Field Season for Hawaiian Monk Seal Population Research Draws to Close

Hawaiian monk seal.

PIFSC biologists have completed most 2009 field operations directed at monitoring of the highly endangered Hawaiian monk seal. From May through August, field staff worked at monk seal breeding locations throughout the Northwestern Hawaiian Islands where they collected data for population assessment, including counts of adult, subadult and newborn seals. They recorded at least 115 monk seal pups born this year: 31 at French Frigate Shoals, 30 at Laysan Island, 17 at Lisianski Island, 13 at Pearl and Hermes Atoll, 9 at Midway Atoll, 5 at Kure Atoll, and 9 on Nihoa Island. In addition, field staff in the main Hawaiian Islands documented the birth of 16 pups: 6 on Molokai, 4 on Kauai, 2 on Oahu, 1 on Maui, and at least 3 on Niihau.

Besides monitoring population abundance, seal biologists relocated weaned pups to lower their risk of predation. In August, they collected six weaned seals from French Frigate Shoals, an area of low pup survival, and released them at Nihoa Island, where their survival is expected to be higher. This is the second year of a pilot study to try to increase juvenile seal survival. The experiment will help determine the feasibility of using such relocations to increase juvenile survival, particularly survival of females.

A new aspect of monk seal research this year was a de-worming trial, in which several juvenile seals at Laysan Island were given the first of several doses of medication to eliminate parasitic worms from their bodies. De-worming medication will be given to the selected seals four times during the next year. To accomplish the work, a field camp will be maintained at Laysan Island over the winter. The body condition and survivorship of treated seals and non-treated (control) juveniles will be monitored and compared to determine if reducing worm burden boosts overall health of the seals.