HAWAIIAN MONK SEALS
Our website pages pertaining to Hawaiian Monk Seal facts are updated annually with the most current data provided by the scientists from The Hawaiian Monk Seal Research Program, Pacific Islands Science Center (NOAA Fisheries), in Honolulu, Hawaii.
Hawaiian Monk Seals, (Monachus schauinslandi), are among the most endangered creatures on earth. They are one of only two mammals endemic to Hawai`i, the second being a species of bat. Often referred to as "living fossils", they have remained relatively unchanged for over 15 million years.
The Hawaiian archipelago, stretching from the big island
of Hawai`i northwestward past Midway Island, is the primary terrestrial habitat
of the Hawaiian Monk Seal (HMS). Approximately 85-90% of them live around the
tiny, uninhabited islands and atolls in the upper reaches of the chain. For
approximately 40-45 seals, the waters and beaches of Kaua`i are home.Some of
these seals regularly swim between islands and others are only seen on Kaua`i.
The adult HMS appears dark grey to brown on its top, or dorsal side, and a lighter grey to a yellowish brown underneath, the ventral side. Healthy adult HMS weigh from 400 to 600+ pounds, and range from 6 to 8 feet in length. Adult females are slightly larger than adult males.
Newborn pups have jet-black fur, which they lose as they approach the weaning period. Thereafter, they assume the dark grey coloring like that of mature seals.
The HMS is the most endangered marine mammal located entirely within U.S. waters. Monk seals rank second overall (after the Northern Right Whale, which ranges beyond US waters). The HMS is the most endangered pinniped in US waters, and second in the world. Among seals and sea lions, only the Mediterranean Monk Seal (monachus monachus) is more endangered. Small numbers of them survive near isolated caves and beaches in the otherwise heavily populated Mediterranean area. Their population is shrinking, with under 500 alive today. The Caribbean Monk Seal (monachus tropicalis), last sighted in 1952, is considered extinct. The total population of remaining Hawaiian Monk Seals is approximately 1,100 - 1,200.
During the 19th and early 20th centuries, sealers, shipwrecked
crews, feather hunters and guano diggers killed or so disturbed Hawaiian Monk
Seals that their numbers greatly diminished. From 1912 until the beginning of
World War II, HMS were spared from human activity over most of their range and
the population may have recovered somewhat. However, military activity during
and after World War II disturbed the seals once again. By the mid-1970s, beach
counts indicated that there were less than half the number of Hawaiian Monk
Seals than were counted in 1957 and 1958.
In 1976, the federal government listed the HMS as endangered under the Endangered Species Act. It was designated "depleted" under the Marine Mammal Protection Act the same year. A 50 percent decline in beach counts from the 1950s through the 1970s prompted these listings. Total population is estimated at about three times the beach counts, since not all seals are on the beach at any given time. In 1988, scientists designated critical habitat around breeding islands, ranging from beaches to a depth of 20 fathoms, or 37 metres, or approximately 120 ft.
It should be noted that harassing or disturbing an HMS
is a federal crime. Penalties upon conviction include fines of $25,000 or more
and up to 5 years imprisonment.
LOCATION AND DISTRIBUTION
The vast majority of HMS live on and around the Northwestern Hawaiian Islands, a chain of isolated atolls and tiny islands extending some 1,200 miles beyond Kaua`i. At least six locations with breeding populations can be found along this chain. Small populations of HMS inhabit the main Hawaiian Islandsmainly Kaua`i, Ni`ihau, O`ahu, and Moloka`i. Seals are increasingly sighted on the other islands. These habitats include sandy beaches and lava benches, their preferred haul-out sites. In the Northwestern Hawaiian Islands, scientists estimate that 90% of the seals are still residing at their birth islands by the time they become reproductively mature, and the other 10% can be found at a different location.
Mating of the HMS occurs in the water and has rarely been observed by humans. The gestation period is thought to be about 11 months. Most pups are born between February and July, although births can occur at any time of the year. While birth rates vary, on average, over half of all adult females pup each year. The female HMS reaches sexual maturity and can begin pupping as early as 4-5 years old, though most begin later. Preferred birthing sites are gently sloping beaches with adjoining shallow water. The obvious advantages are protection from sharks and ease of movement.
