Hawaiian Monk Seal
Encyclopedia
The Hawaiian monk seal, Monachus
schauinslandi, is an endangered
species
of earless seal
in the Phocidae family
that is endemic
to the Hawaiian Islands
.
They are solitary animals, like some monks. The Hawaiian monk seal is one of two remaining monk seal species; the other is the Mediterranean monk seal
. A third species, the Caribbean monk seal
, is extinct.
The Hawaiian monk seal is the only seal native to Hawaii
.
These monk seals are a conservation reliant endangered species
. The small population of about 1,100 individuals is threatened by human encroachment, very low levels of genetic variation
, entanglement in fishing net
s, marine debris
, disease, and past commercial hunting for skins. There are many methods of conservation biology
when it comes to endangered species
; translocation
, captive care, habitat clean up, and educating the public about the Hawaiian monk seal are some of the methods that can be employed.
comes from short hairs on its head, said to resemble a monk
.
(Phoca ‘’vitulina’’). The monk seal’s physique is ideal for hunting its prey: fish
, lobster
, octopus
and squid
in deep-water coral
beds. When it is not hunting and eating, it generally basks
on the sandy beaches and volcanic rock of the Northwest Hawaiian Islands.
The Hawaiian monk seal is part of the Phocidae family, being named so for its characteristic lack of external ears and inability to rotate its hind flipper
s under the body. The Hawaiian monk seal has a relatively small, flat head with large black eyes, eight pairs of teeth, and short snouts with the nostril on top of the snout and vibrissae
on each side. The nostrils are small vertical slits which close when the seal dives underwater. Additionally, their slender, torpedo-shaped body and hind flippers allow them to be very agile swimmers.
Adult males are 300 to 400 lb (136.1 to 181.4 ) in weight and 7 feet (2.1 m) in length while adult females tend to be slightly larger, at400 to 600 lb (181.4 to 272.2 ) pounds and 8 feet (2.4 m) feet in length. When monk seal pups are born, they average 30 to 40 lb (13.6 to 18.1 ) and 40 inches (1 m) in length. As they nurse for approximately six weeks, the grow considerably, eventually weighing between 150 to 200 lb (68 to 90.7 ) by the time they are weaned
, while the mother loses up to 300 lbs.
Monk seals, like elephant seals, shed their hair and the outer layer of their skin in an annual catastrophic molt. During the most active period of the molt, about 10 days for the Hawaiian monk seal, the seal remains on the beach. The hair, generally dark gray on the dorsal side and lighter silver ventrally, gradually changes color through the year with exposure to atmospheric conditions. Sunlight and seawater cause the dark gray to become brown and the light silver to become yellow-brown, while long periods of time spent in the water can also promote algae growth, giving many seals a green tinge. The juvenile coat of the monk seal, manifest in a molt by the time a pup is weaned is silver-gray; pups are born with black pelage. Many Hawaiian monk seals sport scars from shark
attacks or entanglements with fishing gear. Maximum life expectancy is 25 to 30 years.
In an effort to inform the public and conserve the seals, the National Oceanic Atmospheric Administration (NOAA) Fisheries Service has written a historical timeline of the Hawaiian monk seal to demonstrate that the Hawaiian islands has been home to the seals for millions of years and that the seals belong there. Evidence points to monk seals making their way to Hawaii between 4-11 million years ago (mya) through an open water passage between North and South America called the Central American Seaway
. The Central American Seaway was closed by the Isthmus of Panama approximately 3 million years ago so the Hawaiian monk seal has been separated from its congeners for at least to near extinction in the Northwestern Hawaiian Islands
, but soon after the population had started to slowly increase in numbers.
Authors of the book Marine Mammals: An evolutionary biology, Annalisa Berta and James Sumich, ask questions about how this Hawaiian monk species came to the Hawaiian Islands when its closest relatives are found on the other side of the world in the North Atlantic and Mediterranean Sea
. No one knows if the Hawaiian monk seal is the oldest or the youngest seal in the Monachus genus. The species may have evolved in the Pacific or Atlantic, but in either case, it came to Hawaii long before the first Polynesians
in approximately
plasticity
which allows them to be opportunistic predators that feed on a wide variety of available prey.
takes nine months to develop, with birth of the pups occurring in March and June. The pups usually weigh about 16 kg and are about 1 m long. Pups are born with a black coat which they shed at about six weeks and replace with a gray coat on the back and white on the belly. The pups are born on beaches and nursed by their mothers for about six weeks. After that time, the mother will desert the pup, leaving it on its own, and return to the sea to forage for the first time since the pup’s arrival.
s and Galapagos shark
s are both predators of the Hawaiian monk seals.
Scars are found on many of the monk seals as a result of their encounters with these predators. Also, female monk seals have scars from aggressive male monk seals. Furthermore, a recent study showed that the monk seals are dying from a pathogen
in cat feces (toxoplasmosis
) that is carried to the ocean in polluted runoff and sewage water, which is a new threat to this endangered species. Over the past ten years, the cat parasite has killed at least four monk seals in the main Hawaiian Islands. In addition to toxoplasmosis, other pathogens have infected monk seals with leptospirosis
being one of the biggest concerns. Additionally, Hawaiian monk seals also have frequent human encounters from commercial fishermen and tourists.
