Young Marine Scientist - Dr Gerald Goeden: July 2013

Wednesday, 31 July 2013

Where Did Whales Come From?

Whales and dolphins belong to a group of animals called cetaceans. All cetaceans live in water today but their ancestors were land animals. The closest relative to today’s cetaceans is the hippopotamus. Whale ancestors left the land about 50 million years ago and became the baleen whales (plankton feeding) and toothed whales (fish and squid eaters) of today.

What did the early whales look like and how did they live?

The first fossils were found in the

United States

and were so different from modern whales that they were described as a reptile (dinosaur). Because of their size, they were named Basilosaurus, or king lizard. Many fossils were found with an average length of 18 metres and scientists believed that they may have reached 45 metres. Fossils have been found in Pakistan and

Egypt

and may have given rise to early worship of crocodile-like gods.

But they weren’t lizards!

We now know that the fossil Basilosaurus was a whale that probably hunted in shallow seas between 34 and 40 million years ago. It was about 18 metres long and the biggest animal on Earth at that time.

It had small paddle like hind fins that were left over (vestigial) from what were once legs. They were so small that the Basilosaurus probably swam more like a snake than a modern whale.

We can be very certain (look at the teeth) that Basilosaurus was an aggressive and dangerous predator. Careful examination of the skeleton suggests that Basilosaurus may not have been a long distance swimmer and probably could not dive to great depths. Its head and teeth are reminiscent of a crocodile’s and it may have hunted in a similar way; surprise attacks in shallow water or swimming down unfortunate prey.

Another 30 million years of evolution finds us sharing the planet with 81 species of whales from the metre long Hector’s dolphin to the Blue Whale, the largest animal to have ever lived on Earth.

Mother and calf of the Blue Whale

The Bottle Nose Dolphin is a whale too.

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Tuesday, 9 July 2013

DOLPHINS AND POLLUTION by Dr. Gerald Goeden

The famous Chinese White Dolphins are at home in the waters around Hong Kong but they live in a dangerous place. There has always been concern with the high speed shipping that travels the area. But shipping isn’t their only worry as these territorial animals are faced with rapidly decreasing water quality.

As the human population soars, the tiny island of Hong Kong spews its wastes into the sea. Industrial, agricultural, and domestic sewage are now the greatest threats to the Chinese White Dolphin. In the Pearl River Delta, about 190,000 tonnes of untreated sewage is pumped into the sea each day. The raw sewage and industrial pollutants affect the dolphins as well as the whole ecosystem.

Studies of dead Chinese White Dolphins reveal heavy metals, such as mercury, and organic materials including tributyltin (TBT), an anti-fouling agent, and organochlorines, such as PCBs and DDT. These poisons have entered the dolphins' food chain. Because dolphins and man enjoy the same foods, there is every reason to be concerned about both dolphin and human health.

Fishing also takes its toll as there are few Hong Kong laws about catching dolphins and even less enforcement. Incredibly, dolphins are considered trash fish and can be kept as by-catch to be eaten or used as bait.

The Chinese White Dolphin is found throughout Southeast Asia, and they range from South Africa to Australia. There are two subspecies, with Indonesia the dividing line between the Chinese and the Western subspecies.