The Hawaiian Monk Seal: An Endangered Species

 

The Hawaiian monk seal (Neomonachus Schauinslandi) is an endemic species located on the Hawaiian Islands. It has the following taxonomy: Kingdom: Animalia, Phylum: Chordata, Class: Mammalia, Order: Carnivora, Family: Phocidae, Genus: Neomonachus, and Species: Schauinslandi (fisheries.noaa.gov).  It is found predominately on the Northwest Hawaiian Islands, with a smaller population located on the main islands.

The monk seal arrived at the Hawaiian Islands anywhere from 3.5 to 11.6 million years ago.  They are believed to have entered from the east via a passage way in Central America (fpir.noaa.gov).  The animals were hunted aggressively in the 19th century for their fur.  Since then, there population has not been able to recover.  The monk seals face a number of obstacles to survival.  Its population is still declining, as there were an estimated 1,112 remaining in 2015.

Historically, its geographic range has been within the U.S. waters near the Hawaiian Islands.  They can be found on the isolated beaches of the northwestern islands.  They spend much of their time at sea near coral reefs.  The seal’s habitat also consist of submerged sea banks, atolls, and other areas offshore.  The monk seal typically forages for food at a depth of 60-300ft. deep (fisheries.noaa.gov).

During breeding season, the monk seals are located on the sandy beaches of Hawaii.  They prefer remote and secure locations when nursing their pups, which lasts a month until they return to the sea.  The life span of a Hawaiian monk seal is 25-30 years.  They mature at the age of five, and can grow up to 7.5 feet and weigh 400lbs.  An interesting feature of the seal is they are born black, but grow a silver coat later in life.  The monk seal is considered a “benthic forager” which eat fish, eels, octopus, and crustaceans (fisheries.noaa.gov).

There are several reasons for the Hawaiian monk seal’s population has declined at such a rapid rate over the past few decades.  First of all, the human population on the islands has disturbed the animals’ natural habitat.  The seals often die after getting caught in fishing nets, and there is a decrease in food available which might be attributed to overfishing in the area.  The seals have faced difficulty in finding sufficient food due to competition from other predators as well.  Also, the monk seal is a source of prey for sharks which adds to its loss in numbers.

Genetic variability is low among the Hawaiian monk seals, which has added to the species’ difficulty in recovering from its endangered status.  This is compounded by the fact that subpopulations fail to migrate or interact with populations of differing islands.  This has caused inbreeding which carries with it a host of negative consequences.  Genetic diversity helps a species to recover by promoting disease resistance and adaptability to a changing environment.  On the other hand, a lack of diversity increases a chance for disease and reproductive failure (Kretzmann 482-483).

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Inbreeding occurs when the number of potential mates is low, and it carries with it a number of concerns.  When a species is facing extinction, the absence of genetic diversity can compound its struggle for survival.  DNA testing of the monk seal has shown that its genetic diversity is extremely low.  Because of this, an outbreak of an infectious disease could possibly cause the Hawaiian monk seal to become extinct (Kretzmann 487).  If the seals were to breed with populations from differing islands, it could hypothetically increase their chance for survival.

Mobbing, or the aggressive behavior exhibited by male seals, often results in the death of a female or young seal.  It occurs when a group of males attempt to mate with one female and end up attacking the female.  The resulting injuries can lead to infection or death.  This is causing slower development of the seals’ population.  It is found that in groups of smaller populations with slower growth rates, instances of this behavior are higher.  It is thought that mobbing is a learned behavior that may take time to be overcome.  Intervention can be used to decrease mobbing behavior, such as removing a set number of males from an area where there is an unequal gender ratio (Starfield and Roth 166, 169).

There is currently action being taken to help the species recover.  The Hawaiian Monk Seal Captive Care Workshop was created to halt the population decline and help it to recover.  The organization believes that an annual reduction in population of 3.9% is due to the poor survival rate of juvenile seals.  By supporting captive seals through rehabilitation, nutrition, and relocation, the group hopes to increase survival.  It also advocates for other methods of helping the species, such as disentangling seals caught in fishing nets and removing debris from its habitat (Baker and Littnan 11).

Other methods include removing sharks from the seals’ habitat, or relocating pups to areas where there is a lower risk from predators.  Captive care and release helps undernourished or ill pups that might otherwise die.  Once they are healthy, the young seals are relocated to an area where they will have a better chance of survival (Baker and Littnan 11, 12).  It has been found that a high rate of seal pups die shortly after being weaned from the mother.  The mother will leave the pup after one month of nursing, and if the pup is unable to find sufficient food, it faces starvation and death.  The importance of the conservation efforts by these captive care and release programs cannot be understated.

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Since the Hawaiian monk seals have low genetic variability, they are more susceptible to disease.  It is thought that another species, the Caribbean monk seal (Neomonachus Tropicalis), had a susceptibility for disease which likely hastened its extinction.  The morbillivirus is of particular concern for the Hawaiian monk seals.  The morbillivirus is a string of viruses that include the measles, which can be spread quickly and easily.  Once a seal has become infected with the virus, the lungs and brain are affected, which can lead to death in as little as 5 days.  The disease has already killed thousands of Atlantic seals and dolphins.  Since the seals have no immunity to these viruses, scientists have taken action to create and administer a vaccination (Rogers).

