Over a dozen species of dolphin live in the waters in and around Sri Lanka, ranging from huge pilot whales to dancing spinner and spotted dolphins.
The genus, together with other cetaceans, is the focus of a great deal of ecotourism, with whale watching trips bringing considerable foreign currency to the island.
This article will educate you about the lifestyle, threats and species that inhibit the waters of Sri Lanka.
Species
Shy pygmy killer whales and pelagic melon-headed whales are rarely seen by humans, but they live all year round near Sri Lanka.
Risso’s dolphins are also a deep-water species that avoided humans, but they occasionally surf bow waves, as do rough-toothed dolphins.
Huge pods of Fraser’s and striped dolphins sometimes appear, and the acrobatics of shallow-water spinner dolphins are a frequent sight.
Athletic spotted dolphins often play around boats, as do two species of bottlenose dolphins.
White Indo-Pacific humpbacks appear at times, as do killer whale and false killer whales.
In addition to dolphins, the finless porpoise also inhabits the area.
Diet
Larger dolphins favor squid as the mainstay of their diets, while smaller animals prefer fish.
The spotted dolphins that swim with yellow fins do not feed off the tuna; rather, the two species share a common diet of smaller fish.
While some killer whales eat fish, others favor marine mammals.
The two types do not live together.
Some species such as the striped dolphin and finless porpoise will eat almost anything from shrimp and krill through cephalopods up to good-sized fish.
Social Structure
Many dolphin species live in pods.
For some types, only ten or twelve individuals may live together, but Fraser’s and striped dolphins in particular may swim in groups of several hundred.
Dolphin families tend to be matrilineal, consisting of a female and her close relatives.
In only a few species do male dolphins remain with their birth pods.
Female pilot whales and orcas go through menopause, the only animals other than humans to do so, and those who are past reproduction remain with their pods and assist in raising the calves of younger dolphins.
Breeding
Dolphins appear to enjoy breeding.
Their sexual encounters are not limited to efforts made during reproduction, and they may include activities with members of the same-sex or with other species.
Young are born tail first after a gestation period that lasts anywhere from 11 to 17 months, depending on the species.
In spite of collective efforts at calf care, infant mortality is extremely high in some species.
Up to half of all infant killer whales, for instance, die before they are six months old.
Some species are not as nurturing as others; male bottlenose dolphins for instance sometimes kill infants of their own kind.
Habitat
The many diverse species of dolphins mean that they live can be found in most waters.
Some prefer deeper parts of the sea, while others are shallow water animals.
Some, like orcas, prefer cold water, and so visit tropical areas like Sri Lanka only rarely, but many love the warm waters near the island.
Some dolphins are very shy about people, but others joyfully play with boats full of humans.
The wide variety of dolphin species is one advantage that these creatures have in their struggle for survival.
Threats
Dolphins are large animals.
Most are as big or bigger than an average human.
As such dolphins have very few natural enemies.
Some species are also known as apex predators, meaning they aren’t hunted by any other animals.
Others need worry only about large sharks.
Dolphins sometimes get parasites and diseases, but for the most part their biggest enemy is humans.
Sri Lankan poachers sometimes use illegal nets that threaten dolphins, and dolphins may even be hunted for human consumption.
Tour operators may get too close to wild populations and disturb them.
Other threats include habitat destruction as well as chemical and noise pollution, but many species of dolphin flourish in the environment around Sri Lanka in spite of all this.