Beaked Whale Survey

One quarter of the world's 80 whale and dolphin species belong to the family of beaked whales, but because they favor deepwater habitat, study and knowledge of these cetaceans is in its infancy. What little is known of beaked whales has largely come from stranded animals. Sightings of these elusive creatures at sea are extremely rare due to their long dive times and unobtrusive surfacing behavior. In the past few years, however, biologists in several parts of the world have finally been able to study these elusive animals at sea.

The Cook Islands is a nation of 15 atolls and islands scattered over 850,000 square miles of the central South Pacific between latitudes 22°S and 10°S. The islands' steep topography and surrounding abyssal depths lend themselves to beaked whale habitatation. However, until 1999, there were no confirmed sightings of beaked whales in the Cook Islands. In August, 1999, while running humpback surveys, Cook Islands Whale Research encountered two groups of beaked whales, one off Aitutaki and the other off Rarotonga. Local fishermen recognized the beaked whales when shown footage and photographs.

Four or more beaked whales have stranded in the Southern Cook Islands since 1988. At least two have stranded on Rarotonga since 1988. Two more stranded at Manuae in 1998. The Rarotonga specimens were identified as Ziphius cavirostris (Cuvier's beaked whale) and Mesoplodon densirostris (Dense-beaked whale) through extensive morphological analysis by Gerald McCormack of CINHT. Efforts are underway to retrieve the skeletons from isolated Manuae, which have tentatively been identified as Ziphius cavirostris from photographs taken by visiting fishermen. A tooth was collected from one of the Manuae whales in 1998. Shavings from this tooth and from the teeth of the two Rarotonga whales have been analyzed to definitively identify the species using molecular genetic techniques by associates at the University of Auckland.

A sightings network has been coordinated with local vessel operators, primarily fishermen, and aircraft pilots.

OBJECTIVES:

The objectives of this pilot survey are to:

• ascertain presence of beaked whales off Rarotonga in summer
• photo-identify all individuals encountered using 35mm and digital video surface and underwater
• evaluate prospects for biopsy sampling of beaked whales
• involve and engage Cook Islanders in research process to further their understanding of and commitment to marine conservation through public outreach and internships