Monitoring the recovery of the southern right whale in South African waters ...
Annual photographic surveys of right whale cow-calf pairs on the south coast of South Africa since 1979 have resulted in 2 270 resightings of 1 070 individual cows with calves. Observed calving intervals ranged from 2 to 23 years, with a principal mode at 3 years and secondary modes at 6 and 9 years...
| Main Authors: | , , |
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| Format: | Report |
| Language: | unknown |
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University of Cape Town
2023
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| Online Access: | https://dx.doi.org/10.25375/uct.24545908.v1 https://zivahub.uct.ac.za/articles/report/Monitoring_the_recovery_of_the_southern_right_whale_in_South_African_waters/24545908/1 |
| Summary: | Annual photographic surveys of right whale cow-calf pairs on the south coast of South Africa since 1979 have resulted in 2 270 resightings of 1 070 individual cows with calves. Observed calving intervals ranged from 2 to 23 years, with a principal mode at 3 years and secondary modes at 6 and 9 years, but these made no allowance for missed calvings. Using the model of Payne et al. (1990), a maximum calving interval of 5 years produces the most appropriate fit to the data, giving a mean calving interval of 3.16 years with a 95 % confidence interval of (3.14, 3.19). The same model produces an estimate for adult female survival rate of 0.990 with a 95% confidence interval of (0.985, 0.994). The Payne et al. (1990) model is extended to incorporate information on the observed ages of first reproduction of grey-blazed calves, which are known to be female. This allows the estimation of first parturition (median 7.67 years with 95% confidence interval (7.19, 8.16)). First year survival rate was estimated as 0.737 ... |
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