Thursday, March 19, 2009

New information further tangles Hanalei whale stranding

The cause of a 2004 stranding event involving melon-headed whales at Hanalei Bay gets more interesting as time passes.

And so does the role of the moon.

(Image: Melon-headed whales circling in tight formation in Hanalei Bay July 3, 2004. Credit: NOAA.)

A new scientific paper published in February concludes that military mid-frequency played a major role, and that there's no consistent evidence that the phase of the moon did. The Hanalei stranding and a simultaneous stranding in Rota, the Mariana Islands, happened at the full moon.

But just when you start leaning hard in one direction, the foundation of your assumptions gets shaky. To muddy the water, of two Philippines strandings of melon-headed whales this year—after the new paper was published—one of those, too, happened at the full moon.

More precisely, the day after the night of the full moon, same as with Hanalei and with Rota.

Science ever requires reconsidering your conclusions based on new data.

This gets complicated. Stick with us.

In the continuing controversy over the Navy's use of sonar, and the larger role of noise in the marine environment, the prime bit of Hawai'i evidence is the apparent stranding incident in Hanalei Bay on a day in 2004 on which the Navy was using mid-frequency sonar.

A new paper compares that incident with other stranding and near stranding incidents involving the same species, the melon-headed whale. None of the other cases is known to involve sonar activity.

The paper, “Behavior of melon-headed whales, Pepnoncephala electra, near oceanic islands,” in the journal “Marine Mammal Science,” was written by Robert L. Brownell Jr of NOAA 's Southwest Fisheries Science Center, Katherine Ralls of the Smithsonian Institution's National Zoological Park, Simone Baumann-Pickering of Scripps Institution of Oceanography, and Michael Poole of the Marine Mammal Research Program in Moorea, French Polynesia.

They compared the Hanalei incident with a stranding that took place at precisely the same time in Sasanhaya Bay, Rota, near Guam. They also considered melon-headed whale behavior at different times at Nuku Hiva in the Marquesas Islands of French Polynesia, and at Palmyra, the Line Islands atoll where the Hawaiian voyaging canoe Hokule'a is scheduled to arrive today.

Researchers in a previous paper in 2006 concluded that sonar was a more than possible cause of the Hanalei stranding:While causation of this stranding event may never be unequivocally determined, we consider the active sonar transmissions of July 2-3, 2004, a plausible, if not likely, contributing factor in what may have been a confluence of events.”

Others, notably Hawai'i researchers Joe Mobley and Paul Nachtigall, along with Navy researchers David Fromm and Stephen Martin, in the Journal of the Acoustical Society of America, have suggested that lunar cycles or other factors could be associated with the unusual simultaneous Hanalei and Rota strandings.

In the Hanalei case, nearly 200 melon-headed whales entered the north-facing bay about 7 a.m. July 3. The animals remained in the bay, alternately swimming in small groups and milling in one group. Brownell's team called it “prestranding behavior.”

Navy sonar activity was being conducted offshore in conjunction with RIMPAC exercises. A Japanese ship nearly 30 miles away used sonar to the northwest of Kaua'i about 15 minutes before the whales entered the bay. The National Marine Fisheries Service, informed of the whale event during the day, asked the Navy to halt sonar use, which it did about 5 p.m.

The next morning, residents using canoes escorted the whales out of the bay. A newborn whale calf that washed ashore dead. “It must have been separated from its mother at some point during the event and died from dehydration,” the Brownell paper says.

Melon-headed whale strandings are far from unknown, and they have been reported occurring in the Pacific for as long as people have been watching them. In an 1841 case in Hilo, native Hawaiians in canoes are reported to have forced a stranding by driving nearshore melon-headed whales to the beach.

In the Rota case, which was going on at the same time as the Hanalei event, Brownell and his team said the whale behavior did not look like a stranding event; rather, the whales congregated without apparent panic in the bay, and later left.

But Mobley and his team argued that you couldn't ignore two near-shore appearances of large numbers of the same kind of whale, at the same time, nearly 4,000 miles apart.

