The Gangetic dolphin’s “blindness” is actually an evolutionary adaptation to its turbid, sediment-heavy environment — not a handicap. Rivers like the Ganga are so murky that eyesight provides almost no advantage. Evolution eliminated the energy-expensive crystalline lens, leaving only vestigial light-sensitive eyes.

Instead, the dolphin developed extraordinarily sophisticated echolocation (biological sonar):

1. The dolphin emits ultrasonic clicks from the melon (fatty organ in the forehead)
2. These sound waves travel through the water and bounce off objects — fish, rocks, net structures
3. The returning echoes are detected through the lower jaw (which conducts vibrations to the inner ear)
4. The brain processes the echoes to create a 3D “acoustic image” of the surroundings

The precision is remarkable — Gangetic dolphins can distinguish individual fish species, detect their exact location and size, and track moving prey in complete darkness and turbid conditions. They also swim on their side when hunting near river bottoms — rotating 90 degrees, which also helps echolocation coverage of the sediment layer where prey hides.

This echolocation system is why noise pollution from boat engines and dredging is so dangerous for dolphins — it literally “blinds” them acoustically. ★

The cooperative fishing relationship between Irrawaddy dolphins and fishermen in Chilika Lake (and more famously in Myanmar’s Ayeyarwady River) is one of the most extraordinary human-wildlife interactions in the world. ★

How it works (observed in Chilika and Ayeyarwady):
1. Fishermen signal to the dolphins by knocking on their boat sides or splashing in specific rhythms
2. The dolphins respond by herding fish schools toward the fishermen’s boats and nets
3. As fish leap or scatter to avoid the dolphins, they fall into the nets — and dolphins also catch fish driven to them by the net
4. Both parties benefit — significantly higher catch for fishermen, and easier feeding for dolphins

Cultural significance:
In Myanmar and Cambodia, Irrawaddy dolphins are considered reincarnated ancestors — sacred animals. Harming them is taboo. In Chilika, specific dolphin pods are believed to be “attached” to specific fishing villages — a form of traditional ecological knowledge.

For UPSC: This relationship is evidence that human-wildlife coexistence is possible when local communities are invested in species’ survival. Traditional fishermen who depend on dolphins for better catches become their most effective protectors — a principle Project Dolphin’s “Dolphin Rescue Volunteers” programme tries to formalise. ★

The Indus River Dolphin’s situation in India is a textbook example of how infrastructure can ecologically devastate a wildlife population. ★

Historical range: The Indus River Dolphin historically ranged across ~3,500 km of the Indus River system — from the estuary (sea) up into the foothills of the Karakoram mountains. This included extensive sections in what is now India (Punjab, historically Sindh).

The partition of the Indus system: The Indus Waters Treaty (1960) between India and Pakistan divided river usage. India got the eastern rivers (Beas, Ravi, Sutlej) and Pakistan got the western rivers (Indus, Jhelum, Chenab). A tiny Indus dolphin population ended up in the Beas River on India’s side.

The Harike Barrage problem ★: The Harike Barrage was constructed at the confluence of the Beas and Sutlej rivers (near Harike, Punjab). This barrage effectively sealed off the small Beas dolphin population from the rest of the Indus system in Pakistan. The dolphins above the barrage cannot pass downstream, and no dolphins can come from Pakistan upstream. This isolated group — now just 3 individuals — is effectively genetically stranded.

Why didn’t more survive? The Beas River in India is heavily used for irrigation, heavily polluted by agricultural runoff, and has multiple small barrages. The remaining habitat is minimal and degraded. With only 3 individuals, the population is effectively below minimum viable population size — any further mortality could mean local extinction in India. ★

The 2024 national survey found these 3 dolphins in the Harike Conservation Reserve area — confirming their continued (barely) presence.

The Gangetic dolphin’s population history follows a pattern common to many endangered species — catastrophic decline followed by partial recovery when conservation measures took hold. ★

Historical decline:
At the start of the 20th century, Gangetic dolphins were abundant throughout the Ganga-Brahmaputra system — found even in major city ghats. By the 1970s, overhunting (for oil used in fishing and medicine), construction of barrages fragmenting rivers, and industrial pollution had severely reduced numbers. By the end of the 20th century, only ~4,000-5,000 dolphins were estimated. By the early 2000s, some surveys found as few as 1,800 individuals — an alarm bell that triggered conservation action.

What improved the situation:
1. Legal protection — Schedule I of WPA 1972 makes killing a dolphin equivalent to killing a tiger in terms of legal penalty
2. Vikramshila Sanctuary (1991) — provided a core protected zone
3. Ganga Action Plan (1986) — reduced some industrial pollution loads
4. Ban on dolphin hunting — traditional dolphin oil was used by fishermen but hunting was stopped through enforcement
5. Community engagement — local communities near Bhagalpur began protecting dolphins as a community asset

The 2024 count of 6,327: This is NOT purely a “recovery” figure — the methodology changed (first proper systematic survey using direct counts across 28 rivers and 8,507 km). The population has genuinely increased in areas with good protection but the new methodology also captured previously uncounted populations in tributaries. The Chambal River surprise — with very high dolphin density — was entirely new information. ★