Abstract

The Hawaiian monk seal (Monachus schauinslandi, HMS), a species approximately 12 million years old, is in crisis. One of two extant tropical phocids, the HMS population has declined almost 70% since 1958. Currently, there are approximately 1,200 individuals, and numbers have continued to decline nearly 4% annually since the late 90's. Poor juvenile survival over the last ten years has resulted in poor recruitment and subnormal pupping rates. Pup production projections are poor. In 2007 there were approximately 151 known pups. In ten years it is estimated that there will be approximately 70 pups born to the six Northwestern Hawaiian Island (NWHI) subpopulations, falling to less than 40 in twenty years.

Current factors influencing juvenile survival include starvation, apparent inability to compete with other predators for reduced food resources, and shark predation at French Frigate Shoals. Marine debris entanglement rates for HMSs are among the highest compared to other pinnipeds, and juveniles are the most common of age classes involved. Male aggression resulting in drowning and lethal wounds has diminished but remains a significant factor in the survival of juveniles.

In stark contrast to the six subpopulations in the NWHI, a seventh subpopulation in the Main Hawaiian Islands (MHI) appears to be increasing due mainly to improved pupping rates. Axillary girths at weaning, a good measure of maternal investment, are the highest of any region inhabited by HMSs. However, there is concern regarding potential new pathogens. As HMSs re-colonize the MHI, they are exposed to old as well as potentially new pathogens for the first time as a species. Human, pet, livestock, feral and wildlife pathogens are ubiquitous throughout the MHI.

Investigations into HMS genetics identify an unusually low genetic diversity and a nearly unvaried major immunohistocompatibility complex. This geographically isolated, genetically "bottlenecked" population is serologically naive and ill prepared to respond to new disease threats. Although there are great health risks to HMS in the MHI, this habitat may represent the most promising hope to avoid extinction.