DOI: 10.5061/dryad.9s4mw6mth
title: Data from: The end of an era? Trends in abundance and reproduction of Australian southern right whales (<em>Eubalaena australis</em>) suggest failure to re-establish pre-whaling population size

description: The large-scale exploitation of whale populations in the whaling era led
 to the near extirpation of large whales all over the world. This must have
 had major repercussions for marine ecosystems globally. Consequent changes
 to those ecosystems and physical environments create uncertainty around
 whether present-day conditions are adequate to support full recovery of
 pre-whaling population sizes. Combined with potential effects of
 anthropogenic stressors, the future viability of exploited whale
 populations is questioned. This migrating species was left near extinction
 from whaling and has shown slow, yet steady, recovery in recent decades.
 Here, we collate abundance data from aerial surveys performed along the
 Australian coast between 1976-2024, covering 2250 km of coastal habitat,
 to study the recovery trajectory of Australian southern right whales
 (Eubalaena australis). We describe temporal trends in abundance,
 reproduction and growth of the western sub-population. Despite previously
 displaying exponential growth and a present population size residing far
 below pre-whaling levels, our study reveals that annual births have
 started declining since 2016, and annual abundances of unaccompanied
 individuals have dropped by 66%. Our results suggest the end of an era of
 this populations’ recovery, highlighting that an initial period of steady
 recovery does not guarantee successful re-establishment of previous
 abundances.
description: # Data from: 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 **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](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](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](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](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.