WHALES AND DOLPHINS
What is the difference between dolphins and whales?
There is a difference between what we call a whale and what biologically is a whale. We tend to use whale for larger mammals living in the sea. Whales have baleen whereas dolphins have teeth. Killer whales for instance therefore are technically dolphins.
What do they eat?
Dolphins feed on most kinds of fish, including mullet, whiting, snapper, tuna, bream and invertebrates such as squid.
How do they sleep?
Dolphins sleep on the surface with only the blow hole exposed. Dolphins are 'conscious' breathers, which means that they have to be awake or semi-conscious to breathe, otherwise they would drown.
They doze for a few minutes at a time, and their blow hole periodically opens and closes by reflex action.
They sleep in a semi-conscious state, resting one side of the brain for a short time then swapping over. This technique also allows them to be aware of any dangers.
How deep can dolphins dive?
Bottlenose dolphins can dive to depths of 21 metres and even to 30 metres. Risso's dolphins can dive to over 1000 metres.
Why do they jump?
There are four probable reasons that dolphins jump: either to play, for communication with other dolphins, to get rid of parasites, or to get a better view over the water.
Do they migrate?
Some species of dolphins migrate. Some species travel hundreds of kilometres in circular territory, probably for food.
What is their gestation period?
Gestation lasts for 10 to 12 months.
How long do calves stay with their mothers?
Calves stay with their mothers up to five years or longer. Mothers are very protective and keep the calf at their side at all times during this period.
What do their sounds mean?
Dolphins use sound (i.e. sonar or echo-location) to find objects and hunt for fish. These sounds are of high frequency and send out at a rate of several hundred per second.
The sounds bounce off objects in the water and are picked up by special tissue in the lower jaw of the dolphin which conducts the echo through to the inner ear.
This allows dolphins to identify objects without having to touch them. Dolphins also sometimes use their sonar to stun fish. They also use sound to communicate with one another.
How long can dolphins stay under water?
For periods of up to 1 hour, although five minutes is usually the average.
Can we see dolphins even when the sea is rough?
No, we cannot since dolphins usually avoid the surface when the sea is rough.
Do dolphins look after their sick?
They are known for doing so, although this behaviour has rarely been observed in the wild. Dolphins stay underneath and at the sides of the sick and by doing so keep them close to the surface so that they can breathe.
However, they do give up after some time. Dolphins have also been observed swimming away from another dolphin entangled in a net.
How intelligent are dolphins?
Since no one has come up with a method to successfully rate the intelligence of a human being, measuring the intelligence of other species has proven difficult if not impossible.
The evaluation of dolphins' intelligence is especially difficult, because they are adjusted to an entirely different medium, i.e. water. However, we can say that dolphins are fast learners and are able to generalise and learn sign language.
Are whales local or migratory?
Most whales are migratory and travel to the poles in the summer and back to warm temperate waters in winter. Some populations are resident though.
Are whales and dolphins happy in captivity?
No, not at all. In captivity, the average age for dolphins is 6 years. They tend to develop disturbed behavioural patterns too. Some countries, for example Britain. have given up keeping dolphins in zoos.
Can you feed dolphins and whales?
No, you should not. Feeding them will change their food behaviour and will have a detrimental effect on the marine life in general. If you feed dolphins or whales, you interrupt the natural food chain.
How long is the gestation period for whales?
It is between 10 to 13 months. Whales give birth to a calf every 2 to 3 years.
How long is their lactation period?
The calf is fed for 3 to 9 months.
How many calves do whales have?
Whales gives birth to one calf at a time.
How long do whales stay underwater?
They mostly stay underwater for 3 to 8 minutes. However, longer periods of up to 30 minutes have been recorded.
Can whales and dolphins communicate across species?
They understand basic elements of other dolphin or whale species behaviour, some to the extent that they interbreed like rough toothed and bottlenose dolphins.
Are whales and dolphins aggressive and dangerous?
Most dolphin and whale species are peaceful and rather shy. So far humans have proven to be of greater danger to whales and dolphins than the other way round.
However, some species like killer whales and pygmy killer whales can become aggressive. They are much less aggressive than their names imply though. If you go diving with whales, the danger is mostly because of their size. They might harm you without intending to do so.
Why do whales strand?
There are different theories on this issue. The most recent evidence suggests that whales strand if their hearing is impaired by loud noise which can be caused by a Navy's sonar systems for instance.
Why are killer whales called killer whales?
They are called killer whales due to the fact that they feed largely on warm blooded prey. They hunt even whales occasionally, therefore the name "killer (of) whales".
Why are sperm whales called sperm whales?
Sperm whales were hunted for spermacetes, a substance found in their heads which was used to the production of perfumes, candles and ointments.
How well do whales and dolphins hear and see under water?
Whales and dolphins hear very well underwater, though not in air. A human being's hearing ranges from 40 Hz to 20 kHz. Dolphins use very high sounds for echolocation, so they can hear sounds as high as 150 kHz. Low sounds travel very far underwater, so whales can hear up to 20 Hz.
Their sight, however, is not very good, as it is not very important underwater. In deeper waters there is darkness. Dolphins and whales, therefore, navigate by their hearing instead of their sight.
How can we distinguish a male whale from a female?
At sea it is difficult to distinguish the two. Among baleen whales, females tend to be larger than males. Toothed whales males tend to be larger. They might also have other distinguishing features such as larger melons, larger dorsal fins or distinctive teeth.
Watching wild dolphins is a thrilling way to start the day and if you are lucky you may even come across one of the many species of whales that can be found just a few kilometres from Muscat's rugged coast.