Demographic parameters of southern right whales off South Africa

Abstract

Aerial counts of right whale cow-calf pairs on the south coast of South Africa between 1971 and 1998 indicate an annual instantaneouspopulation increase rate of 0.068 per year (SE = 0.004) over this period. Annual photographic surveys since 1979 have resulted in 901resightings of 550 individual cows. Observed calving intervals ranged from 2-15 years, with a principal mode at 3 years and secondarymodes at 6, 9 and 12 years, but these make no allowance for missed calvings. Using the model of Payne et al. (1990), a maximum calvinginterval of 5 years produces the best fit to the data giving a mean calving interval of 3.12 years (95% confidence interval: 3.07, 3.17). Thesame model produces an estimate for adult female survival rate of 0.983 (95% CI: 0.972, 0.994). The Payne et al. (1990) model is extendedto incorporate information on the observed ages of first reproduction of grey-blazed calves, which are known to be female. This allows theestimation of age at first parturition (median 7.88 years 95% CI 7.17, 9.29). Updates of estimates and confidence intervals for the otherdemographic parameters are: adult female survival rate 0.986 (0.976, 0.999); first year survival rate 0.913 (0.601, 0.994) and instantaneouspopulation increase rate 0.071 (0.059, 0.082). These biological parameter estimates are shown to be compatible with the observed increaserate of the population without the need to postulate immigration.

Half a century of sightings data of southern right whales in Mar del Plata (Buenos Aires, Argentina)

“…To research the recovery of commercially overexploited species such as the SRW, it is essential to carry out studies both in space and time, not only in breeding areas, but also throughout their entire geographic range (Payne et al, 1990;Cooke et al, 2001 SRW sightings in MDP have increased gradually since 1970 to the present. Over the last decades, sighting records in different sites are indicative of the growth of the main South Atlantic breeding populations (Argentina, Brazil, South Africa and Australia), after severe depletion by commercial whaling (Townsend, 1935;Bannister, 2001;Best et al, 2001;Cooke et al, 2001;Richards, 2009;Crespo et al, 2019). Moreover, during the last decade, SRW breeding pods and non-social active groups have been increasing in the Golfo San Matías (Northern Patagonia), as it is a suitable habitat for social and reproductive activities (Vermeulen et al, 2012;Vermeulen, 2013;Arias et al, 2015;2017).…”

“…Towards the end of the 20th century, SRW populations in Argentina, Brazil, South Africa and Australia have shown signs of recovery, doubling over a period of 10–12 years (Bannister, 2001; Best et al ., 2001; Cooke et al ., 2001; Crespo et al ., 2015; Groch, 2018). Since the 1970s, the population that breeds in PV (Argentina) grew at a rate of 6.9% per year (Cooke et al ., 2001; Crespo et al ., 2014), and between 1999 and 2015, although it also grew, it did so at lower rates (Crespo et al ., 2019).…”

Decadal shift in foraging strategy of a migratory southern ocean predator

“…SRWs show migratory fidelity to destinations, with long‐term photo‐identification and genotype studies showing philopatry to natal wintering grounds (i.e. Bannister, 2001; Best, 1990; Best et al, 2001; Carroll et al, 2016; Patenaude & Baker, 2001; Payne, 1986). Furthermore, correlations between isotopic profiles (δ 13 C and δ 15 N), indicative of summer foraging grounds, and maternally inherited mitochondrial DNA haplotypes support the hypothesis that SRW calves learn annual summer foraging destinations from their mothers during a prolonged period of parental care (Carroll et al, 2015; Valenzuela et al, 2009).…”

“…SRWs show migratory fidelity to destinations, with long-term photo-identification and genotype studies showing philopatry to natal wintering grounds (i.e. Bannister, 2001;Best, 1990;Best et al, 2001;Carroll et al, 2016;Patenaude & Baker, 2001;Payne, 1986).…”

The Falkland Islands (Malvinas) as sub-Antarctic foraging, migratory and wintering habitat for southern right whales

“…In recent decades, evidence of increasing population size (doubling times of 10-12 years) has been provided by long-term studies at several of the core winter breeding grounds in the South-west Atlantic (Uruguay, Argentina and Brazil: Payne et al, 1990;Cooke et al, 2001), South-east Atlantic (South Africa and Namibia: Best et al, 2001;Brandão et al, 2013), Australia (Bannister et al, 2016) and the South-west Pacific (New Zealand; Carroll et al, 2013). While the global population in 2009 (13,600 individuals: IWC, 2013) was still significantly below the estimated pre-exploitation size of 55,000 to 75,000 animals (IWC, 2001), the steady signs of recovery documented worldwide have led to the species recently being allocated a status of Least Concern by the International Union for Conservation of Nature (Cooke & Zerbini, 2018).…”