Manila Bay presented a sorry sight yesterday with hundreds of volunteers and fishermen using their boats and hands in the shallow waters to drive 200-300 dolphins back to the deep sea.

Their efforts paid off as they managed to guide more than 200 melon-head dolphins into deep waters, Filipino officials said.

The mammals might have been beached because of an underwater earthquake, which could have damaged their eardrums and disoriented them. Or, the pod could have been following a sick or injured leader, said Malcolm Sarmiento, director of the Bureau of Fisheries and Aquatic Resources.

Melon-head dolphins are considered a threatened species - meaning they are likely to become endangered.

Beached dolphins are not uncommon in the Philippine archipelago but rarely occur in such big numbers. Still it is more common to hear about or see beached whales than dolphins.

Both sea mammals have ears that are sensitive to sudden or large changes in pressure underwater, Sarmiento said.

The dolphins were spotted about 1.6 km off shore, swimming back and forth between Pilar and Orion townships in Bataan province.

Fishermen and villagers trooped to the beach and waded into the chest-deep water, clapping their hands and hitting the surface to drive the dolphins away. More than 20 boats with their engines shut guided the animals to the open sea.

"It's something unusual. It's the first time that such a large pod has entered the Manila Bay, and is acting strangely," Sarmiento said.

If a pod gets beached after following a sick leader, the animal has to be identified and removed out of sight of the rest of the dolphins so that the healthy ones can be prodded back to sea.

Alberto Venturina, the provincial veterinarian, said three dead dolphins found beached farther up north in Abucay township included two adult females, one of which was pregnant, and an infant male. The two adults had damaged eardrums.

Another beached dolphin was in the process of being rescued, he said.

Dolphins with injured eardrums become disoriented, cannot dive for food and are too weak to swim.

Questions:

1. Melon-head dolphins are considered a threatened species. What does that mean?

2. How did villagers and fishermen drive the dolphins back to deep water?

3. What may have caused the dolphins to be stranded?

Answers:

1. They are likely to be endangered.

2. They clapped their hands, hit the surface of the water and used boats to guide them.

3. They either followed a sick leader or their eardrums may have been damaged from an underwater earthquake.