Human Effects On Whales And Dolphins
A number of recent news articles have been discussing the impact of humans on whales and dolphins. Oil tankers are high on the list of environmentalist when they look at human directed harm to whales and dolphins. The greatest fear is an oil spill such as the Exxon Valdez oil spill. Orcas, in particular, suffer at population level from the chronic toxicological effects of large oil spills. These long lived cetaceans reproduce infrequently, producing a maximum of six calves during each female's lifetime. Over the last twenty years, there has been no record of calves born into the transient killer whale group (AT1) from Prince William Sound, Alaska. After the Exxon Valdez oil spill, 15 of the 22 whales in this pod disappeared and although only five of their carcasses were recovered, the remaining ten individuals are in all probability also dead. These individual whales are considered to have died from preying on oiled harbor seals and from the inhalation of oil vapors.
Oil tankers as well as other ocean going vessels kill a large number of whales and dolphins each year. They either collide with the marine life inflicting possibly fatal blunt force drama and one of the animals can be hacked to death by passing to closely to the propellers.In the case of the northern right whale, the critically small population of 300 animals is found predominantly within major shipping lanes. Over 34% of the moralities within this small population have been attributed to collisions with vessels. The ever increase marine traffic means an increasing risk of injuries to these and other species.
Noise is another factor that can lead to harm to whales and dolphins. Sound waves travel further underwater and seem louder. The sounds of the ships' propellers can carry for miles and disorientation the marine life. As dolphins and many whales use sound as part of its social interaction and as a mean of locating each other and meals, the man made sound waves can have a disastrous effect. Sonar has been a concern since it was first introduced in WWII. In recent years another item has entered the list of concerns. This is the off-shore wind farms. The greatest risk of damage is during the construction phase. Pile drives can be heard for long distances and at a short range cause physical damage to the creatures' hearing.
Many people feel greater study and care need to be made to safeguard these mammals.