Dolphins

Context: A new study has found that noise generated by human activity makes it harder for dolphins to communicate and coordinate with each other.

Highlights of the study:

• Dolphins are social mammals that communicate through squeaks, whistles and clicks.
• They also use echolocation in order to locate food and other objects.
• As the levels of underwater noise increase, these mammals have to “shout” to each other.
• Echolocation occurs when an animal emits a sound wave that bounces off an object, returning an echo that provides information about the object’s distance and size.
• Therefore, anthropogenic noise coming from large commercial ships, military sonars or offshore drilling can severely impact their well-being.

About Dolphins:

River Dolphins:

• There are only six extant species of river dolphins left in the world today and they are all endangered or critically endangered.
• This is because pollution, dams, shipping and bycatch have taken their toll on this iconic species.
• There are currently 42 species of dolphins and seven species of porpoises.
• Dolphins are marine mammals.
• They must surface to breathe air and give birth to live young.
• A dolphin pregnancy last between nine and 16 months.
• The mother feeds her offspring on milk.
• The sons and daughters of resident orcas stay with their maternal family for life.
• Dolphins eat fish, squid and crustaceans.
• They do not chew they food but may break it into smaller pieces before swallowing.
• All dolphins have conical-shaped teeth.
• A Risso’s dolphin has 14 while a spinner dolphin can have 240.
• The orca (killer whale) is the largest dolphin.
• Hector’s dolphin and Franciscana are two of the smallest.
• The four river dolphin species inhabit the large waterways of Asia and South America.
• Dolphins have an array of vocalisations such as clicks, whistles and squeals which they use for their well-developed communication and echolocation skills.
• Lifespan varies from around 20 years in the smaller dolphin species to 80 years or more for larger dolphins such as orcas.
• Maui’s dolphin (a sub-species of the New Zealand dolphin) is the most endangered dolphin.

Consequences of noisy oceans:

• Marine animals are known to use sound to navigate, find food and protect themselves.
• As sound travels faster in water than air, it makes for an important mode of communication because it can convey a lot of information quickly and over long distances.
• Scientists believe that fish species rely on sounds during reproductive activities, including mate attraction, courtship and mate choice.
• Sounds made by drilling, commercial ships and military operations lead to disruption of marine life.

Source:  Indian Express

Previous Year Question

Q.1) Certain species of which one of the following organisms are well known as cultivators of fungi? (2022)

1. Ant
2. Cockroach
3. Crab
4. Spider