Mission Log: July 7, 2006
Researching the Hawaiian Monk Seal on Kure
The majority of the Hawaiian monk seals are found in the Northwestern Hawaiian Islands from Nihoa Island to Kure Atoll with a small number on the main Hawaiian Islands. Traditionally Monk seals have been killed for food by early sailors. The species was declared depleted under the Marine Mammal Protection Act in 1976 following a 50% decline in beach counts. Monk seals were also classified as “endangered” under the Endangered Species act in 1976. Undersized female pups from the French Frigate Shoals were rehabilitated and released on Kure from the 1980’s until 1995 in an attempt to re-establish populations.
Approximately 90% of the monk seals remain at the island where they were born for life. During our recent visit to Green Island, I interviewed monk seal researchers Tracy Wurth and Antonette Gutierrez from the National Marine Fisheries Service. Tracy and Antonette have been in the field on Green Island since May 16, 2006 collecting data on the monk seal population.
|A young monk seal pup recently weaned. (Photo: James Watt)
Most pups are born between February and July with the peak in April and May. The newly born pup is totally black and weighs approximately 20 to 30 lbs. By the time they are weaned (30 to 40 days) they will increase their weight to over 100 lbs. Monk seals in the Northwestern Hawaiian Islands tend to wean their pups sooner at approximately 30 days, while seals on the Hawaiian Islands tend to nurse longer; as many as 60 days. Northwestern Hawaiian Island pups tend to be smaller in size as a result. Females give birth on beaches with shallow water to protect their pups from sharks. A female will not give birth until they reach five to ten years of age. By the time the researchers arrive on Green Island most female seals will have already pupped.
Tracy and Antonette conduct seal patrols on Green Island on a daily basis. They walk the beach collecting information on each seal observed. Approximately every fourth day they conduct an atoll count, which is a standardized seal patrol that is time sensitive and basically captures a “snapshot” of the population at a given time. For their atoll counts the seal team start their survey on Green Island at 1:00 pm and when finished take their boat to Sand islet and conduct a survey there. Atoll counts take the researchers approximately three hours.
|Monk seal biologist, Tracy Wurth, discusses the importance of seal scat with the educators. (Photo: Claire Johnson/NOAA)
Field researchers from the National Marine Fisheries Service on all the Northwestern Hawaiian Islands keep careful track of each seal in the colony; identifying individuals with applied tags and bleach marks as well as natural markings or scars. Every seal is photographed by taking photos of all sides and flippers and are documented in a digital photo library. New pups are tagged as soon as they are weaned at 30 to 40 days. Plastic “temple” tags are applied to each rear flipper and injected with a micro-chip pit tag. Flipper tags are color specific to each island; Kure uses grey tags, while Pearl and Hermes uses light blue tags. The letter assigned will tell researchers what year the pup was born. One pup with a bleach mark “Z26” swam close enough to our boat for us to read his marks. Later the researchers knew exactly what seal we had seen and told us it was a “weaner;” a pup born is this year that had already weaned.
During the field season information is collected on injuries, wounds, illnesses, abnormalities, as well as deaths/disappearances, births, and any unusual events. If a dead seal is found a necropsy is performed and samples from organs and tissues are collected. Researchers also collect specimens of scat and spew (vomitus) in an effort to analyze the monk seal’s diet. Tissue plugs are taken from tagged pups for DNA analysis to determine maternity. Priorities for the Kure researchers include all of the above, while male aggression and shark predation mitigation is not a significant problem here at Kure Atoll. However, researchers are concerned about the future seal population due to low juvenile survival. As the current breeding females get older or die there will not be younger seals to take their place in the breeding population.
|Tracy Wurth and Antonette Gutierrez from NOAA Fisheries conduct atoll counts to get a "snapshot" of the monk seal population at Kure Atoll. (Photo: Patricia Greene)
Researchers also collect marine debris such as nets on shore or in shallow water and move it to a secure location to be picked up at a later date by the National Marine Fisheries Coral Reef Ecosystem Division. The collection of marine debris is extremely important because monk seals can become entangled in the nets.
At Kure Atoll, the adult seal population in 2005 was 86 individuals with 23 pups born. The population at Kure has been slowly decreasing over the last several years. One major factor is the low juvenile survival rate due to lack of nutrients and resulting emaciation. However, this year their numbers show an increase in juvenile survival with a re-sight rate of over 60 percent. In the past the re-sight rate has been closer to only 30 percent.
While on Kure Atoll, the researchers enter their data in the field database system. When the researchers return from their assignment they will file their final report. This information will be summarized in published papers and used by various institutions such as the Hawaiian Monk Seal Recovery Team.
The future of the protected monk seal is unclear. Today, researchers estimate the total monk seal population in existence is approximately 1,300 to 1,600 seals. Researchers are concerned if the population continues to decline the total number could fall below 1,000 within the next five years. Scientists and researchers work together to find solutions to aid the recovery of the Hawaiian monk seal.