ESR 20:137-146 (2013)  -  DOI: https://doi.org/10.3354/esr00491

Dietary comparison of two Hawaiian monk seal populations: the role of diet as a driver of divergent population trends

M. K. Cahoon1,*, C. L. Littnan2, K. Longenecker3, J. R. Carpenter4

1Joint Institute for Marine and Atmospheric Research, 1000 Pope Road, Honolulu, Hawaii 96822, USA
2Pacific Islands Fisheries Science Center, National Marine Fisheries Service, NOAA, 1601 Kapiolani Boulevard, Honolulu, Hawaii 96814, USA
3Bishop Museum, 1525 Bernice Street, Honolulu, Hawaii 96817, USA
4Department of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa, 1955 East West Road, Honolulu, Hawaii 96822, USA

ABSTRACT: Divergent trends in population abundance of Endangered Hawaiian monk seals Monachus schauinslandi are apparent between the northwestern Hawaiian Islands (NWHI) and the main Hawaiian Islands (MHI). The smaller, recently established MHI seal population is increasing, exhibits higher juvenile survival, and seals appear to be in better condition overall relative to seals in the NWHI. Using traditional dietary analysis we characterize the diet of MHI monk seals for the first time and examine the hypothesis that diet and prey availability may be driving these regional trends. Prey remains from feces and regurgitates (n = 120) were identified to the lowest possible taxonomic level and compared with results from NWHI historical data. The most common prey taxa, by percent frequency of occurrence, were Balistidae (48.3%), Crustacea (37.5%), Acanthuridae (32.5%), Muraenidae (30.8%), Serranidae (20.8%), Cephalopoda (18.3%), Holocentridae (17.5%), Labridae (16.7%), and Scaridae (10.8%). Results indicate that MHI and NWHI seals eat similar diets; however, an incongruity in body conditions of seals between regions indicates a possible difference in intra- or inter-specific competition, prey availability, and quality. Further research assessing foraging behavior and habitat use would aid in identifying the regional differences observed.


KEY WORDS: Monachus schauinslandi · Fecal prey remains · Diet assessment · Hawaiian Islands


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Cite this article as: Cahoon MK, Littnan CL, Longenecker K, Carpenter JR (2013) Dietary comparison of two Hawaiian monk seal populations: the role of diet as a driver of divergent population trends. Endang Species Res 20:137-146. https://doi.org/10.3354/esr00491

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