Seal populations have declined rapidly in recent years due to the rapid spread of human activity to even the most remote and isolated areas in the Hawaiian Islands. In the nineteenth century, Hawaiian monk seals were clubbed to death by whalers
and sealers
for meat, oil and skin. U.S. forces hunted them during World War II
while occupying Laysan Island and Midway
.
As the result of human disturbances, ciguatera
poisoning, high male to female ratios occurred during the breeding season, and entanglement in fishing net
s and debris have killed many animals. In the northwestern Hawaiian islands, starvation is a serious problem. Lobster
s, the seals' preferred food other than fish, have been overfished and competition from other apex predators such as sharks, jacks
, and barracuda
s, leaves little left over for developing pups. The creation of Papahānaumokuākea Marine National Monument enclosing these islands may lead to more abundant food supplies.
In areas where male seals outnumber females, several males may compete for a single female, known as mobbing, often accidentally killing the female. Females of any age including pups can become targets.
These threats have taken a toll on the species. It has been nearly eradicated from the main Hawaiian Islands. The population there is approximately 150. It is currently found on Laysan
, Midway
, Pearl and Hermes Atoll
, French Frigate Shoals
, and Lisianski
.
In the summer of 2009, two monk seals were shot and killed.
Slowly, however, the monk seals are returning to the main Hawaiian Islands. Lone seals have been sighted in surf breaks and on beaches in Kauai
, Niihau
, Maui
, O'ahu's Turtle Bay
, and even spotted on Waikiki beach on March 4, 2011, outside of the Moana Hotel
. They often leave the water haul out on busy tourist beaches, where they are vulnerable to disturbance. In early June 2010, 2 seals were seen hauled out on Oahu's popular Waikiki beach. NOAA has cultivated a network of volunteers who protect the seals while they bask or bear and nurse their young. In 2006, twelve pups were born in the main Hawaiian Islands, rising to thirteen in 2007, and eighteen in 2008. As of 2008 43 total pups have been counted in the main Hawaiian islands. Tiger sharks also prey on them which also damages the monk seal population.
NOAA is funding considerable research on seal population dynamics and health in conjunction with the Marine Mammal Center.
(M. monachus) is even rarer, and the Caribbean monk seal
(M. tropicalis), last sighted in the 1950s, was officially declared extinct in June 2008. The population of Hawaiian monk seals is in decline. In 2010, it was estimated that only 1100 individuals remain. It is listed as critically endangered. The Hawaiian monk seal was officially designated as an endangered species on November 23, 1976, and is now protected by the Endangered Species Act
and the Marine Mammal Protection Act
. Today, even though the islands are protected, many scientists believe that the effects of human activity along these fragile coastlines (and in the world at large) are still taking their toll
It is illegal to kill, capture or harass a Hawaiian monk seal.
To raise awareness for the species' plight, the Hawaiian monk seal was declared Hawaii
's official State Mammal on June 11, 2008 by Lieutenant Governor James Aiona
.
The multitude of factors that play a role in the limitation of population growth seen in the critically endangered Hawaiian monk seal can be seen as the primary natural facets and the anthropogenic impact of the past and present. Several natural factors affecting the recovery of the Hawaiian monk seal include the low genetic variability observed in populations, low juvenile survival rates, reduction of habitat/prey associated with environmental changes, increased male aggression, and subsequent skewed ratios amongst the sexes. Anthropogenic or human impacts to monk seals include hunting (during 1800s and 1900s), human disturbance, entanglement in marine debris, and fishery interactions.
species, the Hawaiian monk seal has the lowest level of genetic variability. A study found that this low genetic variability is due to a population bottleneck
caused by intense hunting in the 19th century. This lacking in genetic variability reduces the species ability to adapt to environmental pressures and limits natural selection
thus increasing their risk of extinction. One such environmental pressure that may be detrimental to the monk seal would be the presence of an infectious disease;in such small populations the effects of a disease could be disastrous. One possible infectious agent affecting the overall health of the species could be from ciguatera
poisoning. Another possibility arises from postmortem examinations of seal carcasses revealing gastric ulcerations caused by parasites, which would negatively affect the health of the seal.
Additionally, low juvenile survival rates continue to threaten the species. High juvenile mortality is due to starvation, shark predation, and marine debris entanglement. A reduction in habitat and subsequently a reduction in prey abundance associated with environmental changes results in a decrease in seal populations due to starvation. The critical habitat is being lost due to erosion in the Northwest Hawaiian Islands, which is shrinking the islands/beaches and proving to be very problematic for the monk seal. Another huge contributor to the low juvenile survival rates is the predation from sharks. Most mature monk seals are scarred from previous encounters with sharks and many such attacks have been observed. Additionally, marine debris entanglement can result in mortality because the seals get trapped in debris such as fishing nets and cannot escape.
