High-tech transmitters giving up secret lives of Hawaiian seals
By Diana Leone
Advertiser Staff Writer
Up to 15 monk seals in Hawai'i will be doing their part over the coming year to help scientists understand them better.
The critically endangered animals will wear small transmitters that reveal their movements, including how deep they dive, when they haul out on land and how far they roam.
Accumulating normal habits of the seals also will be used to gauge the effect Navy training exercises, including use of sonar, may have on the animals.
The Navy is footing the bill for the $4,500-each transmitters, NOAA scientists' travel and veterinary costs associated with the project. The project is slated to last several years.
Currently five seals are wearing the transmitters — one on O'ahu and four on Moloka'i. Additional transmitters will be placed on 10 more seals on Kaua'i and O'ahu in coming months, said Charles Littnan, lead scientist for NOAA Fisheries' Hawaiian Monk Seal Research Program.
The transmitters are slightly larger than a deck of cards with a short antenna and are glued to fur on a seal's back, where it will least interfere with its daily life. Pregnant, nursing, sick or wounded seals, or seals near to their annual molt of their fur will not be tagged, Littnan said. Only seals of 200 pounds or more will be tagged.
The transmitters "are a lot like a smartphone," Littnan said. They show a seal's location with global positioning coordinates and also track water temperature, salinity and depth of dives. They "phone home" when the seals are on the surface of the water or on land and the devices can transmit via a cell phone tower, Littnan said.
So far, an O'ahu seal dubbed "Kermit" by seal protection volunteers has been the star of the project. Several tagged seals lost their transmitters, prompting a change in the glue used to attach them, and the Moloka'i seals have only recently been tagged.
Already, Littnan knows that Kermit travels regularly back and forth between Diamond Head and Nānākuli. Some of his favorite fishing grounds seem to be offshore from 'Ewa Beach. The seal often spends 12 to 24 hours at a time swimming and diving in the ocean, then hauling out at a variety of beaches for a rest.
"Monk seals dive pretty much from the time they hit the water through their entire trip," Littnan said. "Depth varies, but duration of each dive is usually around six minutes, and surface times usually about one or two minutes. They feed almost entirely along the bottom, which is why the dives are so flat."
Most of Kermit's dives are in the 100- to 150-foot range, but his record dive since wearing the transmitter was to more than 700 feet. Seals in the Northwestern Hawaiian Islands have been recorded diving as deep as 1,500 feet on occasion.
The seals' dives are all about food. Seals are "generalists" in what they eat, Littnan said. But they "focus almost entirely on things on the bottom — tako, eels, flatfish like flounder, some reef fish — wrasses, triggerfish — and a variety of crustaceans, including lobster and crabs."
One of the mysteries of the breed is why the seals living in the main Hawaiian Islands are doing so much better than their cousins in the remote islands, which are protected as part of the Papahānaumokuākea Marine National Monument.
"There's a stark contrast ... the animals down here have better survival and are in much better condition," Littnan said. "They're fatter, which is good for seals."
"It seems really counterintuitive, because the Northwestern Islands people describe as a relatively pristine environment," Littnan said. In the main islands, there is enormous pressure from recreational and commercial fishing. There's sewage going into the ocean. All these human disturbances — and monk seals are just thriving."
A working theory behind the success of seals in the main islands and the distress of those in the Northwestern Hawaiian Islands is that the rich population of large predators, including ulua and sharks, in the remote islands are direct competitors with the seals for their favorite foods.
Underwater video in the Northwestern Hawaiian Islands has shown ulua and sharks following behind seals as they turn over rocks on the sea floor to find fish — and eating the fish before the seals can get them.
There are other issues, too, including predation on seals by Galapagos sharks and entanglement in marine debris.
There are an estimated 150 monk seals in the main Hawaiian Islands and about 950 in the northwestern part of the chain. The seals live in the wild only in Hawai'i and as a group have had steep overall population declines in recent years.
If trends continue, in 15 years the monk seal population of the main and Northwestern Hawaiian Islands could both be about 400 to 500 animals, Littnan said.
Information gathered from the tracking project should help answer the question, "What is that going to mean?" Littnan said. "And are there enough resources to support them?"
NOAA researchers get first crack at the data as they come in and use them to try and help the endangered seals survive. The Navy will work with NOAA after a quantity of baseline data has been accumulated to see if it can detect any changes in seal behavior when there Navy training activities, including use of sonar, Littnan said.
A statement from the Navy said it is funding the $198,165 project as part of its compliance with the federal Marine Mammal Protection Act for its U.S. Pacific Fleet's Hawai'i Range Complex.
This is the first year of what's expected to be a multi-year project, Littnan said.
"The monitoring plan commits the Navy to visual surveys, passive acoustic monitoring and tagging of marine mammals, including monk seals, to determine habitat use relative to Navy training events as well as any behavioral response," U.S. Pacific Fleet spokesman Mark Matsunaga said.
Littnan said: "This is going to be important stuff for the Navy and for the monk seals."