N.B. We strongly urge anyone planning to use any of the data here, to read the methodology provided our open access research article and the accompanying Supporting Information file (links provided below).

This dataset accompanies research article:

Grundlehner, A., Smith, J.N., Bannister, J.L., Andrews-Goff, V., Brasier, M., Double, M.C. and Corney, S.P. (2025), The End of an Era? Trends in Abundance and Reproduction of Australian Southern Right Whales (Eubalaena australis) Suggest Failure to Re-Establish Pre-Whaling Population Size. Glob Change Biol, 31: e70218. https://doi.org/10.1111/gcb.70218

In the research article, we investigate the coastal abundance and reproductive success of the western Australian southern right whale (Eubalaena australis, SRW) population. We interpolate and assess trends in abundance, growth rate, population size and calving intervals from 1976 to 2024. The attached dataset contains all the curated dataset used for statistical analyses, as well as the temporal trends derived from the statistical models.

Species background

SRWs are a migratory baleen whale found in mid and high latitudes in the Southern Hemisphere. SRWs are a migratory baleen whale with a circumpolar distribution in the Southern Hemisphere between latitudes 20°S and 60°S (Kenney, 2018). Their migration is tightly linked to their seasonal reproduction. During the winter period, part of the populations migrates to coastal areas that are particularly important for females, who use the shallow coastal waters to gestate and nurse their young (Best et al., 2003; Carroll et al., 2011; Sprogis et al., 2024). Individuals other than mothers with their calf visit coastal regions too, but it is unsure what fraction of the population visits the coast these “unaccompanied individuals” (any adults not accompanied by a calf) represent. It is hypothesized they may be visiting coastal waters for mating, but yearlings, sexually immature, skip-breeding, post-lactation recovering, post-menopause individuals, and cows that still need to calf and/or had a failed pregnancy, may be included too (Best et al., 2003).

SRW cows are strongly dependent on acquiring sufficient body fat storage during summer, to recover from pregnancy and nursing, because SRWs are capital breeders that fast while nursing their calf. In healthy conditions, three-year calving intervals are considered the standard for SRWs, and females assumed to have their first offspring at the age of seven or eight (Bannister, 2001; Best, 1994, 2001; IWC, 2001). SRW breeding cycles include one year of gestation, one year largely spent nursing and one year of recovery allowing females to replenish body fat stores (Best 1994, 2001). Deviations from this interval is commonly linked to poor maternal body condition and limited food resources (IWC, 2013; Vermeulen et al., 2023). Failure to acquire sufficient body fat reserves causes failed pregnancies, reduced calf survival and longer calving intervals (Christiansen et al. 2018; Germishuizen, Vichi, and Vermeulen 2024; Leaper et al. 2006; Seyboth et al. 2016).

During winter, cow-calf pairs (SRW mothers with their young) reside almost exclusively in the shallow coastal waters within 1 km from the coast. Unaccompanied individuals are less bound to single aggregation areas than mothers with their calves and likely move around between aggregation areas. Further information in research article.

Background of the data

This dataset is compiled using a collection of sightings records of SRWs, which have been recorded during annual aerial survey monitoring programs between 1976 and 2024. During the surveys, a single engine aircraft flies parallel to the coastline, approximately one nautical mile off the coast at 1000 feet altitude. Human observers record SRW observations. Upon a SRW sighting, the search is interrupted for photo-identification purposes.

Initially, the surveys covered the coastline from Augusta to Israelite Bay (Western Australia), but over time the spatial extent of the surveys was extended east. Since 1993 the surveys were performed in its fullest extent, our study area in Australia covers the coastline from Cape Leeuwin (Augusta, Western Australia) to Ceduna (South Australia), approximately 2250 km of coastline. Until 2007, the study area was monitored at least three times a year, between July and October. Thereafter only one annual series of flights is performed during the peak abundance of cow-calf pairs that occurs mid-August to mid-September. The data presented is only based on information from survey flights performed during this peak abundance and is truncated to maximum SRW abundances per coastal segment per year.

Further information in research article.

Description of files and content

"GBC_SRW4TRANSECTS_MAX_PERKM.csv"

This file constains the data used for analyses in the article published in GBC. Note that this is a curated dataset and the coastal area indicated in column "transect"/"segment", has not always been flown in one continuous flight (e.g. sometimes a stop of multiple hours or at most one day was made about halfway, and the number of SRW observations from the two surveys were summed). The curation process is described in detail in the Supplementary Information file that is attached to the research article. This is necessary to maximise the spatiotemporal extent of the research presented. The data contains whale abundances (expressed per km coastline surveyed), observed on a focal 'segment' in a focal year. We distinguished the abundance of calves, adults, and unaccompanied individuals. We strongly urge anyone planning to use any of the data here, to read the methodology provided our open access research article and the accompanying Supporting Information file (links provided below), in order to understand the limitations of this dataset and prevent mis-use and mis-interpretation.

Columns:

• 'Year' represents Year of survey
• 'Segment' is the segment (coastal transect), note that all observations and model outputs are segment-specific.
• 'calf_100km' Maximum number of calfs (equals cow-calf pairs) per 100 km observed along surveyed segment in a given year.
• 'unacc_100km' Maximum number of unaccompanied individuals (all whales observed without a calf, except yearlings)  per 100 km observed along surveyed segment in a given year.