Furthermore, mobbing, a practice among the seals that involves a large number of seals attacking one seal in mating attempts, is responsible for many deaths especially to females. Mobbing leaves the targeted individual with many wounds that lead to septicemia and the seals then die from infection. In a study performed by Gilmartin et al., it was found that a small population of monk seals was more likely to experience a mobbing problem as a result of the increased male-biased sex ratio and male aggression. It was also observed that unbalanced sex-ratios were more likely to occur in slow-growing populations, therefore until the population reaches a large or rapidly growing population state, biased sex-ratios and mobbing will continue.
Entanglement in marine debris is another huge impact from people that cause great damage to the seal populations, despite international law prohibiting the intentional discarding of debris from ships at sea. Monk seals have one of the highest documented rates of entanglement of any pinniped species; a huge problem that current studies indicate there is no sign of it abating in the future.
Marine fisheries can potentially interact with the monk seals via direct and indirect relationships. Directly the seal can become snared by fishing equipment, entangled in discarded debris, and even feed on fish refuse. While the possible indirect effects have yet to be documented, they include the effect overfishing may have on the prey abundance of the monk seal, negatively effecting the seal’s diet and habitat.
Identification and mitigation of these and other possible factors (e.g., disease) limiting population growth represent ongoing challenges and are the primary objectives of the Hawaiian monk seal conservation and recovery effort.
Public outreach and education remain the most powerful tools for promoting the conservation of the Hawaiian monk seal and its habitat. Human proximity and entanglement in marine debris kill many animals. For instance, large beach crowds and beach structures limit the seal’s habitat.
In 1909, President Theodore Roosevelt
created the Hawaiian Islands Reservation that included the Northwest Hawaiian islands. The Reservation later became the Hawaiian Islands National Wildlife Refuge (HINWR) and moved under the jurisdiction of the U.S. Fish and Wildlife Service (USFWS). This marine sanctuary greatly benefited the seals.
As anthropogenic impacts are reduced, natural factors affecting population growth must also be addressed.
Genetic data analysis is needed because identifying individuals genetically along with confirming maternity and paternity can provide information about male and female reproductive rates which are crucial to wildlife managers.
“Headstart” began in 1981, collected and tagged female pups after weaning, and placed them in a large, enclosed water and beach area with food and lacking disturbances. The female pups remain during the summer months, leaving at roughly age three to seven months.
Another project began in 1984 at French Frigate Shoals
. It collected severely underweight female pups, placed them in protective care and fed them. The pups were released as yearlings and relocated to the Kure Atoll
.
Some habitats are better suited to increase survival probability making relocation a popular and promising method. Although no direct links between infectious diseases and seal mortality rates have been found, unidentified infectious diseases could prove detrimental to relocation strategies.
Monachus
Monachus is a genus containing the monk seals, a group of three Pinniped species. They are the only earless seals which are found in tropical climates...
schauinslandi, is an endangered
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of earless seal
Earless seal
The true seals or earless seals are one of the three main groups of mammals within the seal superfamily, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae...
in the Phocidae family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
that is endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to the Hawaiian Islands
Hawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
.
They are solitary animals, like some monks. The Hawaiian monk seal is one of two remaining monk seal species; the other is the Mediterranean monk seal
Mediterranean Monk Seal
The Mediterranean monk seal is a pinniped belonging to the Phocidae family. At some 450-510 remaining individuals, it is believed to be the world's second-rarest pinniped , and one of the most endangered mammals in the world.It is present in parts of the Mediterranean Sea and the eastern Atlantic...
. A third species, the Caribbean monk seal
Caribbean Monk Seal
The Caribbean monk seal or West Indian monk seal is an extinct species of seal. It is the only seal ever known to be native to the Caribbean Sea and the Gulf of Mexico. The last verified recorded sighting occurred in 1952 at Serranilla Bank...
, is extinct.
The Hawaiian monk seal is the only seal native to Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
.
These monk seals are a conservation reliant endangered species
Conservation reliant species
Conservation reliant species are endangered or threatened animal or plant species that require continuing species specific wildlife management intervention such as predator control, habitat management and parasite control to survive even when self-sustaining population recovery goals are...
. The small population of about 1,100 individuals is threatened by human encroachment, very low levels of genetic variation
Genetic variation
Genetic variation, variation in alleles of genes, occurs both within and among populations. Genetic variation is important because it provides the “raw material” for natural selection. Genetic variation is brought about by mutation, a change in a chemical structure of a gene. Polyploidy is an...
, entanglement in fishing net
Fishing net
A fishing net or fishnet is a net that is used for fishing. Fishing nets are meshes usually formed by knotting a relatively thin thread. Modern nets are usually made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and...
s, marine debris
Marine debris
Marine debris, also known as marine litter, is human created waste that has deliberately or accidentally become afloat in a lake, sea, ocean or waterway. Oceanic debris tends to accumulate at the centre of gyres and on coastlines, frequently washing aground, when it is known as beach litter or...
