Coastal residence periods and reproductive timing in southern right whales, Eubalaena australis

Abstract

The duration and timing of coastal residence of individually identified southern right whales at a principal aggregation area on the southern Australian coast differed markedly between females with calves and unaccompanied whales. The mean residence period of females that calved within the aggregation area was 70.9 days, with mean residence mid‐points of 20 August in 1993 and 22 August in 1994. In contrast, unaccompanied adults remained resident for an average of only 20.4 days with mean residence mid‐points of 27 July and 11 August in 1993 and 1994, respectively. Whales have been sighted at this aggregation area from mid May to late October (approx. 160 days), although the effective calving season (95‐100% of calves born) lasted only 88 days in 1993 and 96 days in 1994. The mean birth date based on first sighting with neonatal calf, and corrected for sightability bias, was 15 July in 1993 and 17 July in 1994, with 100% of calves born before 31 August 1993 and 23 September 1994. The time between birth and dispersal from the aggregation area, at or just prior to the commencement of the southward migration, was highly variable. Calves bom before the mean calving date averaged 80 days within the aggregation area, twice as long as those born after the mean (40 days). The large number of calves estimated to be less than 14 days old at first sighting, combined with the sighting of 26 pregnant females prior to parturition, suggests the majority of births occurred within, or very near to, the aggregation area.

Female southern right whales Eubalaena australis: Are there reproductive benefits associated with their coastal distribution off South Africa?

“…The use of calving intervals in this paper as an indicator of reproductive success is supported by the higher proportion of unsuccessful calving intervals occurring in inexperienced mothers. The tendency for reproductive success (measured as either surviving offspring or variations in the sex ratio) to increase with age is a welldocumented phenomenon, predicted by life history theory (Stearns 1992 Bins or groups of bins the coast within a season (Burnell & Bryden 1997, Best 2000a. Thus it is possible that the bin in which a whale is photographed with a calf in October is neither the bin in which the calf was born nor the bin in which it spent its early post-natal period (when calves are at their most susceptible).…”

“…Bins or groups of bins (Burnell & Bryden 1997, Best 2000a. Thus it is possible that the bin in which a whale is photographed with a calf in October is neither the bin in which the calf was born nor the bin in which it spent its early post-natal period (when calves are at their most susceptible).…”

Body shape changes associated with reproductive status, nutritive condition and growth in right whales Eubalaena glacialis and E. australis

“…However, there is no evidence that the mothers feed while in the calving habitats, and as such, must rely on endogenous reserves to support the metabolic requirements of their calves and themselves during the initial months of lactation. Mean and maximum residence times in the nursery waters for mothers and calves were reported for several E. australis populations (mean ± SD, maximum): Australia = 70.9 ± 30, 108 d (Burnell & Bryden 1997); Argentina = 77 ± 36, 170 d (Rowntree et al 2001); South Africa = 59 ± 3.9, 105 d (although this mean is probably underestimated owing to subsequent sightings outside of the study area; Best 2000). The 6 mothers measured in more than 1 mo here were part of the Best (2000) analysis; their mean residence times in the study area was 69.5 ± 9. australis that lasted from 9 to 22 d. Therefore, for 2 to 5 mo, the source of sustenance for mother and calf right whales is the mother's endogenous nutrient reserves.…”

Swim Speed, Behavior, and Movement of North Atlantic Right Whales (Eubalaena glacialis) in Coastal Waters of Northeastern Florida, USA

“…Shore-based observations of right whale behavior have been reported from other locations, including South Africa [31], Australia [35], and Argentina [36]–[39]. Here, for the first time, observations from the southeastern United States are described.…”