Once scientists found a suitable vaccine, they began to administer it to the seals in 2015.  The vaccination process begins with a single injection, followed up with a booster shot one month later.  As of September 2016, 43 Hawaiian monk seals have received the vaccination.  The group of scientists (HMSRP) administering the shots hope that this project will be successful and grow.  The Hawaiian Monk Seal Research Program is also involved in other interventions such as removing seals from fishing nets and hooks, rehabilitating malnourished pups, and relocating seals to higher survival areas.  Their efforts have slowed the population’s decline by over half in the past 3 decades (Rogers).

While the monk seal once had instrumental value, and were hunted for their furs, this led to the near extinction of the species in the early 1900’s.  Since the seal is no longer used for human purposes, it is now appreciated mainly for its intrinsic beauty.  Intrinsic beauty is something that can be valued for its own sake.  The monk seal is a rare animal that can be appreciated for its uniqueness, and has been an important aspect of the Hawaiian Islands for over 3 million years.

The Hawaiian monk seal is also important to other species and the area’s ecosystem.  They are an “apex predator” and play an important role in keeping a number of prey from becoming overpopulated.  Therefore, they create a balance needed for in maintaining a diverse and stable ecosystem (Muneoka).  This is a significant reason for the conservation of the Hawaiian monk seals.

The Hawaiian monk seal has faces so many obstacles over the past century, yet it has been able to survive in spite of these.  The most alarming problem that the seals face is lack of food.  The juvenile seals are facing a continuing threat of starvation, and they are in constant competition with fisheries and other predators.  Protected areas for the seals have been used in the past, and expanding these will likely help.  It will not only increase food supply for the seals, but will also prevent them from getting caught by fish hooks or nets.

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Until there is a greater supply of food for the monk seals, efforts in capturing and rehabilitating the young pups is important.  Also, once they seals are at a healthier weight, they can be placed in an area where there is a higher source of food and increased chance of survival.  Relocating seals is also helpful in increasing genetic diversity, which will help in the species ability to fight disease.  Inoculation of the monk seal is also a good attempt at decreasing the seals vulnerability of disease.

One other concern, mobbing, is a factor that is decreasing the chance of the seals’ survival.  Interventions, such as removing males from areas where there is an imbalanced ratio of male to female, are helpful.  With all of these efforts, and the noble concern of the people involved, the Hawaiian monk seal is beginning to see a brighter future.

The population of monk seals has rising 3% annually over the past 3 years.  As of January, 2017, there is an estimate of 1,400 Hawaiian monk seals.  This is a great improvement, considering there were 1,112 seals in 2015.  Interestingly, the state of Hawaii has dedicated 2017 as the Year of the Monk Seal.  In conclusion, with the continuing hard work of the hard working people involved to save the Hawaiian monk seal, there is great hope for the species survival in the future.

Works Cited

“Hawaiian Monk Seal (Neomonachus schauinslandi).”

http://www.fisheries.noaa.gov/pr/species/mammals/seals/hawaiian-monk-seal.html.  Web. 16 Feb. 2017.

“Historical Timeline of the Hawaiian Monk Seal.”

http://www.fpir.noaa.gov/Library/PRD/Hawaiian%20monk%20seal/HMS_natural_history_timelineWEB.pdf.  Web. 16 Feb. 2017.

Schmelzer, Isabelle. “Seals and Seascapes: Covariation in Hawaiian Monk Seal Subpopulations and the Oceanic Landscape of the Hawaiian Archipelago.” Journal of Biogeography 27.4 (2000): 901-914. Academic Search Complete. Web. 16 Feb. 2017.

Kretzmann, Maria B., et al. “Low Genetic Variability in the Hawaiian Monk Seal.” Conservation Biology, vol. 11, no. 2, 1997, pp. 482-490., www.jstor.org/stable/2387621.  Web. 16 Feb. 2017.

Starfield, Anthony M., et al. “‘Mobbing’ in Hawaiian Monk Seals (Monachus Schauinslani): The Value of Simulation Modeling in the Absence of Apparently Crucial Data.” Conservation Biology, vol. 9, no. 1, 1995, pp. 166-174., www.jstor.org/stable/2386398.

Baker, Jason and Littnan, Charles.  “Report of the Hawaiian Monk Seal Captive Care Workshop, Honolulu, Hawaii, June 11-13, 2007.”  Pacific Islands Fish. Sci. Cent., Natl. Mar. Fish. Serv., (2008).

Rogers, Kim. “Why Rare Hawaiian Monk Seals Are Lining Up to Get Their Shots.”  Smithsonian (2016).  http://www.smithsonianmag.com/science-nature/researchers-are-vaccinating-wild-marine-species-first-time-180960479/.  Web. 17 Feb. 2017.

Muneoka, Lauren.  “Why Care About Monk Seals?”  Kahea (2011).  http://kahea.org/blog/why-care-about-monk-seals.  Web. 20 Feb. 2017.


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