, disease, and past commercial hunting for skins. There are many methods of conservation biology
Conservation biology
Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...
when it comes to endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
; translocation
Translocation (Wildlife conservation)
Translocation in wildlife conservation means capture, transport and release or introduction of species, habitats or other ecological material from one location to another...
, captive care, habitat clean up, and educating the public about the Hawaiian monk seal are some of the methods that can be employed.
Etymology
Known to native Hawaiians as Ilio-holo-i-ka-uaua, or "dog that runs in rough water", its scientific name is from Hugo Hermann Schauinsland, a German scientist who discovered a skull on Laysan Island in 1899. Its common nameCommon name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
comes from short hairs on its head, said to resemble a monk
Monk
A monk is a person who practices religious asceticism, living either alone or with any number of monks, while always maintaining some degree of physical separation from those not sharing the same purpose...
.
Description
Its grey coat, white belly, and slender physique distinguish them from their cousin, the Harbor sealHarbor Seal
The harbor seal , also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere...
(Phoca ‘’vitulina’’). The monk seal’s physique is ideal for hunting its prey: fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
, octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
and squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
in deep-water coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
beds. When it is not hunting and eating, it generally basks
Hauling-out
Hauling-out is the behaviour associated with pinnipeds , of temporarily leaving the water between periods of foraging activity for sites on land or ice...
on the sandy beaches and volcanic rock of the Northwest Hawaiian Islands.
The Hawaiian monk seal is part of the Phocidae family, being named so for its characteristic lack of external ears and inability to rotate its hind flipper
Flipper (anatomy)
A flipper is a typically flat limb evolved for movement through water. Various creatures have evolved flippers, for example penguins , cetaceans A flipper is a typically flat limb evolved for movement through water. Various creatures have evolved flippers, for example penguins (also called...
s under the body. The Hawaiian monk seal has a relatively small, flat head with large black eyes, eight pairs of teeth, and short snouts with the nostril on top of the snout and vibrissae
Vibrissae
Vibrissae , or whiskers, are specialized hairs usually employed for tactile sensation. The term may also refer to the thick hairs found inside human nostrils, but these have no sensorial function and only operate as an airborne particulate barrier...
on each side. The nostrils are small vertical slits which close when the seal dives underwater. Additionally, their slender, torpedo-shaped body and hind flippers allow them to be very agile swimmers.
Adult males are 300 to 400 lb (136.1 to 181.4 ) in weight and 7 feet (2.1 m) in length while adult females tend to be slightly larger, at400 to 600 lb (181.4 to 272.2 ) pounds and 8 feet (2.4 m) feet in length. When monk seal pups are born, they average 30 to 40 lb (13.6 to 18.1 ) and 40 inches (1 m) in length. As they nurse for approximately six weeks, the grow considerably, eventually weighing between 150 to 200 lb (68 to 90.7 ) by the time they are weaned
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...
, while the mother loses up to 300 lbs.
Monk seals, like elephant seals, shed their hair and the outer layer of their skin in an annual catastrophic molt. During the most active period of the molt, about 10 days for the Hawaiian monk seal, the seal remains on the beach. The hair, generally dark gray on the dorsal side and lighter silver ventrally, gradually changes color through the year with exposure to atmospheric conditions. Sunlight and seawater cause the dark gray to become brown and the light silver to become yellow-brown, while long periods of time spent in the water can also promote algae growth, giving many seals a green tinge. The juvenile coat of the monk seal, manifest in a molt by the time a pup is weaned is silver-gray; pups are born with black pelage. Many Hawaiian monk seals sport scars from shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
attacks or entanglements with fishing gear. Maximum life expectancy is 25 to 30 years.
History and evolution
The evolutionary history of the monk seal is controversial since there are different hypotheses for the phylogenetic to other phocids. Due to the lack of fossil records, there is little evidence supporting that the Hawaiian monk seal is related to other seals in the Phocidae family; thus, there remains a great deal of debate on the evolution of the Hawaiian monk seal. Based on the prehistoric and unspecialized skeletal and vascular anatomy of the seal, many scientists have stated that the Hawaiian monk seal is considered the most primitive of living seals. These scientists offer the hypothesis that the Hawaiian monk seal was the decedent of the Caribbean species, M. tropicalis; all three monk seals are said to have originated in the North Atlantic and these scientists believe the Hawaiian monk seal became separated from its congeners as early as 15 million years ago.In an effort to inform the public and conserve the seals, the National Oceanic Atmospheric Administration (NOAA) Fisheries Service has written a historical timeline of the Hawaiian monk seal to demonstrate that the Hawaiian islands has been home to the seals for millions of years and that the seals belong there. Evidence points to monk seals making their way to Hawaii between 4-11 million years ago (mya) through an open water passage between North and South America called the Central American Seaway
Central American Seaway
The Central American Seaway, also called the Panamanic Seaway or Inter-American Seaway was an ancient body of water that once separated North America from South America...
