Monday, 13 October 2014

Delta dolphins

Dolphins have been spotted along the Dutch coast, something that had not happened for a long, long time. According to this website, dolphins disappeared from the Dutch delta after the closure dam in the Zuiderzee was constructed in 1932 and only after some accidental events in the 1940s and 2004, it took until now that the dolphins 'returned'. They were spotted near the southwest delta, close to the Westerschelde.

This is not some small fact, only of relevance to biologist or environmentalists. No - this means that the last piece of the puzzle has been found (and fits)! Because now, the Dutch delta finds itself among the ranks of a number of other dolphin-rich deltas: from the Amazon to the Irrawaddy, but mainly from the Ganges to the Mekong: the two other cases in our comparative research program.

A nice account of a researcher's interest in delta dolphins, something that made me actually notice the importance of the rediscovery of Dutch delta dolphins, is the novel written by Amitav Ghosh, the Hungry Tide. He describes the experiences of a researcher trying to locate the Irrawaddy dolphin, which is the name given to dolphins living in the estuarine environment in Southeast Asia, in the Sumdarbans of the Ganges. In his book, dolphins in the Ganges delta are the central figures around which the delta stories are told.

He describes the dolphin as a species that 'knows' how to deal with the tidal dynamics, both with ebb and high water, and both with fresh and saline water. At the same time it is put under pressure by human settlement in deltas. Traditional knowledge and 'hard science' come together when trying to discover the animals' habits. For many environmental protectionist, the dolphin is an 'indicator' of healthy and good functioning delta ecosystems; for others, a source of spiritual guidance; and for again others, of very little relevance and only a means to reach other ends.

Just to complete this theme - besides the Irriwaddy dolphin (orcealla brevirostris), Bangladesh is also home to the South Asian river dolphin (platanista gangetica): a much smaller cousin, living more (up to hundreds of kilometers inland, even in Nepal), with the habit of swimming sideways. In that way, the dolphin finds its way by touching the ground with one of its fins as a reference, because it can't see well.

Go, Flipper!

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