George A. Antonelis

INFECTIOUS DISEASE MONITORING OF THE ENDANGERED HAWAIIAN MONK SEAL

As part of conservation efforts between 1997 and 2001, more than 25% (332 animals) of the endangered Hawaiian monk seal (Monachus schauinslandi) population was sampled in the northwestern Hawaiian Islands. Serum samples were tested for antibodies to viruses, bacteria, and parasites known to cause morbidity and mortality in other marine mammal species. Antibodies were found to phocine herpesvirus-1 by using an enzyme-linked immunosorbent assay, but seropositive results were not confirmed by virus neutralization test. Antibodies to Leptospira bratislava, L. hardjo, L. icterohaemorrhagiae, and L. pomona were detected in seals from several sites with the microagglutination test. Antibodies to Brucella spp. were detected using 10 conventional serologic tests, but because of inconsistencies in test results and laboratories used, and the lack of validation by culture, the Brucella serology should be interpreted with caution. Antibodies to B. canis were not detected by card test. Chlamydophila abortus antibodies were detected by complement fixation (CF) test, and prevalence increased significantly as a function of age; the low sensitivity and specificity associated with the CF make interpretation of results difficult. Antibodies to Toxoplasma gondii and Dirofilaria immitis were rarely found. There was no serologic evidence of exposure to four morbilliviruses, influenza A virus, canine adenovirus, caliciviruses, or other selected viruses. Continuous surveillance provides a means to detect the introduction or emergence of these or other infectious diseases, but it is dependent on the development or improvement of diagnostic tools. Continued and improved surveillance are both needed as part of future conservation efforts of Hawaiian monk seals.

Effects of El Niño on the Foraging Energetics of the California Sea Lion

For a marine mammal foraging on widely dispersed prey items, the distribution and availability of prey and its species composition determine the rate of energy expenditure and acquisition. Models of central place foraging, optimal diet choice, and maximization of energy intake have attempted to predict how an animal should behave under a given set of circumstances (Charnov 1976; Dunstone and O’Connor 1979; Orians and Pearson 1979; Pyke 1984; Kramer 1988). However, few studies have documented how the rate of energy acquisition is modified when environmental circumstances change dramatically during a catastrophic event, such as the 1982/83 El Nino (EN).

Effects of the 1982–83 El Niño on Several Population Parameters and Diet of California Sea Lions on the California Channel Islands

Prior to the 1982–83 El Nino, California sea lion (Zalophus californianus) populations in the California Channel Islands were recovering from low abundance levels that resulted from unregulated exploitation and indiscriminate killing which began in the 1800s and continued through the late 1930s (Bonnot 1937; Bartholomew 1967; Stewart et al., in press). There has been an increasing trend in sea lion abundance on the California Channel Islands since 1958 (Bartholomew 1967; Odell 1971; Le Boeuf and Bonnell 1980; Stewart et al., in press). Based upon counts of pups born between 1971 and 1981, the sea lion population at San Miguel Island increased at about 5% annually (DeMaster et al. 1982). The population in the Channel Islands is estimated to number 87 000 animals (Boveng 1988).

Effects of El Niño 1983 on the Foraging Patterns of California Sea Lions (Zalophus californianus) near San Miguel Island, California

During the 1983 El Nino event, California sea lions (Zalophus californianus) and Galapagos fur seals (Arctocephalus galapagoensis) responded to the reduction in food availability by extending their foraging trips to sea and delivering less milk to their pups (Trillmich and Limberger 1985; Ono et al. 1987). These observed changes likely reflected a change in foraging tactics as animals attempted to compensate for a reduced food supply. The manner in which these foraging patterns were altered, however, still remains unclear.

Recovery of the Hawaiian Monk Seal (Monachus schauinslandi): A Review of Conservation Efforts, 1972 to 2010, and Thoughts for the Future

The Hawaiian monk seal is one of the world’s rarest marine mammal species and is listed as depleted, endangered, and critically endangered based on national and international criteria. Although its precarious status was already recognized by the 1950s, it was not until the 1970s that direct protection was afforded to monk seals by U.S. legislation. Many important actions were taken to try and recover the population during the following four decades, including developing a population monitoring program; controlling impacts of military facilities in the Northwestern Hawaiian Islands (NWHI); managing fisheries to reduce their impacts; removing marine debris; and responding to other issues, including die-offs, inadequate nutrition, aggression by male seals, and shark predation. Recently, monk seals have reoccupied the main Hawaiian Islands (MHI). While this may be good news for their recovery, the MHI are well-populated by humans and significant management issues have appeared as seal numbers have increased. In spite of all that has been done, Hawaiian monk seals are likely to go extinct unless current conditions change. At this time, the most crucial needs for the recovery are (1) maintaining an adequate research and management program throughout the Hawaiian Archipelago; (2) continuing to minimize all sources of mortality; (3) promoting an increase in the number of monk seals in the MHI; (4) considering bold actions that could create more favorable conditions for seals in the NWHI; (5) ensuring that bureaucratic requirements and processes do not impede recovery actions; and (6) designing, funding, and implementing a set of actions that will stop the Hawaiian monk seal’s decline toward extinction and recover the population sufficiently so that it can be removed from the Endangered Species Act’s list of endangered species.

Gastrointestinal Helminths in the Hawaiian Monk Seal (Monachus schauinslandi): Associations with Body Size, Hematology, and Serum Chemistry

Gastrointestinal helminth parasites are found commonly in the Hawaiian monk seal (Monachus schauinslandi), the most endangered seal in the United States and one of the world’s most endangered pinnipeds. We studied potential associations between gastrointestinal helminth infections and body size, and hematologic and serum chemistry variables in a sample of 282 monk seals captured between 1998 and 2002 as part of a population health assessment. Based on the presence of eggs in feces, the highest prevalence of infection (78%) was for cestodes belonging to a complex of several Diphyllobothrium spp. Infections with the nematode Contracaecum turgidum were found in 29% of samples tested. Eggs of the acanthocephalan Corynosoma rauschi were found in 4% of seals examined; and the feces of four weanling seals on the French Frigate Shoals contained eggs of the recently described trematode, Heterophyopsis hawaiiensis. We used a general linear model and analysis of variance techniques with adjustment for subpopulation and age to determine whether infections with Diphyllobothrium spp. or C. turgidum were associated with changes in hematologic or serum chemistry variables and found little evidence of an effect when we compared infected with negative seals or seals in the highest quartile of egg counts with negative seals. We also conducted analyses of associations between infection and morphometric values in adjusted, age-stratified data. Infection with Diphyllobothrium spp. was associated with a decrease in axillary girth and an increase in dorsal standard length/axillary girth ratio in seals less than 2 y of age, with the effects most pronounced in seals less than 1 y of age. After adjustment for Diphyllobothrium spp., C. turgidum infection was not associated with morphometric parameters. Co-infection with Diphyllobothrium spp. and C. turgidum was not associated with differences in body size greater than those found with diphyllobothriid tapeworm infection alone. These findings suggest that intervention strategies to reduce the prevalence of tapeworm infections in immature Hawaiian monk seals should be considered as a conservation measure for this highly endangered marine mammal.