of Spatial Positions Between Mother and Calf of Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis) Maintained in Captive and Seminatural Environments

Abstract

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.

Aerial photographic identification of narwhal (Monodon monoceros) newborns and their spatial proximity to the nearest adult female

“…The method presented in this study could be adapted and used for any other cetacean or non-cetacean species, which are highly visible from the air and have similarly close spatial associations between mother and offspring. Among cetacean species, the closeness of the cow-calf spatial association, combined with large size and colour differences between adults and newborns, seems to be a common feature of many species with distinct geographic ranges and ecological specialization (Mann and Smut 1999;Noren and Edwards 2007;Szabo and Duffus 2008;Karenina et al 2010;Xian et al 2012;Hill et al 2013;Smultea et al 2017). Accordingly, the dichotomous key presented here and the resulting analysis of spatial associations could be applied to many other whale species with relatively minor modifications.…”

Evidence for Maternal Style Among Adult Female Dolphins When Sharing Pectoral Fin Contacts with Their Calves

“…Other physiological development markers (e.g., breath-holding and stroke rate increases; Noren et al, 2002) also correlate with maturity as a calf approaches independence from the mother; thus, changes in PFC exchanges between mothers and calves associated with calf age would not be unexpected. Use of the echelon swim position decreases as a calf matures and develops musculature that allows for more independent swimming (Gubbins et al, 1999;Xian et al, 2012). A transition to social independence, not only physical maturity, was documented for Indo-Pacific bottlenose dolphins (Tursiops aduncus) as calves aged into juvenility (Krzyszczyk et al, 2017).…”

“…This position also affords energetic swim benefits as well as close proximity to the mammary glands for more efficient nursing. As a calf develops, it shifts from the echelon to the infant swim position with mother (Gubbins et al, 1999;Xian et al, 2012). Thus, for younger calves the two primary body parts contacted could be related to swim position that has other survival benefits for the calf, rather than a selection of body part per se.…”

Altered swimming gait and performance of dolphin mothers: implications for interactions with tuna purse-seine fisheries

“…Early in life, echelon position is the dominant behavior displayed by cetacean mother-calf dyads (McBride & Kritzler 1951, Norris & Prescott 1961, Au & Perryman 1982, Taber & Thomas 1982, Krasnova et al 2006; it enables neonatal cetaceans to maintain close proximity to their mothers during travel (Norris & Prescott 1961, Lang 1966 by increasing the swimming efficiency of the infant (Kelly 1959, Weihs 2004, Noren et al 2008. As cetacean offspring increase in size, infant position becomes the dominant formation swimming strategy for mother-calf dyads (Taber & Thomas 1982, Mann & Smuts 1999, Xian et al 2012. For example, bottlenose dolphin Tursiops truncatus calves are observed in this position 38% of the time by 1 yr postpartum (Gubbins et al 1999), and this behavior remains important for calves up to 4 yr old (Gibson & Mann 2008).…”