With these senses they are aware of where they are through feeling different water temperatures or tasting water types. This is useful if sight or echolocation are restricted. In the open seas and in coastal waters, dolphins are in danger. In many parts of the world, stranded dolphins are often found to have swallowed plastic bags or have nylon straps wrapped around their tail flukes. Fortunately this is uncommon off the South African coast, but as our population and the production of plastics and other wastes increases, our dolphins may still have to face this problem.
Toxic pollutants come from two main sources, agriculture and industry.
Agricultural pollutants include DDT, dieldrin and lindane, all of which are still used in pest control and public health. The main industrial pollutants are PCBs, a group of highly toxic substances. Recent research suggests that dolphins, particularly the males, are unable to rid themselves of toxic pollutants and because of this and the continued accumulation of pollutants in the marine environment, some dolphin populations may become extinct within the next 100 years. Pollution also includes non-toxic effluent such as sewage and waste water which is pumped into rivers and the sea by industry and cities. Bad agricultural practises causing soil erosion result in soil and silt accumulation in the inshore region.