Cut off from the ocean by the natural catastrophe, the marine dolphins were forced to become entirely freshwater animals which now never venture as far as the tidal zone. In the process of adapting to the changed conditions some of their faculties have become atrophied and others amazingly highly developed due to the darkness of murky waters and fierce currents of the Indus. Loss of vision (Platanista is totally blind) has been compensated by an extremely efficient sonar system which enables the dolphins to locate and identify even minute objects. The flipper has evolved as an organ of touch. Safety in running water is ensured by ceaseless activity interrupted only by sleep pauses, not more than a few seconds long.
Until recently, the dolphin was considered almost extinct, the main reason for its decline being the barrages which were built across the Indus by the British to irrigate the Sind desert. This complicated system of irrigation, which made the desert bloom, also had the effect of isolating the population of the Indus Dolphin between the barrages where, with the added pressure of hunting, they slowly disappeared.
When Pilleri came to investigate reports of the existence of the dolphin in 1974, he was only able to count a total of 150 individuals. As a result of this study the Indus Dolphin was included in the IUCN Red Data Book and the Government of Sind declared the stretch of the Indus between the Sukkur and Guddu Barrages a Reserve for the dolphin. Sind Wildlife Management Board in collaboration with IUCN/WWF and the Volkart Foundation, launched a research and protection programme in 1977 to identify the conservation requirements of this unique species. Although international funding ceased in 1980, the Government of Sind continues to run a conservation programme and latest count of the dolphin reveals a figure of 367 individuals.
One of the most interesting aspects of this dolphin (which is fairly primitive by cetacean standards) is the incredibly complex sonar system which has been developed as a compensation for the lack of vision. G. Pilleri explores the biological implications of such a step in evolutionary terms in his book “The Secrets of the Blind Dolphins.”
Pakistan Post Office is issuing a set of two special postage stamps on the blind ‘Indus Dolphin’ (Platanista indi) on the 24th April, 1982, of the denomination of 40 Paisa and Rs. 1/- to focus attention on the need to preserve one of this rare and unique species of the wildlife. This is the eighth set being issued in the series of wildlife stamps. Earlier issues on wildlife included a set of two stamps each on (i) Black Partridge (30 September, 1975) (ii) Urial (31 December, 1975) (iii) Peacock (31 March, 1976) (iv) lbex (12 July, 1976) (v) four stamps on pheasants, namely Monal, White-crested Kalij, Koklas and Cheer (17 June, 1979) (vi) one stamp on Green Turtle (20 June, 1981) and (vii) two stamps on Western Tragopan (15 September, 1981).