HAWAIIAN MONK SEAL PUPS
At birth, the HMS pup is approximately 1 metre, or 3 feet long and weighs between 25 and 30 pounds. In the ensuing six weeks, it will grow close to 200 pounds. A pup usually begins swimming with its mother from day one. In larger breeding populations, pups may be exchanged between nursing mothers, where more than one mom/pup pair are in close proximity.
After the six-week nursing period, the mother weans the pup abruptly, abandoning it to resume her own feeding.. The weanling pup will generally remain at its birth beach for a month or two. It will slowly begin to range farther out to sea and eventually learn to feed on its own.
Eels, lobsters, octopi, and small reef and bottom fish are prey for the Hawaiian Monk Seal. Data from limited studies indicates that most of their feeding occurs at depths between 75 and 90 metres or less, which is approximately 245-300 ft. These seals have occasionally been known to dive as deep as 500 metres, or 1640 ft. The maximum recorded depth, greater than 500 metres, occurred near French Frigate Shoals. Dive lengths average 6-7 minutes, although dives of over 20 minutes have been recorded. Dive durations reaching over 15 minutes likely include "sleeping dives" , where the animal shoves itself into a coral "puka", or hole, for brief rest.
Newborn seals, or pups, feed only on mothers milk from birth to about six weeks of age. Nursing mothers do not usually eat during the six-week period. However, they have been observed eating a little in the last few days before weaning. While they do not go on active hunting trips, some appear to feed on prey that happens to swim nearby.
The full lifespan of the Hawaiian Monk Seal is believed to be in the range of 25-30 years, yet not all of them reach this age. Scientists have little data, as most tagged seals of known age are less than 20 years old.
CAUSES OF MORTALITY
In the Northwestern Hawaiian Islands, where about 85-90% of Hawaiian Monk Seals live, a variety of factors can shorten their lifespan. Scarcity of prey may cause emaciation and subsequent death to juveniles. While the tiger shark is the main predator of the HMS, pups and weakened or emaciated seals are susceptible to lesser breeds of shark as well. Entanglement in marine debris can also result in seal fatalities. From ongoing health studies of the HMS, diseases do not appear to currently limit population recovery, but scientists do know that disease can quickly spread through seal poplulations.
In breeding populations, if males greatly outnumber available females, a behavior called "mobbing" may occur. A large group of adult males, particularly at Laysan and Lisianski Islands, can batter, or mob, a female or immature seal to death.
Around Kaua`i and the other main, inhabited islands of Hawai`i, lack of prey, emaciation, and mobbing do not appear to be factors in seal longevity. Entanglement in marine debris and the potential for collision with boat propellers are known threats. The tiger shark remains the one significant predator of the HMS, but healthy, well-fed seals are much more capable of eluding or withstanding attack. Documentation of disease transmission between HMS and dogs and people is incomplete, but the potential is huge. Other species of seal have experienced significant die-offs from diseases like distemper, probably caught from other animals.
Perhaps the biggest day-to-day risk factor involving the endangered Hawaiian Monk Seal on Kaua`i is human disturbance. Kaua`i has a unique situation where a critically endangered species comes into daily contact with people. Consequently, almost all the activities of the Kaua`i Monk Seal Watch Program are geared toward protecting the seals hauled out on our beaches, and educating visitors and residents alike.
HMS molt annually, differing in time by age group and sex. Adult males molt in late fall or early winter. Females will molt around two months after weaning a pup. Other adult females usually molt in springtime, while immature seals' molting periods change as they age. During a one-and-a-half to two-week span, the HMS loses its entire layer of skin and overlying fur. The old skin and brown mottled fur strips away, leaving a sleek, dark grey coat underneath.
Molting seals often seem distressed. They may have mucous around the nose and runny eyes. They remain on the beach for longer periods than usual and often appear uncomfortable, writhing in the sand to help remove skin. Also, the stench from the molting skin can be quite unpleasant when one is in close proximity to the animal. While these conditions might lead someone to assume that an HMS is sick or injured, they are part of a normal annual cycle.
Two possible explanations for the name "monk seal" exist, and both are considered plausible origins. First, the excessive folds of skin around the head and neck of the seal somewhat resemble a monks hood. Secondly, their solitary nature brings to mind a monk-like existence. Unlike similar pinniped species which colonize, HMS are usually seen alone, or occasionally in the company of one or two other seals.
To find out more information on HMS and its protection, see Links