TRUE SEALS

Hawaiian Monk Seal (Neomonachus schauinslandi)

The Hawaiian Monk Seal (Neomonachus schauinslandi) is a monk seal that is endemic to the Hawaiian islands. It was recently classified as sufficiently different in genus from the Mediterranean Monk Seal (Monachus monachus) and put in a new category with the (now extinct) Caribbean Monk Seal (Neomonachus tropicalis). N. schauinslandi itself is classified as Endangered by the IUCN. Estimated population size = 1,209.
N. schauinslandi are a true seal of a fairly large size (males ♂ up to 2.1 m long/ 180 kg, females ♀ up to 2.4 m/ 270 kg). They have long bodies, relatively long necks, long hind flippers, and short fore flippers. Their heads are broad and round with a small, flat crown, and a rounded, thick-lipped muzzle with fleshy whisker pads. Like M. monachus they have upward opening nostrils. Colouring of male N. schauinslandi is often shades of brown, while slate grey and silver is more common in females. However, all can appear dark to black, or even silvery, underwater. Patterning is often non existent or minor, consisting of subtle spotting. Female monk seals have 4 nipples, unlike the usual 2 in most phocids.
Feeding behaviour:
N. schauinslandi prey on a range of (mostly) benthic creatures including bony fish, crustaceans, and cephalopods, which are foraged from the shallow sea floor around atolls and reefs. They generally don’t dive to great depths when feeding although they are capable of reaching at least 500 m. An opportunistic feeding strategy means they will take advantage of many different species of prey, but studies have found a high intake of eels, flatfish, reef fish, lobster, crab, shrimp, and octopus.
Breeding behaviour:
Sexual maturity – males ♂ 5-8 years old/ females ♀ 4-7 years old.
Mating between N. schauinslandi occurs in the water, and males may gang together and be particularly aggressive with their rising testosterone levels, which has resulted in the death of females and juveniles who have been mobbed. The breeding strategy is polygyny and gestation lasts just under a year, around 11 months. Just like other monk seals, N. schauinslandi may give birth all year round, however, the peak birthing time is the summer, from March to August. Pupping usually takes place on shallow, sandy beaches, and these usually solitary seals will gather in loose groups at this time. Nursing of the black-coated youngsters continues for 6 weeks, during which time the mother will fast and the pup’s coat will be shed, making way for a silvery-grey juvenile pelt.  At weaning the pup will be left to survive on its reserves, before it learns to feed. The adults will undergo their annual moult (which is termed a “catastrophic moult” in monk seals as it includes fur and the top layer of skin) from April-September, post-weaning. Life span for N. schauinslandi is around 30 years.
N. schauinslandi do not have any subspecies, and in fact genetic diversity across their entire range is said to be very low.

Photo: NOAA

Previous: Mediterranean Monk Seal

Next: Northern Elephant Seal