. The Central American Seaway was closed by the Isthmus of Panama approximately 3 million years ago so the Hawaiian monk seal has been separated from its congeners for at least to near extinction in the Northwestern Hawaiian Islands
Northwestern Hawaiian Islands
The Northwestern Hawaiian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niihau. They are administered by the U.S. state of Hawaii except Midway Atoll, which has temporary residential facilities and is...
, but soon after the population had started to slowly increase in numbers.
Authors of the book Marine Mammals: An evolutionary biology, Annalisa Berta and James Sumich, ask questions about how this Hawaiian monk species came to the Hawaiian Islands when its closest relatives are found on the other side of the world in the North Atlantic and Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. No one knows if the Hawaiian monk seal is the oldest or the youngest seal in the Monachus genus. The species may have evolved in the Pacific or Atlantic, but in either case, it came to Hawaii long before the first Polynesians
Polynesians
The Polynesian peoples is a grouping of various ethnic groups that speak Polynesian languages, a branch of the Oceanic languages within the Austronesian languages, and inhabit Polynesia. They number approximately 1,500,000 people...
in approximately
Habitat
The majority of the Hawaiian monk seal population can be found around the Northwest Hawaiian Islands but a small and growing population can also be found on the main Hawaiian Islands. These seals spend two-thirds of their time at sea, and one-third on the sandy beaches. Early studies (done at Midway Atoll) concluded that these seals frequently stayed inside the lagoons as opposed to the deep ocean, because of the larger abundance of fish found in the coral reefs of the lagoons. However, recent use of animal-born video imaging, temperature/depth recorders, and satellite telemetry has shown that monk seals actually spend much more time foraging in deeper water outside the reefs (sometimes to subphotic depths of 300 meters or more). Hawaiian monk seals breed and haul-out on sand, corals, and volcanic rock; sandy beaches are more commonly used for pupping. Due to the immense distance separating the Hawaiian Islands from other land masses capable of supporting the Hawaiian monk seal, its habitat is limited to Hawaii and its Northwestern Islands.Diet
Hawaiian monk seals mainly prey on teleosts (bony fish), but they also prey on cephalopods, and crustaceans. Both juveniles and sub-adults prey more on smaller octopi species, such as Octopus leteus and O. hawaiiensis, nocturnal octopi species, and eels than the adult Hawaiian monk seals. While, adult seals feed mostly on larger octopi species such as O. cyanea. Hawaiian monk seals have a broad and diverse diet due to foragingForaging
- Definitions and significance of foraging behavior :Foraging is the act of searching for and exploiting food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce...
plasticity
Phenotypic plasticity
Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship...
which allows them to be opportunistic predators that feed on a wide variety of available prey.
Mating and Reproduction
The Hawaiian monk seals mate in the water during their breeding season, which occurs between the months of December and August. Females reach maturity at age four and give birth to one pup a year. The Hawaiian monk seal fetusFetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
takes nine months to develop, with birth of the pups occurring in March and June. The pups usually weigh about 16 kg and are about 1 m long. Pups are born with a black coat which they shed at about six weeks and replace with a gray coat on the back and white on the belly. The pups are born on beaches and nursed by their mothers for about six weeks. After that time, the mother will desert the pup, leaving it on its own, and return to the sea to forage for the first time since the pup’s arrival.
Ecological Interactions
Tiger sharkTiger shark
The tiger sharks, Galeocerdo cuvier, is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as sea tigers, tiger sharks are relatively large macropredators, capable of attaining a length of over . It is found in many tropical and temperate waters, and is...
s and Galapagos shark
Galapagos shark
The Galapagos shark is a species of requiem shark, family Carcharhinidae, found worldwide. This species favors clear reef environments around oceanic islands, where it is often the most abundant shark species...
s are both predators of the Hawaiian monk seals.
Scars are found on many of the monk seals as a result of their encounters with these predators. Also, female monk seals have scars from aggressive male monk seals. Furthermore, a recent study showed that the monk seals are dying from a pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
in cat feces (toxoplasmosis
Toxoplasmosis
Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid family. Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself...
) that is carried to the ocean in polluted runoff and sewage water, which is a new threat to this endangered species. Over the past ten years, the cat parasite has killed at least four monk seals in the main Hawaiian Islands. In addition to toxoplasmosis, other pathogens have infected monk seals with leptospirosis
Leptospirosis
Leptospirosis is caused by infection with bacteria of the genus Leptospira, and affects humans as well as other mammals, birds, amphibians, and reptiles.The...
being one of the biggest concerns. Additionally, Hawaiian monk seals also have frequent human encounters from commercial fishermen and tourists.