“Beyond the extraordinary coincidence of these two events, at a minimum, the Rota event indicates that aggregations of this type may have natural causes totally independent of sonar activity,” wrote Mobley and his team.

In the July 2005 Nuku Hiva case, melon-headed whales congregated in a bay, and while they were there, three killer whales stranded—but the melon-headed whales did not.

“...both MHWs and killer whales behaved as if they were fleeing from some strong aversive stimulus. Perhaps this was the case but we have been unable to identify a likely candidate for such a stimulus, so the cause of the Nuku Hiva MHW event remains unknown,” Brownell and co-authors write.

The Palmyra stranding occurred in 1959, and melon-headed whales are frequently observed near shore at Palmyra.

Brownell's group said they compared the stranding dates with moon phase data, and found no correllation. But Brownell specifically excludes Rota from his lunar phase study, saying it wasn't a proper stranding.

The Navy argues that none of the events was a proper stranding, since aside from the dead calf, which washed ashore at a different Kaua'i beach near Hanalei, none of the melon-headed whales actually swam up onto the beach.

“In reality, none of the events are actually "strandings" since in none of the events did melon-headed whales actually strand,” said Mark Matsunaga, environmental public affairs officer for the U.S. Pacific Fleet.

Browning calls the Hanalei incident a stranding and Rota not a stranding, largely based on reports of how the whales behaved—that they cruised apparently normally at Rota and appeared anxious at Hanalei.

But the whole argument about melon-headed whales and full moons took a new turn with a February melon-headed whale stranding in the Philippines also happened the day after the full moon, the same as the Hanalei and Rota events.

On Feb. 10, the day after the full moon, local fishermen helped guide several hundred melon-headed whales back to deep water in Bataan Province of the Philippines.

A second apparent stranding in the Philippines occurred at the half moon, a week before the next full moon, about March 4.

In the latest paper, Brownell says Hanalei's incident was different from all the others. If anything, compared to their 2006 conclusion, the researchers even more securely pin the blame on the Navy.

“Our review of (melon-headed whale) behavior strengthens the case that (mid-frequency sonar) use played a major role in the near MS in Hanalei Bay,” they write.

The Navy itself doesn't deny some role for sonar in the Hanalei incident, but argues for scientific caution.

“Much remains to be learned about cetaceans, including melon-headed whales,” Matsunaga said.

“Brownell's study is certainly not the final word on melon-headed whale aggregations. Even if one accepts that all scientific studies are subjective and selective by nature, we believe Brownell has overstepped."

He notes that the Mobley team in 2006 “indicated mass strandings are more common during the full moon and third quarter.

“That is not to say that lunar influences cause strandings, but they may result in animals being closer to shore in some environments and thus, serve as a contributing factor. Marine mammals strand for a variety of reasons, some of which are still unknown,” Matsunaga said.

One issue is whether birthing has anything to do with the full moon strandings. The baby whale found dead near Hanalei was just a week old. Two of four dead whales found near one of the February Philippine strandings were females, one of which was pregnant and one of which had just given birth.

Here is a line from the Convention on Migratory Species:

“Mass strandings of melon-headed whales have been reported from Moreton Island and Crowdy Heads, Australia, Malekoula Island, Vanuatu, the Seychelles, Aoshima, Japan, Piracanga Beach, Brazil, the Kwajalein Atoll, and Tambor, Costa Rica. It has been noted that in several mass strandings of this species, the ratio of females to males was about 2:1. This may reflect behavioural segregation.”

That raises the whole issue of human interference. If melon-headed whales have a history of entering bays and nearshore waters en masse, they also have a history of getting themselves out of those bays without help.

Except for handful of dead animals found on the beach the whales in most of these incidents did not physically strand themselves--did not run themselves up on the beach a la Whalerider.

What's the appropriate human response in this situation--they appear to be in distress, or at least behaving unusually, but do not appear to be in immediate danger?

©2009 Jan TenBruggencate

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