Observations of parturition in humpback whales (Megaptera novaeangliae) and occurrence of escorting and competitive behavior around birthing females

Abstract

Documented cases of cetacean births in the wild are rare. While there are currently no direct observations of a complete humpback whale birth, they are one of the few large whale species where observers have been present during a birthing event. We compiled eye‐witnessed accounts of all known humpback whale birthing events and found nine well‐documented cases globally (three published and six “new” unpublished). In two‐thirds of the accounts another “escort” whale was present and in close association with the birthing female, and of these, most cases involved multiple escorts (n = 4). We describe details of birthing events, including mother, neonate and escort(s)’ behavior, neonate appearance, and discuss reasons for escort presence during parturition. We note that immediately postpartum: (1) blood and/or placenta were not always apparent during above water observations, (2) females often (but not always) supported calves at the surface, (3) constant travel and tail slapping were typical neonate behaviors, (4) two cases of temporary calf abandonment (<10 min), and (5) evidence of shark scavenging (of placenta) and possible predation attempts (of neonate). Lastly, we suggest curled tail flukes as an additional trait for identifying neonates and note that fetal folds are not always evident in newborn humpback whales.

Round-trip migration and energy budget of a breeding female humpback whale in the Northeast Atlantic

“…Calving is generally expected in calm, shallow coastal or bank waters [65][66][67][68][69] and not in exposed oceanic waters. However, the observed changes in movement (i.e., from fast to very slow movement followed by a period of continuous movement at reduced speed) are consistent with the behavior reported from earlier observations of calving events [65,66,70]. Newborn calves have been documented outside of the described main breeding grounds elsewhere [26,71] and historical whaling records from Norway include records of late-stage pregnancies in Norwegian waters during winter and spring [72], also indicating humpback whales from this region might give birth shortly after these observations were made, likely outside breeding grounds [73].…”

First direct observation of a successful southern right whale (Eubalaena australis) birth in South African coastal waters

“…In general, the maternal behavior during the parturition described here is similar to the behavior observed in other successful cetacean births, which may include thrashing (Zani et al, 2008), arched back positions (e.g., Weilgart & Whitehead, 1986), lurching and tail spasms (e.g., Leatherwood & Beach, 1975), and rotating (Stacey & Baird, 1997). No maternal assistance for calf surfacing immediately after birth was observed, as opposed to what has been documented in some other baleen whale birthing events (e.g., Ferreira et al, 2011; Zani et al, 2008), but not in all (see Foley et al, 2011; Ransom et al, 2022). Although it is difficult to determine when labor truly began, the behavior identified by the crew as a parturition event was short (<2 min) possibly explaining why these birthing events are so rare to observe and document (Ransom et al, 2022).…”

Seasonal gain in body condition of foraging humpback whales along the Western Antarctic Peninsula

“…We examined how the body size (BAI and TL) of lactating mothers' influences the body size of their respective calves'. In this study, humpback whale calves ranged in length from 7.5 to 10 m (mean= 8.5 m), while on the breeding grounds, humpback whale calves ranged between 4 and 8 m in length, with a presumed birth length between 3.96 and 4.57 m (Clapham et al, 1999;Ejrnaes and Sprogis, 2022;Ransome et al, 2022). We found that calves' TLs were positively related to their mothers' TLs, meaning longer calves were associated with longer mothers (Figure 5).…”