Threats
Natural threats include mainly predation by sharks.Seal populations have declined rapidly in recent years due to the rapid spread of human activity to even the most remote and isolated areas in the Hawaiian Islands. In the nineteenth century, Hawaiian monk seals were clubbed to death by whalers
Whaling
Whaling is the hunting of whales mainly for meat and oil. Its earliest forms date to at least 3000 BC. Various coastal communities have long histories of sustenance whaling and harvesting beached whales...
and sealers
Seal hunting
Seal hunting, or sealing, is the personal or commercial hunting of seals. The hunt is currently practiced in five countries: Canada, where most of the world's seal hunting takes place, Namibia, the Danish region of Greenland, Norway and Russia...
for meat, oil and skin. U.S. forces hunted them during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
while occupying Laysan Island and Midway
Midway Atoll
Midway Atoll is a atoll in the North Pacific Ocean, near the northwestern end of the Hawaiian archipelago, about one-third of the way between Honolulu, Hawaii, and Tokyo, Japan. Unique among the Hawaiian islands, Midway observes UTC-11 , eleven hours behind Coordinated Universal Time and one hour...
.
As the result of human disturbances, ciguatera
Ciguatera
Ciguatera is a foodborne illness caused by eating certain reef fishes whose flesh is contaminated with toxins originally produced by dinoflagellates such as Gambierdiscus toxicus which lives in tropical and subtropical waters. These dinoflagellates adhere to coral, algae and seaweed, where they are...
poisoning, high male to female ratios occurred during the breeding season, and entanglement in fishing net
Fishing net
A fishing net or fishnet is a net that is used for fishing. Fishing nets are meshes usually formed by knotting a relatively thin thread. Modern nets are usually made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and...
s and debris have killed many animals. In the northwestern Hawaiian islands, starvation is a serious problem. Lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
s, the seals' preferred food other than fish, have been overfished and competition from other apex predators such as sharks, jacks
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
, and barracuda
Barracuda
The barracuda is a ray-finned fish known for its large size and fearsome appearance. Its body is long, fairly compressed, and covered with small, smooth scales. Some species could reach up to 1.8m in length and 30 cm in width...
s, leaves little left over for developing pups. The creation of Papahānaumokuākea Marine National Monument enclosing these islands may lead to more abundant food supplies.
In areas where male seals outnumber females, several males may compete for a single female, known as mobbing, often accidentally killing the female. Females of any age including pups can become targets.
These threats have taken a toll on the species. It has been nearly eradicated from the main Hawaiian Islands. The population there is approximately 150. It is currently found on Laysan
Laysan
Laysan , located northwest of Honolulu at N25° 42' 14" W171° 44' 04", is one of the Northwestern Hawaiian Islands. It comprises one land mass of , about 1 by 1.5 miles in size . It is an atoll of sorts, although the land completely surrounds a shallow central lake some above sea level that has...
, Midway
Midway Atoll
Midway Atoll is a atoll in the North Pacific Ocean, near the northwestern end of the Hawaiian archipelago, about one-third of the way between Honolulu, Hawaii, and Tokyo, Japan. Unique among the Hawaiian islands, Midway observes UTC-11 , eleven hours behind Coordinated Universal Time and one hour...
, Pearl and Hermes Atoll
Pearl and Hermes Atoll
The Pearl and Hermes Atoll , is part of the Northwestern Hawaiian Islands. Named after two English whaleships, the Pearl and the Hermes, that wrecked there in 1822, a few, small, sandy islands exist, contained within a lagoon and surrounded by a coral reef. These islands are devoid of vegetation,...
, French Frigate Shoals
French Frigate Shoals
The French Frigate Shoals is the largest atoll in the Northwestern Hawaiian Islands. Its name commemorates French explorer Jean-François de La Pérouse, who nearly lost two frigates when attempting to navigate the shoals...
, and Lisianski
Lisianski Island
Lisianski Island is one of the Northwestern Hawaiian Islands, with a land area of and a maximum elevation of above sea level. Honolulu is away, to the southeast. Linked to Lisianski are the extensive Neva Shoals...
.
In the summer of 2009, two monk seals were shot and killed.
Slowly, however, the monk seals are returning to the main Hawaiian Islands. Lone seals have been sighted in surf breaks and on beaches in Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
, Niihau
Niihau
Niihau or Niihau is the seventh largest of the inhabited Hawaiian Islands in the U.S. state of Hawaii, having an area of . Niihau lies southwest of Kauai across the Kaulakahi Channel. Several intermittent playa lakes provide wetland habitats for the Hawaiian Coot, the Black-winged Stilt, and the...
, Maui
Maui
The island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...
, O'ahu's Turtle Bay
Turtle Bay, O'ahu
Turtle Bay is located between Protection Point and Kuilima Point on the North Shore of the island of O'ahu in the U.S. state of Hawaii.-Geography and environment:...
, and even spotted on Waikiki beach on March 4, 2011, outside of the Moana Hotel
Moana Hotel
The Moana Hotel, also known as the First Lady of Waikīkī, is a famous historic hotel on the island of Oahu, located at 2365 Kalākaua Avenue in Honolulu, Hawaii. Built in the late 19th century as the first hotel in Waikiki, the Moana opened its doors to guests in 1901, becoming the first large hotel...
