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Keywords:

  • melon-headed whales;
  • Peponocephala electra;
  • mass-stranding;
  • mid-frequency sonar;
  • behavior;
  • lunar cycles;
  • Hanalei Bay;
  • Hatihue Bay;
  • Sasanhaya Bay

Abstract

Southall et al. (2006) concluded that a near mass stranding (MS) of melon-headed whales (MHWs), Peponocephala electra, in Hanalei Bay, Kauai, Hawaii, on 3–4 July 2004, was likely related to the operation of mid-frequency sonars (MFS). However, subsequent authors argued that the nearly simultaneous entry of MHWs into Sasanhaya Bay, Rota (∼5,740 km away) made this conclusion untenable. They suggested that both sightings, and other MSs of MHWs, could be related to lunar cycles. To resolve this question, we reviewed information on the biology and behavior of MHWs and compared the two sightings to observations of MHWs around Palmyra Atoll and Nuku Hiva, French Polynesia. We also tested for a relationship between observations and MSs of MHWs with lunar cycles. MHWs near many oceanic islands rest nearshore during the day and feed offshore in deeper water at night. The MHWs at Rota exhibited normal diurnal resting behavior as seen at Palmyra and Nuku Hiva, while those at Kauai showed milling behavior typically seen prior to MS events. Thus, these events were not similar. Neither observations nor MSs of MHWs were related to lunar cycles. Our review of MHW behavior strengthens the case that MFS use played a major role in the near MS in Hanalei Bay.