Southern right whale (Eubalaena australis) population demographics at major calving ground Head of Bight, South Australia, 1991–2016

Abstract

1. Demographic parameters were estimated for southern right whales (SRWs), Eubalaena australis, using photo-identification (photo-ID) and count data collected during annual cliff-based surveys at the Head of the Great Australian Bight (HoB), South Australia between 1991 and 2016. Photo-ID and count data were contributed from the annual aerial surveys of the south-western population in Australia (1993Australia ( -2016. 2. The HoB photo-ID database included 1,186 non-calf individuals, with 459 reproductive females. HoB is an open population and represents a relative proportion (0.48-0.21) of the overall south-western population, which is decreasing with population growth.3. No change was detected in the growth rate at HoB over time and there was no significant difference when compared to the overall south-western population. The estimated mean rate of increase for all SRW was 3.2% (± 1.3) per annum and for females with a calf was 4.6% (± 1.7) per annum at HoB, compared to 5.5% (95% confidence interval (CI) 3.78, 7.36) and 6.01% (95% CI, 3.78, 7.36), respectively for the south-western population during the same period.4. The apparent mean calving interval was 3.3 years (SD = 0.78, ± 0.14, 95% CI; 1996-2016), and a significant increase to 4 years was observed since 2015. The apparent mean age at first parturition was 9.0 years. The minimum estimated age of the oldest whale was 50 and oldest lactating female 41 years old.5. The SRW demographic data provides information for monitoring recovery, population status, species conservation management and global comparative studies. There is a need to understand fluctuations in calving intervals, threats to the population and implications for species recovery.

Long-term stability in the circumpolar foraging range of a Southern Ocean predator between the eras of whaling and rapid climate change

“…In South Africa, a suspected climate-driven shift from high-latitude to mid-latitude foraging grounds ( 17 ) coincided with a decline in body condition ( 69 ) and calving rates ( 70 ). SRWs wintering in SW Australia have also experienced a decline in reproductive output coincident with latitudinal shifts in foraging grounds ( 71 ). In contrast, a large proportion of SRWs wintering in the Auckland Islands consistently forages in mid-latitudes near the subtropical front ( 24 ) and has the best body condition score of any right whale population ( 72 ) in addition to having a high population growth rate ( 73 ).…”

Swimming across the pond: First documented transatlantic crossing of a southern right whale

“…Although these long‐term SRW photo‐identification data sets have been revealing the steady recovery of the species since whaling ended, the last decade has seen some unprecedented changes. Most interestingly, coastal prevalence has started to fluctuate enormously, and calving intervals have increased in the populations calving off Argentina, South Africa, and Australia (Charlton, 2017; Marón et al, 2015; Vermeulen et al, 2019, 2020). Furthermore, additional research revealed that in the South African SRW population, maternal body condition decreased by around 23% over the past two decades (Vermeulen et al, 2023) concurrent with a shift in foraging behavior (van den Berg et al, 2021).…”

Evaluating short- to medium-term effects of implantable satellite tags on southern right whales Eubalaena australis

“…The research was undertaken to address several priority research questions identified in the Australian Conservation Management Plan for SRWs, specifically to better understand offshore distribution and migration pathways (DSEWPaC 2012, Mackay et al 2020). The population demographics of the south-western population are well understood, and long-term monitoring has been undertaken through aerial and cliff-based research since the early nineties (Charlton et al 2022, Smith et al 2022. The south-western Australian population has an estimated abundance of 2549 individuals (Smith et al 2022), and the observed mean calving interval is 3.9 yr (95% CI: 3.8, 4.1) (Charlton et al 2021).…”