. They often leave the water haul out on busy tourist beaches, where they are vulnerable to disturbance. In early June 2010, 2 seals were seen hauled out on Oahu's popular Waikiki beach. NOAA has cultivated a network of volunteers who protect the seals while they bask or bear and nurse their young. In 2006, twelve pups were born in the main Hawaiian Islands, rising to thirteen in 2007, and eighteen in 2008. As of 2008 43 total pups have been counted in the main Hawaiian islands. Tiger sharks also prey on them which also damages the monk seal population.
NOAA is funding considerable research on seal population dynamics and health in conjunction with the Marine Mammal Center.
Endangered status
The Hawaiian monk seal is among the most endangered of all seal species, although its cousin species the Mediterranean monk sealMediterranean Monk Seal
The Mediterranean monk seal is a pinniped belonging to the Phocidae family. At some 450-510 remaining individuals, it is believed to be the world's second-rarest pinniped , and one of the most endangered mammals in the world.It is present in parts of the Mediterranean Sea and the eastern Atlantic...
(M. monachus) is even rarer, and the Caribbean monk seal
Caribbean Monk Seal
The Caribbean monk seal or West Indian monk seal is an extinct species of seal. It is the only seal ever known to be native to the Caribbean Sea and the Gulf of Mexico. The last verified recorded sighting occurred in 1952 at Serranilla Bank...
(M. tropicalis), last sighted in the 1950s, was officially declared extinct in June 2008. The population of Hawaiian monk seals is in decline. In 2010, it was estimated that only 1100 individuals remain. It is listed as critically endangered. The Hawaiian monk seal was officially designated as an endangered species on November 23, 1976, and is now protected by the Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
and the Marine Mammal Protection Act
Marine Mammal Protection Act
The Marine Mammal Protection Act of 1972 was the first article of legislation to call specifically for an ecosystem approach to natural resource management and conservation. MMPA prohibits the taking of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal,...
. Today, even though the islands are protected, many scientists believe that the effects of human activity along these fragile coastlines (and in the world at large) are still taking their toll
It is illegal to kill, capture or harass a Hawaiian monk seal.
To raise awareness for the species' plight, the Hawaiian monk seal was declared Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
's official State Mammal on June 11, 2008 by Lieutenant Governor James Aiona
James Aiona
James R. "Duke" Aiona, Jr. is an American politician who served as Lieutenant Governor of Hawaii from 2002 to 2010. He is of Hawaiian, Chinese, and Portuguese descent...
.
The multitude of factors that play a role in the limitation of population growth seen in the critically endangered Hawaiian monk seal can be seen as the primary natural facets and the anthropogenic impact of the past and present. Several natural factors affecting the recovery of the Hawaiian monk seal include the low genetic variability observed in populations, low juvenile survival rates, reduction of habitat/prey associated with environmental changes, increased male aggression, and subsequent skewed ratios amongst the sexes. Anthropogenic or human impacts to monk seals include hunting (during 1800s and 1900s), human disturbance, entanglement in marine debris, and fishery interactions.
Natural Factors
Of 18 pinnipedPinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
species, the Hawaiian monk seal has the lowest level of genetic variability. A study found that this low genetic variability is due to a population bottleneck
Population bottleneck
A population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing....
caused by intense hunting in the 19th century. This lacking in genetic variability reduces the species ability to adapt to environmental pressures and limits natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
thus increasing their risk of extinction. One such environmental pressure that may be detrimental to the monk seal would be the presence of an infectious disease;in such small populations the effects of a disease could be disastrous. One possible infectious agent affecting the overall health of the species could be from ciguatera
Ciguatera
Ciguatera is a foodborne illness caused by eating certain reef fishes whose flesh is contaminated with toxins originally produced by dinoflagellates such as Gambierdiscus toxicus which lives in tropical and subtropical waters. These dinoflagellates adhere to coral, algae and seaweed, where they are...
poisoning. Another possibility arises from postmortem examinations of seal carcasses revealing gastric ulcerations caused by parasites, which would negatively affect the health of the seal.
Additionally, low juvenile survival rates continue to threaten the species. High juvenile mortality is due to starvation, shark predation, and marine debris entanglement. A reduction in habitat and subsequently a reduction in prey abundance associated with environmental changes results in a decrease in seal populations due to starvation. The critical habitat is being lost due to erosion in the Northwest Hawaiian Islands, which is shrinking the islands/beaches and proving to be very problematic for the monk seal. Another huge contributor to the low juvenile survival rates is the predation from sharks. Most mature monk seals are scarred from previous encounters with sharks and many such attacks have been observed. Additionally, marine debris entanglement can result in mortality because the seals get trapped in debris such as fishing nets and cannot escape.
Furthermore, mobbing, a practice among the seals that involves a large number of seals attacking one seal in mating attempts, is responsible for many deaths especially to females. Mobbing leaves the targeted individual with many wounds that lead to septicemia and the seals then die from infection. In a study performed by Gilmartin et al., it was found that a small population of monk seals was more likely to experience a mobbing problem as a result of the increased male-biased sex ratio and male aggression. It was also observed that unbalanced sex-ratios were more likely to occur in slow-growing populations, therefore until the population reaches a large or rapidly growing population state, biased sex-ratios and mobbing will continue.
