Killer Whales are the largest member of the dolphin family and are recognisable by their distinctive black, white and grey coloration. The head is rounded, with no distinct beak. A white eye patch, or spot, is located just above and behind the eye. Just behind the dorsal fin is a grey saddle patch. The Killer Whale’s belly, lower jaw and the underside of the tail flukes are white. The rest of the body is black. The wide, tall dorsal fin is curved backwards in females and is more upright and triangular-shaped in males. The pectoral flippers are paddle-shaped. In addition to sexual size dimorphism, male Killer Whale appendages are disproportionately larger than in females. Adult male and female Killer Whales attain weights exceeding 4000 kg and 3100 kg, and lengths of 9.8 m and 8.5–9.2 m, respectively. Although groups of up to several hundred individuals have been observed, group size is usually less than 30, and several studies outside Australian waters have reported mean pod sizes of less than 10. Off southern Australia, group size can be up to 52 individuals, although most sightings report less than 10. Long-term studies in the north-western Pacific have shown that pod composition appears to remain consistent over time; about 20% are adult males, 40–50% adult females and 30–40% immatures and juveniles. A social hierarchy exists within the pod.
Killer Whale, Orca |
Government evidence of impact of climate change:
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Australian Government Department of Agriculture, Water and the Environment, Species Profile and Threats Database, Orcinus orca
Increasing ocean temperatures predicted by climate change scenarios could potentially decrease the extent of occurrence of the Killer Whale; because of warmer water extending southwards.
Killer Whales that are dependent on sea ice for foraging in Antarctica; may be especially vulnerable to changes in sea ice coverage due to climate change (Andrews et al. 2008).Little is known about reproduction in Australian Killer Whales; however; it is likely that they have a low reproductive rate; producing one offspring every several years (Ross 2006).