Hawaiian Monk Seal

Llio holo l ka uaua--Dog that runs in rough water
By: Kian Jeffries

Source: Wikipedia, Hawaiian Monk Seal

What is this thing?
The Hawaiian monk seal is a rare marine mammal part of the "true seal" family, along with the Mediterranean monk seal and the, now extinct, Caribbean monk seal. The Hawaiian monk seal (HMS) is one of two mammal species native to Hawaii, with the other being the hoary bat. The HMS gets its name from the thick fold of skin around its neck, which resembles a monk's hood, and because it lives a reclusive life compared to other seals, who live in colonies. Hawaiian monk seals weigh an average of 375-450 pounds and are 7.0-7.5 feet in length. The life span of this seal is 25-30 years (National Wildlife Federation). As the name suggests, the HMS can be found exploring the Hawaiian Islands, specifically the Northwestern Islands.

The HMS spends approximately two-thirds of their time in the water, with the remaining time spent on the sandy Hawaiian shores. Monk seals breed offshore, then the female selects a site and gives birth to one offspring, typically between March or April (but births have been seen year round). The female is known to fast and strictly stay with her pup to nurse for 5-6 weeks. While the pup gains nearly 175 pounds during this period, the female looses 1/3 of her body mass. Contrary to their solitary nature, monk seals have been seen fostering other seals' pups. Breeding can get violent and even deadly for the female monk seal, because the male-dominated species will surround one female, known as "mobbing."

Monk seals' diet consists of fish, cephalopods (octopus, squid, etc.), and crustaceans (crab, lobster, shrimp). Most of their prey is caught in shallow waters, but bradycardia--the ability to slow the heart rate 8 times less than normal to decrease the oxygen level needed-- allows them to dive 900 feet below the surface.

Distribution of HMS

Source: NOAA Fisheries

Population

Hawaiian monk seals, as mentioned before, are native to Hawaii. A majority of the seals live in six subpopulations in the Northwestern Hawaiian Islands (NWHI). A 2011 estimation revealed only 1,100 monk seals remained, with a decline rate of nearly 4%. Within the last decade, monk seals have had a steady decline rate of 3.4% (ESA Recovery Plan, ecos.fws.gov) Each of the six subpopulations have their own ecological pressures, which is leading to this decreasing population. A small number (<150) of HMS's are located near the main islands of Hawaii, with pup seals having a higher survival rate than those around NWHI. Monk seals typically stay at the island in which they were birthed.

Below is a projection of the HMS population by 2030. As you can see, in 15 years, the monk seal could be near extinction. Population levels in the NWHI will drop below those near the main islands.

Source: NOAA Fisheries

Population Projection for HMS through 2030

Source: NOAA Fisheries

The Hawaiian monk seal was listed as an endangered species under the ESA on November 23, 1976. There have been numerous recovery plans and revisions made by the National Marine Fisheries Services, with the most recent in 2007. Despite years of recovery effort, the HMS is still on the decline for numerous reasons.

Critical Threats
a) Food Limitation-- The Hawaiian monk seal's greatest threat is thought to be a limited food supply. Pup and juvenile seals are drastically smaller in size, which can be attributed to shortage of food, amongst other factors. This is a problem on the NWHI, not the main islands, but with most of the population being in the NWHI, this is a critical threat. There has been a decline in birth rates, which could also be contributed to the food limitation. It is difficult to pinpoint a food shortage, because the HMS has a wide geographic distribution, and there is high species diversity in their prey. A food shortage, though, could be forcing monk seals to spend more time looking for prey, which increases their chances of entanglement or predation.

Source: NOAA, Published in National Geographic

b) Entanglement-- The HMS faces the threat of entanglement from fishing nets / lines and other objects, such as life vests that have been discarded in the ocean. Between 1982 and 2006, 268 entanglements were documented, with 118 occurring because of fishing gear (ESA Recovery Plan, ecos.fws.gov) Pups have the highest rate of entanglement. Between 1982 and 1988, "pups comprised 11% of the population, yet accounted for 42% of the observed entanglements" (ESA Recovery Plan, ecos.fws.gov). If the seal cannot free itself or is not freed by researchers, it will suffer from drag while swimming and hunting for prey. They can also suffer from wounds that can become infected and lead to more serious issues, severance of vital tissues, or death by strangulation or drowning. Entanglement also makes it difficult for monk seals to protect themselves from their third critical threat: predation.

