Sperm whales
Sperm whales, Physeter macrocephalus, are the largest of all odontocetes and among the deepest diving of all cetaceans - they are known to dive over 1000 metres and they can stay underwater for over an hour at a time. They are best known through the sperm whale character ‘Moby Dick’ in Herman Melville’s story of the same name.
Sperm whales have a unique appearance with a massive blunt, squared off head that can be up to 7 metres long (or one-third the total body length) and a relatively small underslung jaw. Adult males can grow up to between 15 to 18 metres long and weigh 35 tonnes while females can grow to 11 metres long and weigh up to 14 tonnes.
Sperm whales have a single blowhole on the left side of their head and it sits facing forward causing their bushy blow to project forwards rather than straight up in the air. Their bodies have a wrinkled and shriveled appearance especially behind the head.
Sperm whales mostly eat deep water squid but also feed on fish, skate and octopus. A sperm whale can eat a tonne of food a day.
They have a cosmopolitan distribution but male sperm whales are found mostly in higher latitudes. These males sometimes migrate to lower latitudes, but only the largest males seem to migrate to the equatorial breeding grounds. Females, calves, and juveniles remain in the warmer tropical and sub-tropical waters.
Despite being widely hunted during the 19th and early 20th centuries, sperm whale populations remain quite healthy, especially in the southern oceans. Sperm whales are one of the more common stranding species on the coasts of NSW.
Pygmy sperm whale
The pygmy sperm whale, Kogia breviceps, is amongst the smallest of all whales; they are about 1.2 metres at birth, growing to around 4 metres at maturity. Adults weigh about 400 kilograms.
Pygmy sperm whales are found in the temperate waters of the Atlantic, Pacific and Indian Oceans. They have 12 to 16 sharp pairs of teeth in the lower jaw and feed on squid, octopus, shrimp, fish and crab.
Pygmy sperm whales are found singly or in groups of 2 to 3 individuals. However, they are rarely sighted at sea, so most of what we know about this species comes from stranded animals. Pygmy sperm whales are also one of the most commonly stranded species in NSW.
Bryde’s whale
Bryde’s whales (pronounced BROO-duhz), Balaenoptera brydei, named for a Norwegian whaling entrepreneur nearly a century ago, are baleen whales and rorquals. Rorquals – Norwegian for “furrowed whale” – have a series of longitudinal folds of skin running from below the mouth back to the navel.
Like other rorquals, Bryde’s whales are long and slender and have much more streamlined bodies than other large whales. Bryde's whales are dark grey in color on the dorsal side with a yellowish white ventral side. They have an average length of 12 metres, and the female is longer than the male. These whales can weigh 12 to 20 tonnes.
Bryde's whales are found in the Atlantic, Pacific, and Indian Oceans and off the coast of Ethiopia in warm temperate and sub-tropical waters. They are not migratory, but are known to move between inshore to offshore waters to follow food. They feed almost exclusively on:
- pelagic fish, such as pilchard, mackerel, herring, and anchovies
- pelagic crustaceans, such as shrimp, crabs, and lobsters
- cephalopods, such as octopus, squid, and cuttlefish.
Bryde's whales are quite opportunistic and will consume whatever shoaling prey is available. They often take advantage of the activities of other predators by swimming through and engulfing the fish they have herded. They are therefore frequently found in areas of high fish abundance, along with seabirds, seals, sharks, and other cetaceans.
It is not known how many of these whales inhabit Australian waters, but remarkably,a Bryde’s whale swam up the Manning River near Taree, in Northern NSW in 2004.
Beaked whales
There are about 20 different species of beaked whales in the world’s oceans. Their key distinguishing feature is the presence of a 'beak', somewhat similar to that of most dolphin species. Beaked whales are highly specialised to dive to great depths and remain submerged for prolonged periods—20 to 30 minutes is common, and 85 minute dives have been recorded.
Complex throat muscles help these animals suck their prey in, since they lack teeth for feeding. The teeth that some species of beaked whales do have are usually only used for fighting with other males.
These animals are so elusive that most of what we know about them comes from stranded animals.
In NSW, the strap-toothed beaked whale is one of the most commonly stranded species of beaked whales. Size-wise, beaked whales range from 4 to 13 metres in length and can weigh from 1 to 15 tonnes. Although the diet of beaked whales varies between and within species, squid are a key component of their overall diet.