Hawaiian Monk Seal Population at a Glance
The Hawaiian monk seal, one of the rarest pinniped species on Earth, was listed as Endangered under the US Endangered Species Act (ESA) in 1976. The NWHI population has declined 3.4% annually over the past decade. In 2011, the total minimum abundance of Hawaiian monk seals was estimated at 1,100 animals throughout the Hawaiian Archipelago.
The majority of the population (ca. 90%) is distributed throughout the remote islands and atolls of the Northwestern Hawaiian Islands (NWHI) within the Papahānaumokuākea Marine National Monument (PMNM). Each island contains a semi-isolated subpopulation of seals that face unique ecological pressures and conditions. While fishing pressure and human activity have been minimized within this vast marine environment, the population as a whole continues to decline.
Conversely, in 2011 a minimum of 150 seals resided in the main Hawaiian Islands (MHI) population that has slowly increased over the past ten years. Despite high levels of human activity around the MHI, monk seals appear to be in good physical condition and survival rates of pups are much higher than those in the NWHI.
The demographics of the monk seal populations in the NWHI and MHI are strikingly different. Seals residing in the NWHI have decreased survival rates, reproductive success, and overall body condition compared to those of the MHI. A variety of physical and environmental factors can account for these differences, and necessitate specific conservation and recovery strategies for each area.
Estimated Hawaiian Monk Seal Population Size by Island
|Location||Estimated 2011 Population Size1|
|Pearl and Hermes Atoll||181|
|French Frigate Shoals||190|
|Main Hawaiian Islands||>150|
Monk Seal Range and Movements
In the Northwestern Hawaiian Islands, there are 8 discrete monk seal subpopulations from Nihoa Island to Kure Atoll (excluding Gardner Pinnacles and Maro Reef), a distance of 2000 km (1,243 miles). A small number of seals are seen on each of the 8 main Hawaiian Islands, and births have been documented on every island except for Lanai. A few monk seals have been sighted at Johnston Atoll and a birth was documented in 1969. Hawaiian monk seals tend to remain at their natal (birth) island for life; however, some move between or among major population centers. A comprehensive review and analysis of monk seal movements is currently being conducted.