More on Whales

The first southbound Gray Whales have been spotted along the California coast, destined for Mexico where they spend the winter months breeding in shallow protected lagoons along Baja. Robustly 23,000 strong, almost all pass by my college town of Monterey twice a year on an epic 12,000 mile journey. Like the amber shades of autumn, the appearance of Gray Whales off the west coast of North America signals a change in the seasons, as reliable a natural rhythm as the Earth’s rotation around the sun. Here in the southern latitudes of the North Pacific a different species of whale, the humpback, marks the arrival of winter. Hawaiian locals and the illusive observant tourist alike are more than familiar with the acrobatic areal displays and haunting melodic songs of Humpback Whales in their waters. From December through March one is certain, if enough effort is given, to see the stunning foamy explosions of humpbacks flinging 40 tons of blubber from the surface, or to spot the tall bushy geyser of a whale’s exhalation on the horizon. Based on rather simple mark-recapture models, it is estimated roughly 20,000 humpback whales occur in the North Pacific Ocean, of which 8,500 to 10,000 breed throughout the main Hawaiian archipelago. There are of course other breeding populations throughout the tropical Pacific, all of which migrate between different feeding areas. For example the humpbacks I made a living off of watching during the summer in California travel to mainland Mexico and Central America, whales off of Siberia travel to southern Japan and the Philippines, and curiously enough based on recent DNA and photographic evidence there is a possible unknown breeding ground somewhere in the middle of the Pacific for whales that feed primarily around the Aleutians in Alaska. This got me thinking…French Frigate Shoals is about as middle of the Pacific as one can get…so I started digging.

Volunteer crews have spotted humpbacks from Tern Island in the past, but these observations were always anecdotal and typically of conspicuous whales breaching near the island. Thus far no dedicated effort has been given to visually sighting and documenting whales that possibly winter in French Frigate Shoals. In the spring of 2007, the 68 meter NOAA vessel RV Oscar Elton Sette departed Honolulu bound for the atolls and islands of the northwestern Hawaiian archipelago.  Carrying a crew of observers equipped with ‘big eye’ binoculars, they made a series of transects throughout the chain looking for signs of whale activity, however given the delayed timing of their departure, little activity was observed. In fact no whales what so ever were seen around French Frigate Shoals, with only a few scatted sightings around reefs further up the chain. Following this study in 2008, a team of researchers from the University of Hawaii deployed passive acoustic data loggers at seven locations along the chain, of which two devices were deployed at French Frigate Shoals. For reasons yet unknown, male humpbacks produce distinct songs unique to their source population that can travel many miles through the water column. The acoustic data were more encouraging than the transects that previous year, showing the rate of humpback song in French Frigate Shoals statistically matched that of a known breeding area near Oahu. Interestingly data yet to be published may reveal that humpbacks singing in French Frigate Shoals do in fact produce a slightly different song than whales in the main Hawaiian Islands, further adding evidence to the theory that the NW Hawaiian Islands are the missing breeding grounds of whales from the Aleutians. Again, this is just a theory.

Combing the ocean for signs of whales is almost an involuntary reflex for me now, and given the opportunity to contribute a bit of knowledge to this under sampled region, I’ve initiated of a dedicated whale watch. Elevation and good weather are crucial for observing whales. The warehouse roof offers a 360 degree view out to 12 kilometers, enough to search a decent portion of the atoll granted the weather cooperates.  Over the next three months I plan to scan the waters around Tern Island for at least one hour each day, in an effort to shed some light onto the number of whales, if any, which occur in this small segment of the world, along with the types of behaviors they may exhibit. Looking at the acoustic data and the opportunistic sightings from previous volunteers, whales begin to arrive around Tern in early December, peak in February, and drop off again in late March. I’ve already had my first confirmed humpback sighting on November 28^th, a lone individual that surfaced three times and disappeared. Based on what I’ve seen in Australia, this was likely an early singing male, which often appear cryptic at the surface and tend to stay down for over 20 minutes while singing – difficult to relocate once they dive. I’m hoping to get some significant counts in the coming weeks, possibly enough data for a poster to present at the Marine Mammal Conference in New Zealand in November of next year; giving me a particle excuse to travel down under again. Always have to think of the end game right?