Mammals > Resources

Cetacean FAQs

Three groups of mammals which have adapted to life in the water include the cetaceans (whales, dolphins and porpoises), sirenians (dugongs and manatees) and pinnipeds (seals, sea lions and walruses). However, it is the cetaceans that are the most specialised in the aquatic environment and for a long time even the most basic aspects of their biology remained a mystery. With recent advances in technology information such as the number of species worldwide, their evolutionary relationships, distribution, movement patterns, diet and adaptations are increasingly coming to light.

• How are whales classified?
• What is the difference between a whale, dolphin and porpoise?
• How many cetacean species are there in Australia and where can I get information about them?
• What features should I look for to identify a whale or dolphin?
• What do I do if I find a stranded cetacean?
• How do cetaceans sleep?
• How deep can whales dive?
• What do cetaceans eat?
• How do cetaceans use sound to see?
• What are the closest living relatives of cetaceans?
• Why do whales breach?
• How do you age cetaceans and how long do they live?

How are whales classified?

Whales are mammals. They are warm blooded, breath air through lungs and give birth to live young that are suckled on milk secreted from the mother's mammary glands. Many of the features we associate with other mammals have been modified or lost during the long process of evolution from land dwelling ancestors and they have become superbly adapted to life in oceans, seas and rivers.

Whales, dolphins and porpoises, collectively known as 'cetaceans' (Order Cetacea) are divided into two groups, the toothed whales or odontocetes (suborder Odontoceti) and the baleen whales or mysticetes (suborder Mysteceti). The toothed whales (around 72 species worldwide at present) generally feed on larger food items such as fish or squid and include groups such as the river dolphins, dolphins, porpoises, beluga, narwhal, Sperm Whale, pygmy sperm whales and beaked whales. The baleen whales (around 13 species worldwide) feed by filtering seawater to trap food such as planktonic invertebrates (e.g. krill), copepods, amphipods and small fish in the baleen plates attached to their upper jaws. They differ from the toothed whales in generally being larger, having baleen instead of teeth and having paired nostrils. The mysteceti include species such as the Gray Whale, Right Whales, Pygmy Right Whale and the 'rorquals' (a group that includes the Blue, Fin, minkes, Sei, Bryde's and Humpback Whales).

What is the difference between a whale, dolphin and porpoise?

The terms dolphin, porpoise and whale are confusing and do not relate well to the scientific classification of cetaceans. In general, whales are the largest cetaceans followed by dolphins and then porpoises. However, some 'whales' such as the Pilot Whale and Killer Whales are classified in the same family as dolphins (Family Delphinidae). The term 'porpoise' is sometimes used to refer to dolphins although it is now generally agreed that porpoise refers to toothed cetaceans with spade-like teeth and no beak belonging to the Family Phocoenidae (includes six species, one of which occurs in Australia).

How many cetacean species are there in Australia and where can I get information about them?

At present there are around 44 species recorded from Australia, 35 of these are toothed whales and 9 are baleen whales. Of the toothed whales, 19 species are from the family Delphinidae (including dolphins, pilot whales and killer whales) and 12 are from the family Ziphiidae (beaked whales). Also included are the Pygmy Sperm Whale, Dwarf Sperm Whale, Sperm Whale and Spectacled Porpoise. The baleen whales include the Southern Right Whale, Pygmy Right Whale and seven species of rorquals (a group characterised by the presence of long folds of skin behind and below the mouth).The number of cetacean species recognised worldwide and in Australia is constantly changing as the results of ongoing morphological and molecular studies become available.

The most up to date account of cetaceans recorded from Australia is in A Field Guide to the Mammals of Australia by Peter Menkhorst. Other useful guides include Whales and Dolphins of New Zealand and Australia by Alan Baker and Dugongs, whales and seals, a guide to the sea mammals of Australasia by Bryden, Marsh and Shaugnessy. Guides covering species found in other parts of the world as well as Australia are the Eyewitness Handbook Whales, Dolphins and Porpoises, the visual guide to all the world's cetaceans by Mark Carwardine, the Reader's Digest Whales, Dolphins and Porpoises by Carwardine, Hoyt, Fordyce and Gill and National Audubon Society Guide to Marine Mammals of the World.

What features should I look for to identify a whale or dolphin?

A few key points to note when attempting identification are:

1. Length of the animal
2. Colour, including any distinctive markings
3. Presence or absence of a dorsal fin, its position, shape and colour
4. Head shape (type of snout if any)
5. Tail fluke shape and markings
6. Characteristics of the 'blow' (e.g. shape, height )
7. Distinctive behaviour such as breaching, spinning
8. If in a group, the number of animals present
9. Type of habitat (coastal, river, deep ocean)
10. Geographic location.

Many of these features will be relatively easy to record if the cetacean has stranded alive or dead on a beach.Identifying cetaceans at sea is often extremely challenging and most species seen at sea only appear for a short period or only a small part of them will be visible at any one time. Compounding this problem is the fact that some species are difficult to tell apart without a series of detailed skull or body measurements. These problems aside, certain features will allow identification particularly if recorded along with a sketch or even photograph. The guides mentioned above provide detailed guidelines and illustrations that will assist in identification of cetaceans.

What do I do if I find a stranded cetacean?

If you find a stranded cetacean first determine if it is still alive by examining the eyes and watching for breathing. If the animal is dead, contact the local National Parks and Wildlife Office (NPWS) and they will record important information, take samples and make arrangements for it to be removed to a burial site or arrange for it to be collected by the Australian Museum.