Injury from Tiger Shark

Source: http://www.underwaterkwaj.com/

c) Predation-- Shark predation has been a large contributor to the decline of the monk seal population, specifically in the subpopulation called the French Frigate Shoals (FFS). From 1989-2010, the population of the HMS decreased by 75% in the FFS. It is estimated that 30% of all pups are killed by sharks (NOAA Fisheries). Sharks were recorded to have caused 18-28 mortalities per year between 1997-1999.  Aside from FFS, shark predation has not been observed as a significant issue.

d) Other threats-- There are other serious, but not crucial, threats that face the HMS. These include infectious diseases, male aggression, habitat loss, and fishery/human interaction. The habitat loss is due to environmental factors such as rising sea level. In the future, this could impact the HMS because it would reduce their resting and pupping habitat.

Source: Marine Mammal Center

Steps to Recovery
A previous recovery plan for the HMS addressed the critical threats discussed above and has proved to be successful in preventing the extinction of this species. These included actions such as reducing disturbances on key breeding beaches, reducing death caused by male aggression and shark predation, and reducing the impact of entanglement. Programs that aid in the disentanglement of monk seals are ongoing, along with the continued removal of hazardous debris. There has also been significant efforts to eliminate interaction with commercial fisheries. While these actions are still being used to aid in the recovery of the HMS, they were not enough to remove the species from the status of extremely critical.

The most recent recovery plan incorporated new actions that will further assist in this effort. The main focus is an increase in the number and survival of breeding female seals. This is being done through protection of the HMS prey base and habitat, and protection from male aggression and shark predation. Food limitation is thought to be a large threat, but research is being conducted to explicitly link survival to prey abundance. Research is also being done to decipher why the juvenile survival rate is so low and how that can be solved.

Efforts are being expanded on the Main Islands, where the HMS population is rising. All parties are coming together to coordinate their efforts to ensure the natural recovery of this species. Back in the NWHI, more attention is being paid to sharks, including monitoring and removing problem sharks.

Ongoing actions are being taken. In 2014, NOAA Fisheries received a new ESA permit to continue in the recovery of the Hawaiian monk seal and said "we will continue to work with our partners to implement priority recovery actions to accelerate monk seal recovery" (NOAA Fisheries).

This issue may seem outside your sphere of influence, but there are steps to take to aid in recovery. If you happen to stumble upon a Hawaiian monk seal, please give them their space, do NOT feed them, and report the sighting. If you will be fishing in the NWHI area, or any area for that matter, use barbless circle hooks. If you would like additional information, any of the links below are great sources. The full recovery plan can be read in detail from: http://ecos.fws.gov/docs/recovery_plan/hawaiianmonkseal.pdf

Thank you, for reading, and feel free to share!

Kian Jeffries
California Polytechnic State University, San Luis Obispo

Source: NOAA Fisheries

Works Cited

"Hawaiian Monk Seal." The Marine Mammal Center :. N.p., n.d. Web. 02 Dec. 2015.

"Hawaiian Monk Seal Population at a Glance." NOAA PIFSC. N.p., n.d. Web. 02 Dec. 2015.

"Hawaiian Monk Seal." Wikipedia. Wikimedia Foundation, n.d. Web. 02 Dec. 2015.

"Hawaiian Monk Seal." Wildlife. National Wildlife Federation, n.d. Web. 30 Nov. 2015.

National Marine Fisheries Service. "Recovery Plan for Hawaiian Monk Seal." U.S. Fish and Wildlife         Service (n.d.): n. pag. Aug. 2007. Web. Nov. 2015.

"Shark Predation." NOAA Fisheries, n.d. Web. 30 Nov. 2015.