Melon-headed whales (Peponocephala electra) underwater.

Melon-headed whales are a poorly-known tropical oceanic odontocete. They are only infrequently encountered in Hawaiian waters. In our study we’ve encountered groups an average of every 14 days on the water (every ~1,500 km of search effort). Group sizes are variable, ranging from a single animal to 800 individuals, but typically they are found in the largest groups of any species we encounter (median = 287 individuals). Although they are not the primary focus of our work, for every group we encounter we collect identification photographs (over 30,000 to date), biopsy samples for genetics, stable isotopes and toxicology studies (120 to date), and since 2008 have been deploying satellite tags to examine movements (12 deployed in 2008). In July 2011 we published a paper on results from some of the satellite tagging work – to download a copy click here.

Three melon-headed whales.

Melon-headed whales whales are closely related to false killer whales, short-finned pilot whales and pygmy killer whales, all of which are found in Hawaiian waters. They are most frequently confused with pygmy killer whales.

Download the above for information on how to distinguish between pygmy killer whales and melon-headed whales.

Dorsal fins of two melon-headed whales showing the notches that are used to identify individuals. Jessica Aschettino’s Master’s thesis from Hawai‘i Pacific University used the photos we’ve obtained to assess population size, population structure and movements of individuals. One unexpected finding is that there appears to be two populations of melon-headed whales in Hawai‘i, a large population of individuals that move frequently among the islands that utilizes deep waters, and a small population that is resident to the island of Hawai‘i that uses shallower waters. In September 2011 we published a paper on this work – to download a copy click here.

Melon-headed whales in Hawai‘i spend much of their time during the day logging at the surface resting, as in this photo.

One of the more unusual melon-headed whale encounters we’ve had was an adult female associated with a group of rough-toothed dolphins, and accompanied by a smaller animal that is a hybrid between the two species in our 2017 August Kaua‘i work. Instead of the rounded profile of the head typical of a melon-headed whale, this individual had a sloping forehead reminiscent of a rough-toothed dolphin. The dorsal fin shape was typical for a melon-headed whale, and the pigmentation pattern contained features of both species. Details on this individual were included in this initial report. We later resighted the same pair of animals twice in February 2020, and published details on the resightings in this report.

For more information:

• Baird, R.W., C.J. Cornforth, S.M. Jarvis, N.A. DiMarzio, K. Dolan, E.E. Henderson, S.W. Martin, S.L. Watwood, S.D. Mahaffy, B.D. Guenther, J.K. Lerma, A.E. Harnish, and M.A. Kratofil. 2021. Odontocete Studies on the Pacific Missile Range Facility in February 2020: Satellite-Tagging, Photo-Identification, and Passive Acoustic Monitoring. Prepared for Commander, Pacific Fleet, under Contract No. N62470-15-D-8006 Task Order N6274219F0101 issued to HDR Inc., Honolulu, HI. Download PDF copy. 
• Apprill, A., C.A. Miller, A.M. Van Cise, J.M. U’Ren, M.S. Leslie, L. Weber, R.W. Baird, J. Robbins, S. Landry, A. Bogomolni, and G. Waring. 2020. Marine Mammal Skin Microbiotas Are Influenced by Host Phylogeny. Royal Society Open Science 7: 193046. doi: 10.1098/rsos.192046. Download PDF copy.
• Baird, R.W., D.L. Webster, S.M. Jarvis, E.E. Henderson, S.L. Watwood, S.D. Mahaffy, B.D. Guenther, J.K. Lerma, C.J. Cornforth, A.W. Vanderzee and D.B. Anderson. 2019. Odontocete studies on the Pacific Missile Range Facility in August 2018: satellite-tagging, photo-identification, and passive acoustic monitoring. Prepared for Commander, Pacific Fleet, under Contract No. N62470-15-D-8006 Task Order 6274218F0107 issued to HDR Inc., Honolulu, HI. Download PDF copy
• Yahn, S.N., R.W. Baird, S.D. Mahaffy and D.L. Webster. 2019. How to tell them apart? Discriminating tropical blackfish species using fin and body measurements from photographs taken at sea. Marine Mammal Science doi: 10.1111/mms.12584 Download PDF copy
• Baird, R.W., E.E. Henderson, S.W. Martin, and B.L. Southall. 2019. Assessing Odontocete Exposure and Response to Mid-Frequency Active Sonar During Submarine Command Courses at the Pacific Missile Range Facility: 2016-2018. Prepared for Commander, Pacific Fleet, under Contract No. N62470-15-D-8006 Task Order KB16 issued to HDR Inc., Honolulu, HI. Download PDF copy.
• Baird, R.W., D.L. Webster, S.M. Jarvis, K.A. Wood, C.J. Cornforth, S.D. Mahaffy, K.K. Martien, K.M. Robertson, D.B. Anderson and D.J. Moretti. 2018. Odontocete studies on the Pacific Missile Range Facility in August 2017: satellite-tagging, photo-identification, and passive acoustic monitoring. Prepared for Commander, Pacific Fleet, Pearl Harbor, HI. Download PDF copy
• West, K.L., W.A. Walker, R.W. Baird, D.L. Webster and G.S. Schorr. 2018. Stomach contents and diel diving behavior of melon-headed whales (Peponocephala electra) in Hawaiian waters. Marine Mammal Science doi: 10.1111/mms.12507 Download PDF copy
• Yahn, S.N., R.W. Baird, S.D. Mahaffy and D.L. Webster. 2017. How to tell them apart? Blackfish species discrimination using fin and body morphometrics obtainable from photos at sea. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017. View abstract Download PDF copy
• Forney, K. A., B. L. Southall, E. Slooten, S. Dawson, A. J. Read, R. W. Baird, R. L. Brownell Jr. 2017. Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity. Endangered Species Research doi: 10.3354/esr00820. Download PDF copy
• Martien, K. K., B. L. Hancock-Hanser, R. W. Baird, J. J. Kiszka, J. M. Aschettino, M. Oremus, M. C. Hill. 2017. Unexpected patterns of global population structure in melon-headed whales (Peponocephala electra). Marine Ecology Progress Series doi: 10.3354/meps12203/. Download PDF copy.
• Apprill, A., C.A. Miller, R.W. Baird, J. Robbins, M.E. Niemeyer, G.T. Waring A. Bogomolni and S. Landry. 2015. Comparison of skin microbiomes across 16 marine mammal species. Abstract (Proceedings) 21st Biennial Conference on the Biology of Marine Mammals, San Francisco, California, December 14-18, 2015. View abstract
• Baird, R.W., D. Cholewiak, D.L. Webster, G.S. Schorr, S.D. Mahaffy, C. Curtice, J. Harrison and S.M. Van Parijs. 2015. Biologically important areas for cetaceans within U.S. waters – Hawai’i region. Aquatic Mammals 41:54-64. Download PDF copy
• Foltz, K., R.W. Baird, G.M. Ylitalo and B.A. Jensen. 2014. Cytochrome P4501A1 expression in blubber biopsies of endangered false killer whales (Pseudorca crassidens) and nine other odontocete species from Hawai’i. Ecotoxicology doi: 10.1007/s10646-014-1300-0 Download PDF copy
• Kaplan, M.B., T.A. Mooney, L.S. Sayigh and R.W. Baird. 2014. Repeated call types in Hawaiian melon-headed whales (Peponocephala electra). Journal of the Acoustical Society of America 136:1394-1401. Download PDF copy
