If not attacked and killed or whatever, they drown.
https://www.yahoo.com/lifestyle/dying-orcas-final-moments-desperate-143536714.html
Dying orca's final moments after 'desperate' effort
to stay afloat captured in 1st of its kind footage
Whale-watchers spotted an orca (Orcinus orca) — a
roughly 35-year-old male known to researchers as
Hunchy after his hunched back — behaving strangely
in waters north of the island of Loppa in Norway
on Nov. 6. Two younger orcas huddled close to
Hunchy, seemingly holding him at the surface so he
could breathe, Pierre Robert de Latour, the author
of "Frère des Orques" (Glénat, 2019) who has been
diving with orcas in Norway for over 20 years and
was on the whale-watching expedition, told Live
Science.
The attempt to keep Hunchy afloat seemed "desperate,"
Robert de Latour said, adding that "it was obvious
that he was in trouble."
Robert de Latour got into the water and snorkeled up
to the orcas to take a closer look. He noticed the
old male looked skinny, and the shape of his belly
suggested he hadn't eaten for a long time.
The footage shows Hunchy floating motionless just
below the ocean surface after the two younger orcas
left the scene. The young pair swam back and forth
between Hunchy and a group of orcas further away,
Robert de Latour said, repeatedly trying to
"activate" the old male.
The young orcas realized that if they left Hunchy,
he would sink to his death, he added. (Orcas can
stay submerged for up to 15 minutes, but they
usually come to the surface to breathe every
minute when resting, and every three to five
minutes when traveling.)
But after 50 minutes, they seemingly gave up. "They
were helping him until the very last moment,"
Robert de Latour said.
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