Article body copy
The adult dolphin carried the limp, dead calf on her back. Occasionally, the dolphin, presumed to be the mother, would dive into the water, taking the carcass with her. A half-dozen Chinese white dolphins followed closely, while a larger group trailed at a distance. When the procession met a boat, the trailing dolphins formed up, pushing themselves between the vessel and the central group.
“They were almost defensive,” says Matt Pine, a marine biologist at the University of Victoria in British Columbia, who watched the scene play out in Sanniang Bay, in southern China, in December 2014. Pine and his colleagues turned off the boat’s engine and lowered a hydrophone into the water, capturing audio of what they believe to be the sounds of dolphins grieving.
Chinese white dolphins, like other cetacean species, use songs and whistles to communicate while resting, socializing, and feeding. But after analyzing the whistles from the central group, Pine and his colleagues found that they were significantly longer and much more complex than calls the researchers were more familiar with. The recorded sounds included a greater number of inflection points, where the pitch of the whistles changed abruptly. This heightened complexity signifies that the dolphins were communicating a greater amount of emotional information, the researchers conclude in a recent paper.
Given the current state of scientific knowledge, it’s difficult to say precisely what the dolphins were expressing explains Zhaolong Cheng, the underwater acoustician from the Chinese Academy of Fishery Sciences who led the research team. But there are obvious, measurable differences between the whistles dolphins use in various situations, he says, suggesting they are communicating different emotions or information. Cheng speculates that in this case, the dolphins may have been expressing grief. After all, he adds, the whistles share acoustic similarities with those made by Chinese white dolphins that have been injured.
The journey of the dolphin and her dead calf is remarkably similar to that of the female killer whale J35, also known as Tahlequah, which captured the world’s attention last month when she carried her dead calf around the Salish Sea, off British Columbia, for 17 days.
Like the Chinese white dolphin mother, J35 was also accompanied by family members. Yet in J35’s case, other whales would sometimes help her carry her calf.
“There’s no way she could have not fed for 17 days and swam [around] the way she did,” says Lauren McWhinnie, a marine biologist at the University of Victoria who observed J pod, J35’s extended family, during parts of the ordeal. The family must have helped carry the calf so she could feed, McWhinnie speculates, “understanding that she wanted to keep this calf with her.”
J35 was not recorded during her ordeal, so scientists won’t be able to analyze her calls. Nevertheless, there was a notable incident when a group of females in the pod formed a circle around J35. “There was this heavy vocalization going on,” McWhinnie says, adding that although the calls are commonly made by these whales, the pod was much more vocal than normal.
Pine and McWhinnie are both cautious about anthropomorphizing marine mammals. The most they can definitively say is that the animals they observed were distressed. Whether what they were experiencing is anything akin to human grief, McWhinnie says, we may never know.