A fish-versus-whale battle seems like no contest. But two whales learned otherwise when common soles became lodged either in or just below their blowholes, slowly suffocating them to death.
Though observed before, the rare phenomenon has never been recorded in long-finned pilot whales, a new study says. The body of one animal washed up on the Dutch coast in late 2014, the other in early 2015.
Making the deaths doubly strange, pilot whales normally dine on squid, not flatfish such as soles, and they prefer deeper waters than the relatively shallow seas in which they perished. (Also see "How a DVD Case Killed a Whale.")
Experts think that loyalty to a companion may have done the whales in. Both animals were swimming in unfamiliar territory and eating unfamiliar food, perhaps out of a reluctance to abandon a family member in distress, says study co-author Lonneke IJsseldijk, a biologist in the Faculty of Veterinary Medicine at the University of Utrecht.
Even crueler, the animals, which can hold their breath a long time, would have had suffered, experts say. Death “wouldn’t have been as quick … as for a human,” says Sue Barco, research coordinator for the Virginia Aquarium & Marine Science Center, who was not affiliated with the study.
“It would’ve been a crappy way to die.”
Both corpses were so rotten that IJsseldijk, who was called to examine them, initially thought she couldn’t learn much. But her first examination, of a young male, revealed an entire fish stuck in the whale’s nasal passages, which lead from the blowhole to the lungs.
The second whale, a mature female, was more striking still. IJsseldijk could see a fish’s tail protruding from the female’s blowhole. The fish was so tightly jammed that in trying to pull it out, the scientist tore it apart. (See "Dead Whale Contains a Bounty of Life.")
It’s unlikely that the fish swam into the whales’ bodies after the whales died, since common sole are worm-eaters, not scavengers, says IJsseldijk, whose study was published November 18 in the journal PLOS ONE.
The acrobatic fish can roll up in almost any direction and fling themselves off the ocean floor, making it possible that they flipped into the whales’ nasal passages as they tried to escape. It’s also possible that a forceful sneeze or cough from the whales forced the fish, which also died, down the wrong way.
So why were these whales hanging around this unfamiliar place?
In a possible clue, a pilot whale pod was seen off the Belgian coast shortly before the discovery of the suffocated whale bodies. A week later, animals from what seemed to be the same pod seemed about to strand themselves on an English beach before volunteers drove them into deeper waters. (Also see "337 Whales Beached in Largest Stranding Ever.")
Shortly after that, the body of an emaciated young pilot whale was found at the same spot.
The researchers think the pod members may have stayed with their distressed compatriot, probably a relative, until she died. When a pilot whale is sick or hurt, its podmates “will all follow that animal,” says IJsseldijk.
“They will not leave it dying somewhere on its own, even if they risk getting stranded.”
Both Barco and Kerri Danil, a marine mammal research biologist with the U.S. National Oceanic and Atmospheric Administration, think IJsseldijk and colleagues presented a plausible scenario for the pilot whales’ deaths.
Though the cause is bizarre, it’s important to document why whales die and prey that may harm them, Danil says via email.
The ability to examine whales after death “is always important,” Barco says. “We don’t get a chance to look at them very often in their natural environment.”
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