Contingency Plan for Hawaiian Monk Seal Unusual Mortality Events

4
evaluations) are performed in the field; these preliminary findings, as well as descriptions
of gross lesions or clinical signs observed, are reported to the Monk Seal Assessment
Program and Monk Seal Health and Disease Program. These measures increase the
likelihood of timely detection of an unusual mortality event, allowing a response to be
mounted within the field season if deemed appropriate.
Known causes of mortality in Hawaiian monk seals include emaciation of juveniles,
tiger and Galapagos shark attacks, male aggression (individual and multiple), deleterious
fisheries interactions, and entanglement in marine debris (Balazs and Whittow, 1979;
Kenyon, 1981; Henderson, 1985, 1990; Alcorn and Kam, 1986; Banish and Gilmartin,
1992; Hiruki et al., 1993a, 1993b; Nitta and Henderson, 1993; Starfield et al., 1995).
Disturbance of pregnant or nursing females likely causes them to desert preferred
pupping beaches, resulting in decreased pup survival (Kenyon, 1972; Kenyon, 1981).
Maximum age is believed to be 25-30 years, but few seals live this long (NMFS,
unpublished data).
The influence of disease on monk seal populations is not well understood, but is an
active area of research (Aguirre et al., 1999; Aguirre, 2000; Appendix A, Hawaiian Monk
Seal Specimen Collection Protocol and Appendix B, Hawaiian Monk Seal Necropsy
Protocol). Infectious and noninfectious diseases have been reported in Hawaiian monk
seals but do not appear to be impeding population recovery: all wild seals carry parasites;
dental and skeletal abscesses and pathology were the apparent causes of death in one
aged seal; and biotoxins may pose a serious risk (Golvan, 1959; Rausch, 1969; Kenyon
and Rauzon, 1977 [cited in Kenyon 1981]; DeLong, 1978; DeLong and Gilmartin, 1979;
Gilmartin et al., 1980; Whittow et al., 1980; Dailey et al., 1988). Of the 15 Marine
Mammal Unusual Mortality Events (UMEs) occurring in other marine mammals species
since 1992 (Dierauf and Gulland, 2001: 72-73, Table 1), infectious diseases and biotoxins
were the most common diagnoses (five cases each). Other factors implicated in UMEs
included fisheries interactions, ship strikes, and large-scale decadal changes in oceanic
productivity (Polovina et al., 1995).
In a recent review of emerging and resurging diseases in marine mammals, Miller et
al. (2001) describes three ways in which wildlife species may be exposed to emerging
diseases (newly evolved or newly identified as pathogens), all three of which are
applicable to Hawaiian monk seals. The first is exposure via spillover from domestic
species or humans. Many recent reports of transmissible diseases in marine mammals
have included organisms traditionally associated with domestic animals and humans
(e.g.; Brucella sp., Ewalte et al., 1994; Ross et al., 1994; Jepson et al., 1994;
Mycobacterium bovis and M. tuberculosis, Forshaw and Phelps, 1991; Cousins et al.,
1993; Woods et al.; 1995; Bernardelli et al., 1996). The second method of exposure is via
rehabilitation or translocation of animals (e.g., Stamper et al., 1998, reports the possible
spread of leptospirosis from skunks to rehabilitating harbor seals). The third way that
wildlife species may become exposed to emerging diseases is through the effects of
environmental phenomena such as El Niño and large-scale climate change on the
proliferation or spread of infectious organisms (Fauquier et al. 1998; Harvell et al., 1999;
Reddy et al. 2001). Another source of exposure to infectious diseases in Hawaiian monk