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Hawaiian Monk Seal
Hawaiian Monk Seal
Common Name: Hawaiian Monk Seal
Scientific Name: Monachus schauinslandi
Hawaiian name: `ilio-holo-i-ka-uaua
Description
The Hawaiian monk seal was
listed as endangered throughout its range on November 23,
1976. Counts have been made at the atolls, islands and reefs
where they haul out in the northwest Hawaiian Islands since
the late 1950s. NMFS estimates that there are approximately
1400 animals. In 1982, the highest count for all atolls was
about 50 percent of the highest counts made in 1957-58. The
Hawaiian monk seal is most abundant on Kure
Atoll, Pearl and Hermes Reef, Lisianski Island, Laysan Island,
French Frigate Shoals, Necker Island and Nihoa Island. This
species is vulnerable to human disturbance on pupping and
haulout beaches, entanglement in marine debris,
incidental take in commercial fisheries, possible die-offs
from disease and naturally occurring biotoxins, male mobbing
of female seals, and shark predation.
An adult monk seal is usually
dark grey or brown with a light grey or yellow belly. Adults
can weigh anywhere from 396 to 595 pounds; adult females are
generally larger than males. Pups usually weigh 24 to 33 pounds
at birth and weigh up to 132 to 198 pounds within five to
six weeks.
The monk seal's common
name is derived from its folds of skin that look like a monk's
hood, and because it spends most of its time alone or in very
small groups.
Habitat & Behavior
Most Hawaiian Monk Seals
live in the Northwestern Hawaiian Islands - Kure Atoll, Midway
Atoll, Pearl and Hermes Reef, Lisianski Island, Laysan Island,
French Frigate Shoals, Gardner Pinnacles, Necker Island, and
Nihoa Island. These atolls and islands are very remote and
are either uninhabited or have little impact by humans, thus
providing an ideal habitat for these easily disturbed creatures.
The coral reefs found around
these atolls and islands provide the monk seal with
its food supply: spiny lobsters, octopuses, eels,
and various reef fishes. Their enemies include humans,
sharks, diseases, attacks from their own species,
and marine debris such as lost fishing nets
and plastic products.
Mothers stay with their pups from birth to about five or six weeks, never leaving them unprotected to go feed. During this time, she will lose as much as 300 pounds in weight. When she finally departs, the pup is on its own to learn to catch food.
They spend most of their time in the ocean
but like to rest on sandy beaches, and sometimes use beach
vegetation as shelter from wind and rain. Monk seals
are expert swimmers and divers; one seal was recorded diving
into depths in the range of 66 and 96 fathoms (396 to 576
feet). The average monk seal dives 51.2 times per day. The
life span of the Hawaiian Monk Seal is from
25-30 years.
Potential Threats
Food Limitation – A
critical threat that is regulating the population growth
in the Northwestern Hawaiian Islands (NWHI) is food limitation.
At French Frigate Shoals, the juvenile survival has declined
most dramatically. Because most of the monk seal population
occurs in the NWHI, this threat is of highest concern.
Entanglement – Hawaiian monk seals
have one of the highest documented entanglement rates of
any pinniped species, and marine debris and derelict fishing
gear are chronic forms of pollution affecting the Northwestern
Hawaiian Islands.
Shark Predation - There has been a significant
increase in shark predation on monk seal pups born at French
Frigate Shoals. Based on field observations, shark predation
may also be compromising recovery at Midway and Kure.
Infectious Diseases - Recent Main Hawaiian
Island monk seal deaths have heightened
concern about monk seal exposure to pathogens that they
have not previously encountered, such as leptospirosis,
toxoplasmosis, and West Nile virus, a pathogen that has
not yet been identified in Hawaii but is present in 47 other
states. The lack of antibodies in monk seals to
various viruses makes them extremely vulnerable to potential
infection. While the frequency of disease outbreaks may
be rare, their potential devastating effects, should they
spread throughout the population, makes infectious disease
a serious threat.
Habitat Loss - The loss of terrestrial
habitat is a significant issue of concern in the Northwestern
Hawaiian Islands (NWHI), especially habitat loss due to
environmental factors such as storms and sea level rise
that could further exacerbate this problem in the future.
While some habitat loss (e.g., the subsidence of Whaleskate
Island at French Frigate Shoals) has already been observed,
sea level rise over the longer term may threaten
Hawaiian monk seals in French Frigate Shoalsa large
portion of the resting and pupping habitat in the NWHI.
With the increased number of pups born in the Main Hawaiian
Islands, there is also a concern about adequate breeding
habitats without the potential for human disturbance at
popular beaches that have a high level of human activity.
Contaminants - Hawaiian monk seals
are exposed to organochlorines with concentrations of polychlorinated
biphenyls (PCBs) found in biological samples. Different
contaminants originating from human occupation of the Northwestern
Hawaiian Islands have been identified in monk seal habitat.
However, the effects of these compounds on monk
seal health, reproduction and survival are unknown.
Levels observed in monk seals are not elevated when compared
with other North Pacific pinnipeds.
Life History
Hawaiian Monk Seals were
first recorded in 1825 at the Hawaiian archipelago's northernmost
island, Kure Atoll. Scientist estimate about 1,300 to 1,400
monk seals live in the Hawaiian islands chain today. The species
has declined at approximately 11% per year since 1989 and
is the most endangered U.S.
Factors which threathen the persistence and
recovery of monk seal populations include
disturbance by human activities, interactions with fisheries,
mobbing of females by males, and shark predation. Although
not directly responsible for monk seal mortality, human activities
on beaches, even at low levels, can cause monk seals to abandon
haul-out areas. Such disturbance is particularly disruptive
to mother-pup pairs.
In the 1800s, shipwrecked crews ate them
in order to survive. By the early 1900s, humans were developing
commercial and military facilities in monk seal habitat.
Bottomfish, longline, and lobster fisheries
have all directly affected monk seals. Indirectly,
fisheries may affect seals through competition for prey or
entanglement in fisheries debris, such as lost or discarded
net and line. Mobbing attacks on adult and immature females
may be limiting the recovery of the Laysan and Lisianski populations.
Attacks by adult males result in known (minimum) deaths of
up to 10 or 11 seals annually at Laysan alone, which represents
approximately four percent of this island's populations. Monk
seals have been found dead with apparent shark-inflicted
wounds, and sharks have been observed feeding on dead seals.
Preservation Efforts
The Hawaiian Monk Seal
recovery efforts are overseen by the National Marine Fisheries
Service, in cooperation with other government and private
organizations and universities. The U.S. Fish and Wildlife
Service manages many remote islands as National Wildlife Refuges
to protect their habitat.
Research includes monitoring monk seal
reproduction, survival techniques, and behavior. In the
main Hawaiian islands, volunteer groups routinely remove marine
debris from the ocean and the beaches; in remote areas, the
U.S. Coast Guard and U.S. Navy lend a helping hand.
The Hawaiian Monk Seal was
listed as an endangered species in 1976 under the Federal
Endangered Species Act. Critical habitat was designated in
1988 from beaches to a depth of 20 fathoms (120 feet) around
the northwestern Hawaiian islands.
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