Protected Resources Division

population and threats

Population Size and Threats

Population Status/ Stock Assessment

population graphic

The prolonged and steep decline of the Hawaiian monk seal population has occurred more or less continuously since the 1950's. Although this decline (about 4% per year) does not bode well for species recovery in the short-term or even medium-term, there have been some relatively recent encouraging developments, including:

The best estimate of the current total Hawaiian monk seal population is 1,060 seals - 907 in the Northwestern Hawaiian Islands (NWHI), and 153 in the main Hawaiian Islands (MHI) (note: this estimate does not include Nihoa or Necker). Since 2001, the total abundance at the six main NWHI sites (French Frigate Shoals, Laysan, Lisianski, Pearl and Hermes, Midway and Kure) has been declining at an average annual rate of about 4.5%. The primary cause of the decline appears to be low juvenile survival in the NWHI, where less than 1 of every 5 seals survives to reproductive age.

population graph

The overall decline has been moderated by the increasing population of seals in the MHI. Although Hawaiian monk seals were only rarely reported in the MHI over most of recorded history, since 1990, an increasing number of seal sightings and births have occurred in the MHI. Sightings in the MHI increased from 77 individually identifiable monk seals in 2005 to 153 in 2010. This increase is due in part to intrinsic population growth, and also to the increased monitoring effort identifying individual seals. Documented annual births in the MHI have increased since the mid-1990s, with 25 births reported in 2010. The small but increasing population of seals in the MHI is perhaps the most promising aspect for Hawaiian monk seal recovery, but this growing seal population in areas that are heavily populated by humans is creating a new set of recovery challenges as discussed below.

Population Fact Sheet (May 2010, pdf 375kB)

Threats to Recovery

Despite the fact that Hawaiian monk seals are one contiguous species, the subpopulations in the NWHI and MHI face different threats. In the NWHI, primary threats include food limitation for juveniles, shark predation on juveniles, entanglement in marine debris, male seal aggression on females and juveniles, and shoreline habitat loss. Threats in the MHI include disease and various types of human-induced impacts, such as disturbance at haul-out areas, fishery interactions, feeding and other interactions that cause habituation to humans, and most recently, intentional killings.

Northwestern Hawaiian Islands

threats in the northwestern hawaiian islands

Main Hawaiian Islands

main hawaiian island threats

Threats Fact Sheet (May 2010, pdf 505kB)