"UI_GAMMoutput_full.csv" and  "CC_GAMMoutput_full.csv"

These two files contain the output of the GAMMs presented in the paper. CC refers to calves (Cow-Calf pairs) and UI stands for unaccompanied individuals. These two files contain all the predicted values from the model. These predicted values are dependent of year of observation and coastal segment. These data files contain 'predicted values (Column Pred) (the abundance of either UI or CC pairs, expressed per surveyed km), with upper and lower confidence intervals (Columns SeLo; SeUp). Segment lengths are provided in the file too, for conversion back to count data.

Columns

• 'Segment' is the segment (coastal transect), note that all observations and model outputs are segment-specific.
• 'Year' represents Year of survey
• 'Pred' represents fitted model values (number of calfs per 100 km in focal year on focal transect)
• 'Pred'_CI_lo' represents lower limit of confidence interval of fitted model values (number of UI per 100 km in focal year on focal transect)
• 'Pred'_CI_up' represents upper limit of confidence interval of fitted model values (number of UI per 100 km in focal year on focal transect)

"UI_TotalPred.csv" and "CC_TotalPred_and_GrowthRates.csv"

These files contain the presented temporal trend (Figure 3 in article), which is in essence a summary of the data in "UI_GAMMoutput_full.csv" and*  "CC_GAMMoutput_full.csv".* In this file however, the fitted model is summarised per year, reconverted to count data and converted to an interpolated abundance trend covering the entire study area.  Again, CC containing the model output for calves (Cow-Calf pairs) and UI for unaccompanied individuals. The annual growth rates (CAGR) for CC, which are presented in the article are based on the fitted model, and therefore added to the simulated datasets. 

Columns

• 'Year' represents Year of survey
• 'MeanFit' represents the estimated number of SRWs (either UI or CC) throughout the entire study area in a given year
• 'MeanCI_lo' represents the lower confidence limit of the estimated number of SRWs (either UI or CC) throughout the entire study area in a given year
• 'MeanCI_up' represents the upper confidence limit of the estimated number of SRWs (either UI or CC) throughout the entire study area in a given year

Further information

Supplementary Information to the article in GBC can be found here: https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1111%2Fgcb.70218&file=gcb70218-sup-0001-DataS1.pdf

References cited

Bannister, John L. 2001. ‘Status of Southern Right Whales (Eubalaena Australis) off Australia’. Journal of Cetacean Research and Management 2:103–10.

Best, Peter B. 1994. ‘Seasonality of Reproduction and the Length of Gestation in Southern Right Whales Eubalaena Australis’. Journal of Zoology 232(2):175–89.

Best, Peter B. 2001. Right Whales: Worldwide Status. Vol. 2. International Whaling Commission.

Best, Peter B., C. R. Schaeff, and P. Palsbøll. 2003. ‘Composition and Possible Function of Social Groupings of Southern Right Whales in South African Waters’. Behaviour 140(11–12):1469–94. doi:https://doi.org/10.1163/156853903771980675.

Best, Peter, Schaeff, Desray Reeb, and Per Palsbøll. 2003. ‘Composition and Possible Function of Social Groupings of Southern Right Whales in South African Waters’. Behaviour 140(11–12):1469–94. doi:https://doi.org/10.1163/156853903771980675.

Carroll, Emma, N. Patenaude, A. Alexander, D. Steel, R. Harcourt, S. Childerhouse, S. Smith, J. Bannister, Rochelle Constantine, and C. Scott Baker. 2011. ‘Population Structure and Individual Movement of Southern Right Whales around New Zealand and Australia’. Marine Ecology Progress Series 432:257–68.

Christiansen, Fredrik, Fabien Vivier, Claire Charlton, Rhianne Ward, Alicia Amerson, Stephen Burnell, and Lars Bejder. 2018. ‘Maternal Body Size and Condition Determine Calf Growth Rates in Southern Right Whales’. Marine Ecology Progress Series 592:267–81.

Germishuizen, Matthew, Marcello Vichi, and Els Vermeulen. 2024. ‘Population Changes in a Southern Ocean Krill Predator Point towards Regional Antarctic Sea Ice Declines’. Scientific Reports 14(1):25820. doi:10.1038/s41598-024-74007-1.

International Whaling Commission. 2013. ‘Report of the IWC Workshop on the Assessment of Southern Right Whales’. Journal of Cetacean Research and Management 14:439–62.

IWC. 2001. ‘Report of the Workshop on the Comprehensive Assessment of Right Whales: A Worldwide Comparison’. Journal of Cetacean Research & Management (special issue).

Leaper, Russell, Justin Cooke, Phil Trathan, Keith Reid, Victoria Rowntree, and Roger Payne. 2006. ‘Global Climate Drives Southern Right Whale (Eubalaena Australis) Population Dynamics’. Biology Letters 2(2):289–92.

Seyboth, Elisa, Karina R. Groch, Luciano Dalla Rosa, Keith Reid, Paulo A. C. Flores, and Eduardo R. Secchi. 2016. ‘Southern Right Whale (Eubalaena Australis) Reproductive Success Is Influenced by Krill (Euphausia Superba) Density and Climate’. Scientific Reports 6(1):28205.

Sprogis, Kate, Rob Harcourt, Leena Riekkola, Simon Childerhouse, Virginia Andrews-Goff, and Emma Carroll. 2024. Western Australian Southern Right Whale Coastal and Offshore Movements.

Vermeulen, Els, Terriann Thavar, Maria Glarou, Andre Ganswindt, and Fredrik Christiansen. 2023. ‘Decadal Decline in Maternal Body Condition of a Southern Ocean Capital Breeder’. Scientific Reports 13(1):3228.