[In January 2003 I accompanied an expedition that was conducting a survey of river dolphins on a stretch of the Mekong River in Cambodia. The expedition was led by Isabel Beasley, who was then a PhD student specializing on Orcaella brevirostris: also known as the ‘Irrawaddy Dolphin’ this species is found in many Asian river systems and deltas. The journal I kept during the expedition will appear on this site as a continuous series of posts. This is part 9 of the series.]
Almost nothing is known of the parental and mating behaviour of orcaella. There are only speculations based on what is known of other species, particularly Tursiops which have extensively studied in Shark Bay in Australia.
By noon the sun was burning hot and Isabel decided to move on to the pavilion on the water at Kampi, just below the observation station. Here, in the shade, it is very tranquil, with cows grazing on the banks behind us and dolphins surfacing repeatedly in front of us, within a dozen yards.
At Chroy Banteay we briefly glimpsed a dolphin throwing up water. Isabel thinks this is done in two ways – one is by butting the water; the other is by actually spitting. Whenever Isabel has observed this, the dolphin spits repeatedly in a kind of semi-circle. Her ‘very preliminary’ hypothesis is that its creating a curtain of bubbles so that the fish will turn back and head directly towards it (the dolphin). Apparently fish are often reluctant to swim through bubbles. This makes more sense to me that the notion that they spit in order to herd (towards whom?).
