On the occasion of the 25th edition of Dolphin Address 2003 the entry of our correspondent in Berlin, Verena Dommage here follows. She reacts with clarifying info to Dolphin Address nr. 19. The program quoted is called 'Wonderquest' and the question is answered by April Holladay.
Question: 'What do whales, porpoises, dolphins, manatees and other sea-dwelling mammals drink?'
Answer: 'Sea mammals mostly get their water from the food they eat. They break down carbohydrates and fat using oxygen to form water, carbon dioxide, and energy (a process called metabolism).
People have seen seals, sea lions, common dolphins and sea otters drink sea water on occasion. When they do, they rid their bodies of the extra salt by passing salty urine- up to 2,5 times saltier than seawater and 7 or 8 times saltier then blood.
Normally, though, fish-eating marine mammals have no extra salt to eliminate since the fish salt content is the same as their own blood. A study of Californian sea lions shows that these animals, feeding on fish, can live without any fresh water at all.
'Marine mammals can swim into fresh water habitats without any real complications (unlike most species of salt-water fish), but there is no evidence that they do so just to get a drink,' says Dave Rugh, wildlife biologist in Seattle.
Manatees (a plant eater) will drink from a garden hose left out along the brackish waterways in Florida. Some seals eat snow to get fresh water.
'For most whales and dolphins, however, we simply do not know how they get their water, because it is difficult to observe these animals', says Robert Kenney, marine biologist from Rhode Island.
'Their mouths are sometimes open when not eating,' Rugh says, 'but it is not evident how often they swallow sea water. (so far April Holladay)
This morning I saw for the first time that Dusty ate a fish, and a large one too. It was about as big as the salmon she brought me in the beginning of July, but the scales seemed coarser (the head was already inside), so I think it was a bass. She clearly had to make an effort and she did not swim as much away from me as she went in deep. Each time I saw the fish go in further, until only the tail was sticking out. Just after that she came alongside as of old for a cuddle. It is only later I realized I should have invited her for a pint in the pub.