(The Maui News)
Local false killer whales particularly vulnerable
October 9, 2010 - By HARRY EAGAR, Staff Writer
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Dan McSweeney was about 100 feet down in the water off Kona when a false killer whale offered to share his lunch: half of a mangled ahi that had weighed perhaps 175 to 200 pounds before encountering one member of the diminishing population of this little-known and distinctive Hawaii cetacean.
False killer whales - which look nothing like killer whales, the orcas - go about in pods of about 20, and they have a distinctive habit: When one captures a fish, it passes the catch around the group. Some just pass the fish on, others take a small bite first, until eventually the prey animal is returned to the hunter who killed it.
McSweeney was startled to be included in the exchange. The whale, which was about six feet away, shoved "a chewed-up chunk of ahi in my chest"; then swam below and behind McSweeney, blowing bubbles that rose around his swim fins.
McSweeney, who has been researching whales for 40 years, knew proper etiquette. Pass it on.
He said he "doesn't have a clue" about why he was included in the food exchange, but false killer whales "are really smart, bright creatures."
In more than a decade of paying special attention to them, he has found that "they don't seem aggressive toward people, but to give up that ahi, I found that very peculiar."
Only recently have researchers discovered that the local population of false killer whales, called the insular population, is genetically distinct from the roving, or pelagic, false killer whales. Their ranges overlap, but they do not interact.
In October 2009, the Natural Resources Defense Council petitioned the National Marine Fisheries Service to place the local population on the endangered list, a process that also would require designation of critical habitat.
The service has not announced its decision, but it recently released the assessment of its Biological Review Team, which found that Hawaiian insular false killer whales are at high risk of extinction within three generations (75 years), either from small, steady impacts or a single catastrophic event.
False killer whales (Pseudorca crassidens) are even less numerous than the more famous endangered local marine mammal, the Hawaiian monk seal, which has been losing up to 10 percent of its numbers each year and is down to little more than a thousand animals.
The local population of false killer whales may be down to around 150 or fewer, based on photographs, observations and satellite tracking. That is a reduction of perhaps two-thirds over a couple of decades, according to work by Robin Baird of Cascadia Research Cooperative, Joe Mobley of the University of Hawaii-West Oahu and others.
McSweeney, who came to Kona four decades ago to manage a dive tour company but soon got more interested in studying whales, said he used to see false killer whales commonly in the 1970s and '80s.
For years he was most interested in humpbacks (through his Wild Whale Research Foundation), but over the past decade he has become focused on false killer whales. It was not recognized originally that the local population does not interbreed significantly with the migrant, pelagic populations, which sometimes show up by the hundreds off the leeward coast of the Big Island.
The local population moves among all the main islands and has been seen up to 60 miles offshore. The whales, named false killer whales based on the resemblance of their skulls, range from shallow to very deep water and are highly social.
For that reason, the assessment team concluded that if the population falls below about 20, it will be unable to recover.
Baird, who was on the assessment team and also on a Take Reduction Team formed after Earthjustice sued the government, said that since the local population lives in the Hawaiian Islands Humpback Whale National Marine Sanctuary, "as the sanctuary considers adding new 'resources' to its mandate, the Hawaiian false killer whale should be at the top of the list."
Like humans, false killer whales are at the top of the food chain, and they like what people like: tuna, swordfish, monchong, mahimahi and ono. Competing with humans for sashimi probably has contributed to their decline.
However, McSweeney said they also carry high loads of toxins.
Because they eat predatory fish - already near the top of the food chain themselves - false killer whales will never be very numerous, although the insular population may have been the densest aggregation of these whales ever recorded.
Although much remains unknown about false killer whales, more is known about the Hawaiian population than any other. They live around the world in tropical and subtropical waters, occasionally venturing as far north as Canada.
The assessment group found that locally they face threats from the trolling, handline, shortline and kaka line fisheries; an increase in anthropogenic noise events; toxins; and susceptibility to the adverse biological effects of small population size.
"Fisheries interactions were postulated to be a major threat because extensive unobserved troll, handline and other hook-and-line fisheries target large pelagic fish and continue to operate at near-record levels in the Hawaiian insular false killer whale core area," the study found.
More information about false killer whales is at www.cascadiaresearch.org/hawaii/falsekillerwhale.htm.
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