A photo-identification-based assessment model of southern right whales Eubalaena australis surveyed in South African waters, with a focus onrecent low counts of mothers with calves ...

• Main Authors: Brandão, A, Ross-Gillespie, A, Vermeulen, E, Butterworth, DS
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: Taylor & Francis 2023
• Subjects: Evolutionary Biology; FOS Biological sciences; 59999 Environmental Sciences not elsewhere classified; FOS Earth and related environmental sciences; Ecology; Sociology; FOS Sociology; 69999 Biological Sciences not elsewhere classified; Inorganic Chemistry; FOS Chemical sciences; Science Policy; Southern Right Whale
• Online Access: https://dx.doi.org/10.6084/m9.figshare.22657017.v1; https://tandf.figshare.com/articles/journal_contribution/A_photo-identification-based_assessment_model_of_southern_right_whales_i_Eubalaena_australis_i_surveyed_in_South_African_waters_with_a_focus_onrecent_low_counts_of_mothers_with_calves/22657017/1

Photo-identification data for southern right whale cow–calf pairs on the South African calving grounds provide one of the longest abundance time-series for any whale population worldwide. Following a very steady increase from a heavily depleted state, surveys since 2015 reflect many notably low counts. These data are analysed to investigate whether these low counts can be explained by changes in reproduction-related parameters. This necessitates a modification to an earlier reproduction model for these whales, fit to photo-identification data to allow for early abortions; hence, a whale pregnant one year can again be pregnant the next. This can account for an increase in calving intervals in a way that differs from a whale resting for another year or an increase in late-abortion probability. This modification was able to account for the low number of sightings of cow–calf pairs over the 2015 to 2020 period (excepting for 2018), though the estimated probability of sighting a cow–calf pair in 2018 is somewhat ...