The Hawaiian monk seal

In honor of endangered species day this year (May 21, 2021), here is some information on one of the most endangered seal species, the Hawaiian monk seal.

The Hawaiian monk seal is a species of seal that lives in the Hawaiian archipelago, mostly the Northwestern Hawaiian islands. It is called a “monk” seal because its folds of skin looks like a monk’s cowl and because it does not travel in groups. They are also unique because most seals live in cold waters, while the Hawaiian monk seal lives in tropical waters, among coral reefs. Hawaiian monk seals are one of the most endangered animals in the world, with a population of 1400. The only other monk seal in the world is the mediterranean monk seal, which is also endangered. The Caribbean monk seal is now extinct.

Left: the range of the Hawaiian monk seal. Most are found in the remote Northwestern Hawaiian islands, though a population of 300 can be found in the main Hawaiian islands.

Life cycle

Hawaiian monk seal pups are born with a dark fur color that gets lighter as they grow older. They are born around March through June. The mother seal stays with its pup for around 5 weeks and leaves it alone afterwards. Interestingly, a mother seal may sometimes adopt another pup.

At least once a year, monk seals will molt their fur, similar to a snake shedding its outer skin. This is because algae can grow on their fur. When a seal doesn’t molt their fur for a long enough time, it may even have a green tinge to it due to algae.

A Hawaiian monk seal is capable of living up to 25-30 years of age; however, they rarely get that old. Most seals are mature when they are 5-6 years of age. They spend most of their lives in water, feeding on fish in coral reefs, and come up to land to pup or rest.

Most monk seals are about 2 meters in length. Unlike other seal species, females are slightly larger than the males.


Unlike other endangered species, Hawaiian monk seals don’t have a single great threat. Instead, they have multiple small threats which makes conservation less easy because efforts have to be spread out instead of concentrated into one area, such as reducing getting caught in nets. Here are a few of the threats to their population:

  • Habitat loss from climate change- a few atolls in the Northwestern Hawaiian Islands are very low to begin with, and rising sea levels makes the islands smaller. Seals don’t have space to rest or to pup.

  • Shark predation- since the 1990s, the Galapagos shark has displayed atypical behavior by feeding very close to beaches and lowering the survival rate of pups

  • Entanglement- Hawaiian monk seals have the highest entanglement rate out of any pinniped (seal/walrus) species.

  • Intentional killing- a few dead seals are found every year with bullet wounds

  • Toxoplasmosis, a disease caused by a parasite coming from cat feces. There have been 13 known deaths from this disease, though there could be a lot more. Scientists have also been watching for morbillivirus, a disease that has not been seen in Hawaiian monk seals but could cause a huge decline since they don’t have antibodies. 700 Hawaiian monk seals have been vaccinated against it.

  • A low juvenile survival rate- this could be caused by limited food intake

History of conservation

The Hawaiian monk seal was hunted heavily in the 1800s. The sharpest decline in their population was around the 1980s, when the first year pup survival rate at the French Frigate shoals colony dropped from 80-90% to 15%. This drop was due to many reasons, including lobster fishing (which they prey on), and loud military and coastguard activities.

However, the Hawaiian monk seal population has been growing the past few years. Estimates say that 30% of the current population would be dead if not for conservation efforts. From 2013 to 2019, the population has increased steadily at 2% per year. The main concern currently would be a lack of genetic diversity.


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