Category: Dolphin FAQ

Most dolphins live in the ocean and the ocean water is too salty for them to drink. If they would drink sea water, they would actually use more water trying to get rid of the salt than they drank in the first place. Most of their water they get from their food (fish and squid). Also, when they metabolize (burn) their fat, water is released in the process. Their kidneys are also adapted to retaining as much water as possible.

There are a number of dolphin species that live in fresh water. They all belong to the river dolphin families. These are: the Platanistidae (Ganges and Indus river dolphins), the Iniidae (the boto or Amazon river dolphin) and the Pontoporiidae (the baiji and the franciscana). There is one species that can be found both in fresh water (the Amazon river) and in coastal sea waters: the tucuxi (Sotalia fluviatilis). In general, salt water species don't do well in fresh water.

The dolphin's fast cruising speed (a travelling speed they can maintain for quite a while) is about 3-3.5 m/s (6-7 knots, 11-12.5 km/hr). They can reach speeds of up to 4.6 m/s (9.3 knots, 16.5 km/hr) while travelling in this fashion. When they move faster, they will start jumping clear of the water (porpoising). They are actually saving energy by jumping. When chased by a speedboat, dolphins have been clocked at speeds of 7.3 m/s (14.6 knots, 26.3 km/hr), which they maintained for about 1500 meters, leaping constantly.

The deepest dive ever recorded for a bottlenose dolphin was a 300 meters (990 feet). This was accomplished by Tuffy, a dolphin trained by the US Navy. Most likely dolphins do not dive very deep, though. Many bottlenose dolphins live in fairly shallow water. In the Sarasota Bay area, the dolphins spend a considarable time in waters that are less than 2 meters (7 feet) deep. Other whale and dolphin species are able to dive to much greater depths even.

If a single whale or dolphin strands, it usually is a very sick (and exhausted) animal. Such an animal often has some infections (pneumonia is almost always one of them) and a lot of parasites (worms in the nasal passages are very common). Sometimes these animals can be rehabilitated, but often they are so sick they won't make it. Some species of whales and dolphins occassionally strand in groups. A stranding of 2 or more animals is usually called a mass stranding.

The maximum age for bottlenose dolphins is between 40 and 50 years. The average age a dolphin can get (the life expectancy) can be calculated from the Annual Survival Rate (the percentage of animals alive at a certain point, that is still alive one year later). For the dolphin population in Sarasota Bay, the ASR has been measured to be about 0.961. This yields a life expectancy of about 25 years. For the population in the Indian/Banana River area, the ASR is between 0.908 and 0.931. This yields a life expectance between 10.3 and 14 years.

Bottlenose dolphins eat several kinds of fish (including mullet, mackerel, herring, cod) and squid. The compostion of the diet depends very much on what is available in the area they live in and also on the season.

To able to see colors, the retina must have at least 2 different kinds of cones, with different sensitivities. Most mammals have 2 types of cones: L-cones (sensitive to long-wavelength light, red to green) and S-cones (sentitive to short-wavelength light, blue to violet or near UV). Humans and some other primates have 3 types of cones, giving them a better color vision.

You may be aware that dogs have a hearing range well above that of human beings – they are capable of hearing high frequencies that humans simply are not able to hear. But, did you know that dolphins have a hearing range that far exceeds that of humans and even dogs? In fact, dolphins are able to hear, and to produce, some of the highest frequency sounds of all mammals. Let's put this into perspective. Humans have a hearing range of around 20 Hz to 20kHz.

Can dolphins kill or stun prey with loud sounds? It certainly seems that way if you believe following headlines: Dolphins' killer sonar confirmed from ABC Science Online February 2001. Killer clicks from New Scientist 1 January 2001. These are, of course, thrilling headlines and far more interesting than the contents of the research papers that they describe.