Threats to southern right whale
Southern right whale showing side
fluke, Tautuku Peninsula
Killer whales may occasionally kill tohora. They are known to form hunting packs to take down larger whales but the success rate and frequency of this is largely unknown. Other potential predators are large sharks. Predation is likely to affect calves more than adults. It is possible that such attacks were one of the pressures leading to the evolution of right whales’ use of shallow coastal habitats for calving.
Southern right whale populations suffered dramatic losses due to whaling as they were deemed the “right” whales to catch: they were easy to approach, lived close to shore and provided large quantities of meat, oil and whalebone. Both Southern and Northern species came close to extinction and only the Southern is showing signs of recovery.
Present day threats include fishing, coastal development and human harassment. Incidental entanglement in fishing gear has been recorded, with both active fishing gear and lost “ghost” gear posing a threat.
Marine farms and coastal development results in the loss of habitat and can pose problems in terms of competition for both space and food.
Ship strike has also been reported, highlighting the importance of following the Marine Mammal Protection Regulations (1992) when in contact with cetaceans. A combination of these threats no doubt explains why tohora no longer occur in Wellington Harbour.