Dolphins are the stuff of fantasy art and feel-good movies. But what do you know about dolphins of the Philippine seas?
By Regina Layug Rosero
With additional text by Charlene Bobis
The Irrawaddy dolphin is one such dolphin. It can be found in Palawan, primarily the Malampaya Sound in Taytay. In 2013, a new population was reported off the coast of Quezon, also in Palawan. Previously, Irrawaddy dolphins were also spotted near the island of Panay.
This endangered dolphin is not unique to the Philippines though. There are isolated populations in other Southeast Asian countries too, like Indonesia, India, Papua New Guinea, Cambodia, Thailand and Lao. The name Irrawaddy actually comes from the Ayeyarwady River in Myanmar. Its scientific name is Orcaella brevirostris. The people of Palawan call it “Lampasut.”
Whatever you call it, it’s certainly an interesting creature! Here are the basics of what you need to know about it.
1. Where do they live?
Irrawaddy dolphins like both marine and freshwater environments. They’re usually found in “shallow, near-shore tropical and subtropical marine waters,” like “estuaries and semi-enclosed water bodies such as bays and sounds, usually close to mangrove forests.” The ones who live in freshwater environments are
found in river systems.
2. Wait, dolphins can live in rivers?
Definitely! Aside from Irrawaddy dolphins, there are other known species of river dolphins. Try looking up any of these: Chinese river dolphin, Ganges river dolphin, Indus river dolphin and Franciscana (la plata) dolphin.
It’s behavior rather than biology that makes it a river dolphin; actionasia.com clarifies that it “…is not a true river dolphin, but an oceanic dolphin that lives in brackish water near coasts, river mouths, and in estuaries.”
3. What are its physical features?
According to worldwildlife.org, “These dolphins have a bulging forehead, short beak, and 12-19 teeth on each side of both jaws.” WWF.panda.org describes them thus, “The pectoral fin is broadly triangular. There is a small dorsal fin, on the posterior end of the back. When diving, this dolphin breathes at intervals of 70-150 seconds; the head appears first and then disappears, and then the back emerges, but the tail is rarely seen. Head and body length is 180-275 cm.
Irrawaddy dolphins are slaty blue to slaty gray throughout, with the underparts slightly paler.” Interestingly, because they have no “beak” the way other dolphins do, Irrawaddy dolphins’ snouts (with upturned mouths and short noses) make it look like they are smiling. Due to their blunt head shape, they closely resemble the Beluga whale.
4. What do they eat?
Irrawaddy dolphins eat fish, crustaceans (that means animals like shrimp, krill and barnacles), cephalopods (such as squid and cuttlefish), and fish eggs. Those who have seen them feeding were amused to note that these dolphins spit water from their mouths. The Convention on the Conservation of Migratory Species of Wild Animals says this is done to herd fish the way the dolphin wants them to go. 5. Do they socialize?
They have been observed to travel in groups of six adults at most, but in Malampaya in the Philippines, a group of 20 was spotted a few years ago by a member of a world animal organization. Solo-living dolphins are extremely rare, if at all.
6. How do they make baby dolphins?
Like all mammals, Irrawaddy dolphins bear live young. Marinebio.org reports, “Little is known about the reproductive habits of Irrawaddy dolphins. It is thought that they reach sexual maturity when they are around 4-6 years old. Their mating season is believed to occur between April-June in the Semayang Lake/Mahakam River area of Kalimantan, Indonesia, based on the birth of calves born in captivity in Jakarta between July-December.
Their gestation period is estimated at about 14 months. Newborns measured following birth in captivity were 96 cm long and weighed 12.3 kg. During their first 7 months, calves increased in length by 57 cm (59%) and in weight by 32.7 kg (266%). One calf was nursed for about 2 years, although it began consuming fish at 6 months.” What concerns marine biologists and conservationists is that the populations of these dolphins that have been observed have low reproduction rates, birthing young only once every three years, according to the Convention on the Conservation of Migratory Species of Wild Animals.
7. How fast can they swim?
Not very fast, actually. Most fact sheets describe them as slow swimmers, and are considered to be less active than other dolphins. When they swim, only their uppermost dorsal surface is visible as they execute rolling dives. Don’t expect the Irrawaddy dolphin to do the high leaps other dolphins are famous for; they leap out of the water only occasionally, and only for low heights.
They have also never been observed to bow-ride the way other dolphins do. Like most of its kind, the Irrawaddy dolphin breathes at long intervals (usually 70-150 seconds) when it dives. When it breaks the surface, you’ll see its head first and part of its back, but rarely, if ever, will you see its tail.
8. What are their idiosyncrasies?
In addition to herding fish by spitting water, they “…have even been reported to stun large fish with a blow from the lower jaw, only to play with them before casting them aside,” says cms.int. Irrawaddy dolphins have been known to interact with humans. According to cms.int, fishers at their namesake river (known these days as the “Ayeyawady River”) “…practice castnet fishing with the help of Irrawaddy dolphins. Dolphins and fishermen communicate by audio and visual signals during fishing.”
This is mutually beneficial for both dolphins and humans, as zero catches were significantly lessened when the dolphins worked with the humans, and one assumes they got to eat the fish that spilled over from the nets.
This appeared in Animal Scene’s March 2016 issue.