If the animal is alive contact the nearest National Parks and Wildlife Service office or phone the Organisation for the Rescue and Research of Cetaceans in Australia Inc.(ORRCA) hotline (ph 02 9415-3333) and they will determine the best course of action. The ORRCA website has information on how to help a stranded whale at http://orrca.org.au

If it is going to be sometime before expert assistance arrives to a live stranding it is important to keep the animals skin moist, prove shade if possible, keep flippers and flukes cool, make little noise, keep bystanders at a distance and try to keep the animal upright (if necessary by digging away sand from around the animal to make way for flippers).

A range of whale and dolphin species strand along the New South Wales coast every year, most are as single animals or a female and calf. Many of these are animals that have died at sea and washed ashore, although sometimes a sick or injured animal will also come in to shore and die shortly afterwards. On other occasions the animal is alive and can be successfully returned to sea with some help. Strandings represent an important opportunity to learn more about the biology of cetaceans and it is important to contact authorities if you find one, even if it is a common species.

How do cetaceans sleep?

Cetaceans sleep by floating at the surface of the sea with their blowholes exposed, some species rest during the day and others at night. Sleeping cetaceans may either lie motionless or move their tails slightly, breathing rate is reduced and their eyes close, although they may open from time to time as the animal takes short naps. At least one species, the Sperm Whale, appears to sleep quite soundly given that ships have been known to collide with these sleeping giants. Unlike other mammals where breathing is involuntary, cetacean breathing is under voluntary control and the blowhole will close if an animal becomes unconscious. This prevents drowning, but can lead to suffocation unless the animal is held at the surface until it recovers consciousness. Interestingly, dolphins have been recorded supporting an unconscious group member in this manner.

How deep can whales dive?

The longest and deepest dives have been recorded for the Sperm Whale and bottlenose whales (Hyperoodon spp), the former having been recorded diving to 2 000m and staying underwater for up to 2 hours and 18 minutes. Some evidence suggests that Sperm Whales may even dive as deep as 3 000m to feed on bottom dwelling squid and other prey. Baleen whales tend to remain within 300m of the surface when feeding and rarely dive for more than about 40 minutes. Most dolphins also remain relatively close to the surface and dive for only short periods.

What do cetaceans eat?

The large baleen whales (mysticetes) obtain their food by filter feeding using comb-like baleen plates that grow from the roof of the mouth. Prey is captured either by gulping large amounts of seawater and forcing it across the plates thereby trapping small food items, or by 'skimming' across the surface of the water and then removing trapped food with the tongue. Items such as krill, (shrimp-like crustaceans), copepods, amphipods, molluscs, polychaete worms, other planktonic invertebrates and schooling fish make up most of the diet of the baleen whales. The toothed whales (odontocetes) hunt and eat a wider range of larger food items including fish, squid, octopus, molluscs and polychaete worms. Some species, such as the Killer Whale eat other cetaceans, seals and sea otters.

How do cetaceans use sound to 'see'?

Cetaceans often live in environments where there is little light, such as the deep ocean or the turbid waters of rivers. The toothed whales and dolphins (odontocetes) have developed senses other than sight to help them navigate and hunt for food. Like bats, the toothed whales and dolphins emit intense, short pulses of generally high frequency sound and use the returning echo to determine the size, position and distance of various objects (known as 'echolocation'). In the toothed whales and dolphins these sounds are produced in the soft tissues of the nasal passages near to the blowhole and transmitted by a large fatty structure (the melon) on the forehead. The large baleen whales are not known to use echolocation in the same way as the toothed whales, relying more on sight to locate food. However, they can make very loud low frequency sounds that travel long distances (typically about 30 km for Blue Whales) that may be used for detecting large scale oceanic features.

What are the closest living relatives of cetaceans?

Because cetaceans are so different from any land mammal it has been very difficult to determine their precise origins. Recent fossil discoveries and molecular studies are shedding more light on the origins and evolution of cetaceans. Morphological studies indicate that cetaceans are most closely related to either the even-toed ungulates (Artyodactyls such as deer, antelope, pigs, hippopotamus) or odd-toed ungulates (Perissodactyls such as horses, tapirs and rhinocerus). Molecular studies indicate that hippopotamuses are the nearest living relatives of cetaceans.

Why do whales breach?

When a cetacean launches itself into the air, head first and then lands back in the water with a splash, this is known as 'breaching'. Most species are known to breach at some time. The smaller dolphins are capable of complex twists and turns whereas some of the larger baleen whales may propel up to two thirds of their body out of the water and land either on their backs, sides or belly. Some species breach many times in a row and Humpbacks, renowned for breaching, may do so hundreds of times in a single bout.

The exact function of breaching is not known although a range explanations have been suggested including signalling, courtship display, a means of herding fish, displaying strength, dislodging parasites, getting a better look at boats or even just for the fun of it.

How do you age cetaceans and how long do they live?

It is possible to estimate the age of cetaceans using a number of methods. Toothed whales can be aged by cross sectioning their teeth and counting the number of layers (each layer generally corresponds to a year). Baleen whales can be aged in a similar way by examining the growth rings in their waxy ear plugs. More recently photographic identification and marking techniques have been used to estimate ages and lifespans of particular cetacean species or individual animals.

In general, the larger cetaceans live longer than the smaller ones. Sperm Whales are known to live up to around 60 years and some Bottlenose Dolphins are known to live up to around 50 years in the wild. The smaller Harbour Porpoise is known to live to around 15 years of age.

Copyright © Australian Museum, 2003