• Baird, R.W., D.L. Webster, J.M. Aschettino, G.S. Schorr and D.J. McSweeney. 2013. Odontocete cetaceans around the main Hawaiian Islands: habitat use and relative abundance from small-boat sighting surveys. Aquatic Mammals 39:253-269 Download PDF copy
• Southall, B.L., T. Rowles, F. Gulland, R.W. Baird and P.D. Jepson. 2013. Final report of the Independent Scientific Review Panel investigating potential contributing factors to a 2008 mass stranding of melon-headed whales (Peponocephala electra) in Antsohihy, Madagascar. International Whaling Commission. Download PDF copy
• Baird, R.W., D.L. Webster, S.D. Mahaffy, G.S. Schorr, J.M. Aschettino, and A.M. Gorgone. 2013. Movements and spatial use of odontocetes in the western main Hawaiian Islands: results of a three-year study off O’ahu and Kaua’i. Final report under Grant No. N00244-10-1-0048 from the Naval Postgraduate School. Download PDF copy
• Aschettino, J.M., R.W. Baird, D.J. McSweeney, D.L. Webster, G.S. Schorr, J.L. Huggins, K.K. Martien, S.D. Mahaffy, and K.L. West. 2011. Population structure of melon-headed whales (Peponocephala electra) in the Hawaiian Archipelago: evidence of multiple populations based on photo-identification.Marine Mammal Science doi: 10.1111/j.1748-7692.2011.00517.x. Download PDF copy
• Woodworth, P.A., G.S. Schorr, R.W. Baird, D.L. Webster, D.J. McSweeney, M.B. Hanson, R.D. Andrews and J.J. Polovina. 2011. Eddies as offshore foraging grounds for melon-headed whales (Peponocephala electra). Marine Mammal Science doi: 10.1111/j.1748-7692.2011.00509.x Download PDF copy
• Aschettino, J.M. 2010. Population size and structure of melon-headed whales (Peponocephala electra) around the main Hawaiian Islands: evidence of multiple populations based on photographic data.M.Sc. Thesis, Hawai‘i Pacific University. 117 pp. Download PDF copy (this is a 13 MB file so you may need to right-click to download it)
• Baird, R.W., J.M. Aschettino, D.J. McSweeney, D.L. Webster, G.S. Schorr, S. Baumann-Pickering and S.D. Mahaffy. 2010. Melon-headed whales in the Hawaiian archipelago: an assessment of population structure and long-term site fidelity based on photo-identification. Report prepared under Order No. JG133F09SE4440 to Cascadia Research Collective from the Southwest Fisheries Science Center, National Marine Fisheries Service, La Jolla, CA. Download PDF copy
• Aschettino, J.M., R.W. Baird, D.L. Webster, G.S. Schorr, D.J. McSweeney, and J.L. Huggins. 2009. Melon-headed whales (Peponocephala electra) in Hawaiian waters: A look at population size and structure.Talk presented at the 18th Biennial Conference on the Biology of Marine Mammals, Quebec, October 2009.
• Schorr, G.S., R.W. Baird, D.L. Webster, D.J. McSweeney, M.B. Hanson, J. Polovina, and R.D. Andrews. 2009. Satellite tagging of melon-headed whales in Hawai‘i reveals widely dispersed movement patterns. Talk presented at the 18th Biennial Conference on the Biology of Marine Mammals, Quebec, October 2009.
• Southall, B.L., R. Braun, F.M.D. Gulland, A.D. Heard, R.W. Baird, S.M. Wilkin, and T.K. Rowles. 2006.Hawaiian melon-headed whale (Peponocephala electra) mass stranding event of July 3-4, 2004. NOAA Technical Memorandum NMFS-OPR-31. Download PDF copy
• Huggins, J., R.W. Baird, D.L. Webster, D.J. McSweeney, G.S. Schorr and A.D. Ligon. 2005. Inter-island movements and re-sightings of melon-headed whales within the Hawaiian archipelago. Presentation at the 16th Biennial Conference on the Biology of Marine Mammals, San Diego, CA, December 2005. Download PDF copy of poster
• Ligon, A.D., R.W. Baird, D.L. Webster, D.J. McSweeney, and G.S. Schorr. 2007. Habitat preferences of melon-headed whales (Peponocephala electra) around the main Hawaiian Islands: implications for interpretation of the 2004 Hanalei Bay stranding event. Poster presented at the 17th Biennial Conference on the Biology of Marine Mammals, Cape Town, South Africa, November-December 2007. Download PDF copy of poster

All photos are copyrighted and should not be used without permission.

Updated November 2021.

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Got photos? We have photo-ID catalogs for several Hawaiian cetacean species! If you have photos that you would be willing to share, you can learn how to submit those to us at this link, or contact us at Hawaii@cascadiaresearch.org