Anthropogenic Impacts
Human disturbances have had immense effects on the populations of the Hawaiian monk seal. Monk seals tend to avoid beaches where they are disturbed; after continual disturbance the seal may completely abandon the beach, thus reducing its habitat size, subsequently limiting population growth. Although the military bases from WWII in the Northwestern Hawaiian Islands have been closed down, minimal human activities can be enough to effectively disturb the species.Entanglement in marine debris is another huge impact from people that cause great damage to the seal populations, despite international law prohibiting the intentional discarding of debris from ships at sea. Monk seals have one of the highest documented rates of entanglement of any pinniped species; a huge problem that current studies indicate there is no sign of it abating in the future.
Marine fisheries can potentially interact with the monk seals via direct and indirect relationships. Directly the seal can become snared by fishing equipment, entangled in discarded debris, and even feed on fish refuse. While the possible indirect effects have yet to be documented, they include the effect overfishing may have on the prey abundance of the monk seal, negatively effecting the seal’s diet and habitat.
Identification and mitigation of these and other possible factors (e.g., disease) limiting population growth represent ongoing challenges and are the primary objectives of the Hawaiian monk seal conservation and recovery effort.
Conservation Methods
The goal of reversing population decline hinges on a comprehensive, scientifically sound characterization and mitigation of relevant natural and anthropogenic factors along with better understanding of the species' particular vulnerabilities.Public outreach and education remain the most powerful tools for promoting the conservation of the Hawaiian monk seal and its habitat. Human proximity and entanglement in marine debris kill many animals. For instance, large beach crowds and beach structures limit the seal’s habitat.
In 1909, President Theodore Roosevelt
Theodore Roosevelt
Theodore "Teddy" Roosevelt was the 26th President of the United States . He is noted for his exuberant personality, range of interests and achievements, and his leadership of the Progressive Movement, as well as his "cowboy" persona and robust masculinity...
created the Hawaiian Islands Reservation that included the Northwest Hawaiian islands. The Reservation later became the Hawaiian Islands National Wildlife Refuge (HINWR) and moved under the jurisdiction of the U.S. Fish and Wildlife Service (USFWS). This marine sanctuary greatly benefited the seals.
As anthropogenic impacts are reduced, natural factors affecting population growth must also be addressed.
Genetic data analysis is needed because identifying individuals genetically along with confirming maternity and paternity can provide information about male and female reproductive rates which are crucial to wildlife managers.
Protecting female pups
One key natural factor affecting the seal populations is the male-biased sex-ratio, which results in increased aggressive behaviors such as mobbing. These aggressive behaviors decrease the number of females in the population. Two programs effectively aid female survival rates.“Headstart” began in 1981, collected and tagged female pups after weaning, and placed them in a large, enclosed water and beach area with food and lacking disturbances. The female pups remain during the summer months, leaving at roughly age three to seven months.
Another project began in 1984 at French Frigate Shoals
French Frigate Shoals
The French Frigate Shoals is the largest atoll in the Northwestern Hawaiian Islands. Its name commemorates French explorer Jean-François de La Pérouse, who nearly lost two frigates when attempting to navigate the shoals...
. It collected severely underweight female pups, placed them in protective care and fed them. The pups were released as yearlings and relocated to the Kure Atoll
Kure Atoll
Kure Atoll or Ocean Island is an atoll in the Pacific Ocean beyond Midway Atoll in the Northwestern Hawaiian Islands at . The only land of significant size is called Green Island and is habitat for hundreds of thousands of seabirds...
.
Some habitats are better suited to increase survival probability making relocation a popular and promising method. Although no direct links between infectious diseases and seal mortality rates have been found, unidentified infectious diseases could prove detrimental to relocation strategies.
External links
- Hawaiian Monk Seal Recovery Program, NOAA Fisheries Service Protected Resources Division
- The Monachus Guardian
- NOAA Midway Island Captive Care & Release Project
- Kauai Monk Seal Watch website
- Monk Seal Video in Oahu
- http://www.mauimagazine.net/Maui-Magazine/Summer-2004/Watching-Out-for-Makana/"Watching Out for Makana" feature about Hawaiian monk seals on Maui by Hannah Bernard, Maui No Ka 'Oi MagazineMaui No Ka 'Oi MagazineMaui Nō Ka Oi Magazine is a bi-monthly regional magazine published by the Haynes Publishing Group in Wailuku, Hawaii.The phrase Maui nō ka ʻoi means "Maui is unparallel" in the Hawaiian language. Maui Nō Ka Oi Magazine features stories relating to the culture, art, dining, environmental issues,...
, Vol.8 No.2 (July 2004).] - Weekend Window to Niihau, Hawaii's 'Forbidden Island'
- Field notes and observations on Koki the monk seal born Hana October 9, 2009 by Dr. George R. Harker
- Monk Seal Foundation website