A rare, endangered baby dolphin has been spotted swimming with another species in Cambodia, baffling scientists.
Irrawaddy dolphin (Orcaella brevirostris) the calf was probably with its mother in a group of Indo-Pacific humpback whales (Sousa chinensis). Irrawaddy dolphins are dark gray and have flattened faces, while Indo-Pacific humpback dolphins are pink and have long noses, so the calf and mother stick out like saw thumbs.
Scientists at Marine Conservation Cambodia (MCC) announced the sighting on May 31, posting on Facebook that the interaction was “extremely unusual” because the two species usually only meet while feeding in the same area.
Becky Chamberslead scientist for the Cambodian Marine Mammal Conservation Project at MCC, told Live Science that her team was very excited to spot the calf, but wasn’t sure why the two species were together.
“It’s a bit of a mystery,” Chambers said. “Both of these dolphin populations are very endangered and the fact that they are interacting, I wouldn’t say it’s either good or bad at this point.”
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Irrawaddy dolphins, known for spitting water from their mouths helping people catch fish, are at risk of extinction, partly due to entanglement in fishing gear. Scientists don’t know how many Irrawaddy dolphins remain in the wild, but their population is severely fragmented, a study shows. IUCN Red List.
Chambers and her colleagues were surveying dolphins off the coast of southern Cambodia on March 12 when they first encountered a young Irrawaddy dolphin calf. “We see minors quite often, but it was a newborn, which is an event in itself,” she said.
Irrawaddy dolphins have been known to interbreed with Indo-Pacific humpback dolphins, but this is extremely rare, and according to the Facebook post, this calf had all the physical characteristics of an Irrawaddy dolphin calf. This means he was probably born to two Irrawaddy dolphin parents.
Both species can engage in alloparenting - caring for young that are not direct offspring - which may, on rare occasions, involve other species. However, it is unclear whether the Indo-Pacific humpback whales were trying to help care for the calf or harm it.
Chambers noted that Indo-Pacific dolphins may have tried to separate the mother from her calf in an act of aggression, perhaps motivated by competition. “I’m on the fence about whether it was an aggressive interaction or not,” she said.
However, it appears that the calf has lived out its time with the Indo-Pacific humpback dolphins. On April 23, one of Chambers’ colleagues apparently spotted the calf again. This time, the researcher followed a lone Indo-Pacific humped dolphin, which, to their surprise, swam to a group of Irrawaddy dolphins. It is also unclear why the Indo-Pacific humpback whale joined the group of Irrawaddy dolphins, but that group of Irrawaddy dolphins had a young calf and Chambers believes it was the same one spotted with the group of Indo-Pacific humpback dolphins.
“They didn’t have a good camera, so you couldn’t get a photo ID on this occasion, but it’s probably the same person, which is good because it means the calf is still alive,” Chambers said. .