Document ID: chunk:federal_register_of_legislation:F2013L00289:body:0:p18
Version: federal_register_of_legislation:F2013L00289
Segment Type: other
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Character Range: 57259–60207

opportunistically in winter nursery areas where suitable prey densities occur52. Satellite tagging and stable isotope analysis show right whales off South Africa feed both at, and south of, the Sub-Tropical Front in both Sub-Antarctic and Polar Frontal zones1, 29 and in a high productivity coastal upwelling system26. Isotopic and genetic analysis has shown that southern right whales return to their maternal feeding grounds suggesting that they may have limited capacity to explore new feeding grounds98.

Southern right whales from Australian populations probably forage between about 40°S and 65°S, generally south of Australia3, 15, 72, 94. Feeding whales have been observed in the region of the Sub-Tropical Front 41–44°S in January65 and December15. In that region they mainly consume copepods, while at higher latitudes (south of 50°S) krill is the main prey item94. Coastal Australian waters are not generally used for feeding, but other parts of the Australian EEZ - where environmental conditions are suitable - may be used.

Right whales feed by surface skimming66 or shallow dives, trapping plankton on fine baleen fibres. In the northern hemisphere fine-scale foraging patterns of other right whale species are related to prey density and the vertical distribution of zooplankton20, 22, 105. Similar fine-scale foraging is likely for southern right whales, although this has not been observed or investigated to date.

Survivorship
As southern right whales have a long lifespan with a relatively low reproductive rate, adult mortality (particularly adult females) can have a significant effect on the overall population. Southern right whales have few natural predators, although calves, juveniles or weakened adults may be killed by sharks (principally great white sharks), which are common in some Australian calving grounds. Shark bite wounds are evident on all population classes (males, non-calving females, juveniles, sub-adults), though in adults these are confined to the flukes and are unlikely to cause death in healthy, mature individuals. Scars consistent with wounding by killer whales are evident on adult and juvenile whales, but not on calves. Southern right whales may be more vulnerable to killer whale attack in the open ocean, e.g. on migration or at higher latitudes where killer whales are more common16.

Adult southern right whales rarely strand, but small numbers of calves are regularly found dead or stranded near calving grounds. Neonatal mortality at the Head of Bight has been estimated to be at least 3 per cent during the first three months of life32. Poor environmental conditions can cause nutritional stress98 and may affect calf survivorship, but this has not been measured.

Mortality rates for adult southern right whales from the southwest Australian population are assumed to be low and survivorship high, given their recent consistent rate of population increase of approximately 6.8 per cent