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New lease of life for original lighthouse vents

15/05/2018

As part of the ongoing conservation of the Cape Bruny and Maatsuyker Island lighthouses, a team effort has been underway to restore the original bronze vents from the lighthouses' lantern rooms.More

Record visitor numbers at Highfield Historic Site

09/05/2018

Visitation numbers at Highfield Historic Site in Stanley have reached a record high, with 12,535 people visiting in the 12 months ending March 2018.More

Cradle Mountain shuttle bus tender awarded

08/05/2018

A new bus fleet featuring environmentally friendly technology and vehicles with improved accessibility and increased capacity will help to meet increasing visitor numbers following the awarding of the tender to McDermott Coaches.More

Orca

Orca (Photograph by Angela Anderson)
Orcas, or Killer Whales, are the largest member of the dolphin family. Larger males reach up to 10m and 4 tons. They are easily identifiable by their distinctive black, grey and white colours. They have a grey saddle patch just behind the dorsal fin which is often used in identification of individuals along with the shape and marks on the dorsal fin. The dorsal fin is wide and tall and curves backwards in the female and is larger (2m) and more upright and triangular in the male. The belly, lower jaw and underside of tail flukes are white and they have a white eye patch just above and behind the eye. They have a rounded head without a distinct beak. The pectoral fins are paddle shaped and the tail fluke is broad with a distinct notch.

Pods can range in size to upwards of several hundred, although in Australian waters most reports are of less than 10 made up of family groups which usually include 1-2 adult males and the rest being females and juveniles. Antarctica and Macquarie Island are key localities, however Tasmania has the highest concentration of reported sightings Australia-wide. They occur off Tasmania in all seasons and may be playful, leaping and tail slapping or travelling fast. They often occur around seal colonies.

General Information

Orcas live in closely bonded family groups and are active hunters of fish, penguins, seals, dolphins and whales in Australian and Antarctic waters. In the northern hemisphere they are divided into two groups – residents and transients (which act more like those seen off Australia). Residents form matrilineal groups that can consist of three or more generations which spend their entire lives together. Groups are quite vocal when they feed on salmon so do not need the stealth of transient orcas which are marine mammal hunters. Orcas can live up to 90 years and generally calve about every 5 years once they reach sexual maturity. New born calves are around 2.6m in length and most are weaned by 2 years.

Stranding Information

Distribution map of sightings and strandings (click to enlarge)
Because of the incredibly strong bonds within Orca groups they are at risk of mass stranding if one gets into trouble. However they are also very familiar with coast lines unlike the oceanic Pilot and Sperm whales and are often able to get themselves out of trouble. They are quite agile and often stalk seals by beaching and then refloating themselves. 

Most Tasmanian records are of single dead animals found washed ashore but there has been at least one recorded mass stranding of 9 animals and there are other examples of mass strandings of Orcas off New Zealand and Australia. Orcas are believed to be responsible for panicking other marine mammals into mass stranding off Tasmania including groups of Common Dolphins, Bottle-nosed Dolphins and Pilot Whales.