For the first time, researchers are tracking by satellite a
group of “tropical oceanic” killer whales, a type rarely seen and
almost a complete mystery to scientists.
Observers with Cascadia Research
locate a group of four tropical oceanic killer whales, including
this male, near Hawaii. They were able to attach satellite tags to
three of them.
Photo by Aliza Milette
Researchers from Olympia-based Cascadia Research were in Hawaii,
on the final day of a 15-day research cruise to study marine
mammals, when they encountered four killer whales offshore from
Kona. They were the type of orca known to roam the open ocean, but
rarely seen by human observers.
In fact, in 14 years of research work in Hawaii, Cascadia’s
Robin Baird said he has encountered these tropical killer whales
twice before. Others have seen them on occasion, but sightings are
few and far between.
This time, on Nov. 1, Baird’s crew was able to obtain samples of
skin for genetic work, which will help determine how closely these
whales are related to other orcas throughout the world. The crew
also attached satellite transmitters to three of the four
Satellite tracks show the orcas
moving north and west over the past two weeks. (Click to enlarge
Map by Cascadia Research
Two of the transmitters are still transmitting nearly two weeks
later, and Baird hopes at least one will continue working for
several more weeks. In warmer waters, the barbed “tags” tend to
fall off sooner than in Northwest waters, Robin told me. As you can
see from the map, the whales first moved west, then north, then
west again. As of the latest plot this morning, they were west and
slightly south of Kauai.
By coincidence, two underwater photographers captured video and
still photos of these killer whales around the time the Cascadia
crew was in the area off Kona. Deron Verbeck and Julie Steelman
told KHON-TV that the experience was the pinnacle of their career.
(See video below.)
Although Nov. 1 was the last official day of the Cascadia
cruise, researcher Russ Andrews and several others went back out on
Saturday to find the four killer whales. They spotted three other
orcas with them. During the outing, they observed predation on a
thresher shark, something that photographer Verbeck also
Among the tropical oceanic killer
whales near Hawaii, this adult female swims with a young whale.
Notice the dark coloration of the saddle patch near the dorsal
Photo by Robin W. Baird
These tropical oceanic killer whales are smaller than the
familiar resident and transient killer whales of the Northwest,
Robin Baird explained. Instead of a white “saddle patch” near the
dorsal fin, these animals have a gray, almost black patch that is
difficult to see.
These are not the “offshore” killer whales that roam miles of
the West Coast, but generally stay on or near the continental
shelf, Robin told me. Still, it will be interesting to see if the
tropical oceanic orcas are closer genetically to the offshores,
which are known to eat sharks.
We do know the Southern Resident orcas, which frequent Puget
Sound, specialize in eating salmon, particularly chinook. But Robin
says whales feeding in the open ocean probably don’t encounter
enough of any one prey type to be so specialized. Considered
generalists, they have been known to eat squid, sharks, dolphins
and occasionally larger whales.
Some of the killer whales seen off
Hawaii had remoras, also called sucker fish, attached to them.
Experts say this is not unusual for tropical marine
Photo by Annie M. Gorgone
Robin says little is known about how they group together,
because the number of photo identifications is small. Generally,
the groups are five or less. The groups are likely to be families,
including a female and all her offspring. This is the same type of
matriarchal society found in other orca groups, although in some
orca societies — such Southern Residents — one matriline often
joins with others.
Robin says just about everything learned about their travels is
new, “from short-term movement rates, habitat use, and — if the
tags stay on for a while — how often they may visit island-habitats
(and) whether they cross international boundaries.”
In addition to Robin Baird and Russ Andrews, the research crew
on the trip included Daniel Webster, Annie Douglas and Annie
Gorgone, all from Cascadia; Amy Van Cise from Scripps Institution
of Oceanography and several volunteers.
Even before the killer whale encounter, the cruise was
considered successful, Robin said. Twelve species of marine mammals
were encountered, and satellite tags were deployed on six species,
now being tracked. More than 40,000 photographs were taken, some of
which are shown on
Cascadia’s Facebook page or the project
page on Cascadia’s website.
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